The reticular frameworks have crystalline and extended porous structures, which can not only orderly organize a variety of building blocks to form mesoscopic materials in a programmable way, but also perform an excellent platform for basic scientific research because of the regulatable and precise structures. The representative systems of reticular frameworks are metal organic frameworks (MOFs) and covalent organic frameworks (COFs). Mechanically interlocked structures are molecular aggregations interacted through mechanical bond to realize complex functions. The combination of reticular frameworks and mechanically interlocked structures can promote the basic research of the microscopic interlocked behaviors in solid states; and also organize the interlocked structures in a regular way to achieve more complex functions. The mechanically interlocked structures can be introduced into reticular frameworks in two strategies, using mechanically interlocked structures as building blocks participating in the construction of reticular frameworks; and forming woven or interlocked frameworks with whole interlocked skeleton from unlocked precursors. This review summarizes the important progresses in the emerging research field combining the reticular frameworks and mechanically interlocked structures. In the first section, after the brief introduction of reticular frameworks and mechanically interlocked structures respectively, the significances and strategies of the combination of the above two fields is described. In the second section, we reveal the systematic and representative research of mechanically interlocked structure as a part of building blocks participating in the construction of reticular frameworks, including rotaxane, shuttle and catenate. The mechanical motions of rotaxanes and shuttle within MOFs are intensively studied. The representative methods and structures of introducing rotaxane or catenate into reticular frameworks are presented. In the third section, we exhibit the reticular frameworks constructed through mechanical bond as the main interaction within the whole skeleton from unlocked precursors, including resilient woven frameworks and mechanically interlocked frameworks. The typical woven or interlocked frameworks are mostly templated from special metal complexes and showing reversible transition between crystal and non-crystal maintaining the whole interlocked skeleton. Finally, we summarize the whole paper and discuss the future development in this crossing field, such as the applications of these combined systems should be expanded and the mechanically interlocked frameworks constructed through interlocking discrete molecular rings are expected due to the potential excellent elastic properties.

Cyclodextrins (CDs) are a family of macrocyclic oligosaccharides composed of α-1,4-linked D-glucopyranose units. The most commonly used CDs are α-, β-, and γ-CD, which consist of 6, 7, and 8 D-glucose units, respectively. They possess a relative hydrophobic inner cavity and a hydrophilic outer surface and can form inclusion complexes with various small molecules, metal ions and polymers, tailoring the physicochemical property of the guests, and thus have been widely used in the fields of pharmacy, food, chemistry, chromatography, catalysis, biotechnology, agriculture, cosmetics, hygiene, medicine, textiles and the environment, etc. However, it is difficult to manipulate the native CDs in some specific applications, they are crystallized solid and soluble in water but insoluble in most organic solvents. CD polymers (CDPs), such as crosslinked CDs or CD based hydrogels with various crosslinkers by chemical reactions, and CD based supramolecular polymers formed by physical interactions, can achieve the integration effect and synergy effect of CDs, crosslinkers and guest polymers, not only possessing the inclusion capacity of CDs, but also endowing CDs with other properties introduced by crosslinkers. The CDPs can be easily manipulated and they exhibit unique features that native CDs are lack of. Hence, the design, synthesis and applications of CDPs have attracted broad interests in recent years. This review focuses on the recent progress in CDPs, and different types of CDPs are identified and classified based on the structures and functions, namely CD based polyrotaxane, grafted CDs, crosslinked CDs and linear CDs, etc. Besides, the synthetic methodologies of CDPs are highlighted. Particular attention is paid to the breakthrough on the CDPs in the past five years, and their applications in biomedicine, such as drug delivery, gene delivery, target delivery, controlled release and cell imaging are discussed in detail. The typical applications in other fields such as absorption, environment remediation, thermal insulation, catalysis and slid-ring gels are also discussed in brief. Finally, the review provides brief summary and prospect of CDPs.

Surgical sutures, staples and clips have been widely used for wound closure, tissue reconstruction and tissue adhesives are one of the versatile alternatives especially for friable tissues. Some synthetic and semisynthetic tissue adhesives are available elsewhere. However, there are some drawbacks, such as poor adhesion on wet substrates and potential toxicity, for the reported tissue adhesives. Fibrin glues as biological tissue adhesives are effective hemostatic agents while presenting relatively weak tensile and adhesion strengths and being expensive. Biomimetic adhesives as tissue adhesives, hemostatic agents, or tissue sealants have attracted great attention for clinical operations in last three decades. However, engineering of bio-adhesive materials with good water resistance, high adhesive strength, and good biocompatibility and multi-functionality remains a challenge for tissue healing. Since the first report of mussel-inspired surface chemistry for functional coatings of polydopamine by the Messersmith group in 2007, materials containing plenty of phenolic hydroxyl groups have been widely used in medical applications, food, cosmetics, water treatment and so on, due to the antioxidant, antibacterial, and anti-inflammatory effects of polyphenols. Polyphenol-based hydrogel is an ideal bio-adhesive material due to its good tissue adhesion even on wet substrates, hemostatic and antimicrobial capabilities. Moreover, these hydrogels with porous structures have similar physiochemical properties to that of natural extracellular matrix and different shapes from nanometer to centimeter scales can be remolded to seal irregular defects on tissues. In this review, we report the recent progress of the engineering of polyphenol-synthetic polymer hydrogels, polyphenol-biomacromolecule hydrogels, polyphenol-inorganic nanocomposite hydrogels, and polydopamine nanoparticle composite hydrogels, as well as their applications of tissue adhesives, hemostasis, antimicrobials for wound closure and tissue regeneration. The challenges as well as prospects for future development of polyphenol-based tissue adhesives, sealants, hemostatic agents are also summarized and discussed, which is helpful to promote the next generation of tissue adhesives for biomedical applications.

Imines and the intermediate methylamine by the aldimine condensation of primary amines with aldehydes have a potential application in the field of pharmacy, life science, catalysis, material science, etc. In this reaction, the hydrogen transfer in the dehydration step normally prefers the pathway via a water bridge in aqueous solution or a directly dehydration in organic solvent. It is a different mechanism for the aldimine condensation of amine owning neighbouring nitrogenous heterocycle. Herein we investigated the mechanism of aldimine condensation of primary amine containing nitrogenous heterocycle with aldehyde in dichloromethane under acidic conditions using density functional theory (DFT) at ωB97X-D/6-31++G(d,p) level, the calculated results show that compared with specific acid catalysis, the heterocyclic nitrogen with stronger basicity is easier to be protonated than the oxygen of carbonyl group. The whole reaction proceeds two hydrogen transfer steps via nitrogen bridge owning an energy span of 13.08 kcal/mol. The rate-determing step is the second hydrogen transfer step. In each step the heterocyclic nitrogen is a bridge to assist the hydrogen transfer, which could reduce the free energy barrier of the aldimine condensation. It is unfavorable for the reaction pathway via directly hydrogen transfer with a four-membered ring transition state owning a free energy barrier of 32.73 kcal/mol, and the reaction pathway via a water bridge is not located. Meanwhile, the energy barriers increased for systems in which the N atom in heterocycle of primary amine is replaced by P/As atoms. The rate-determining step changes from the second hydrogen transfer step for N system to the first hydrogen transfer step for As system. The position effect of adjacent nitrogen atom is also investigated. The γ position owns the highest reactivity of the aldimine condensation, which implies that the ring strain plays an important role in the aldimine condensation of primary amine containing nitrogenous heterocycle with aldehyde. This theoretical study may provide insights to unveil the nature of aldimine condensation of aldehyde and primary amine owning nitrogeneous heterocycle.

During the past decade, transition metal-catalyzed dehydrogenative cross-couplings have emerged as an attractive strategy in synthetic chemistry due to its high step- and atom-economy as well as the less functionalized coupling partners. However, such reactions have to always use stoichiometric amount of sacrificial oxidants such as peroxides, high-valent metals (Cu salts, Ag salts, etc.), or iodine(III) oxidants, thereby leading to possible generation of toxic wastes and making the process less desirable from a green chemistry perspective. The recently developed photocatalytic CCHE (cross-coupling hydrogen-evolution) reactions are a conceptually new type of reactions enabled by combination of photo-redox catalysis and proton reduction catalysis, wherein the photocatalyst uses light energy as the driving force for the cross-coupling and the hydrogen evolution catalyst may capture electrons and protons from the substrates or reaction intermediates to produce molecular hydrogen (H₂). Thus, without use of any sacrificial oxidant and under mild conditions, the dual catalyst system may afford cross-coupling products with excellent yields and an equivalent amount of H₂ as the sole byproduct. This kind of cross-coupling delivers a greener synthetic strategy and is particularly useful for reactions that involve species sensitive to traditional oxidants. In CCHE reactions, the raw materials are directly converted into products and hydrogen, the reactions are highly atom economy, environmentally friendly, and have attractive potential industrial application prospects. In this review, recent dramatic developments of photocatalytic and electrochemical CCHE reactions are discussed via the most prominent mechanistic pathways, the types of C-C bond, C-X (heteroatom) bond, or X-X bond formations and specific reaction classes.

Precisely modulating the structure of nanoparticles in a controlled manner is still a challenging and inspiring topic. Although the single or few-metal atom tailoring of gold nanoparticles has been reported, local structural replacement involving over three net metal atoms (module replacement, MR) has not been hitherto achieved. Herein, we report the synthesis of cyclohexanethiolated metal nanoclusters (NCs) Au₄₈(CHT)₂₆ and their MR by a so-called pseudo-anti-galvanic reaction (AGR) process. The MR product Au₃₇(CHT)₂₃ shares a similar Au₃₁(CHT)₁₂ unit with its predecessor Au₄₈(CHT)₂₆; however, it differs from its predecessor in the remaining section (Au₆(CHT)₁₁ vs. Au₁₆(CHT)₁₄), as revealed by single-crystal X-ray crystallography (SCXC). Interestingly, the MR inhibits the photothermy but enhances the emission of Au₄₈(CHT)₂₆ NCs, which might endow the as-obtained NC better potential for bi(multiple)-functional application. The counter effects of the MR on the emission and photothermy indicate that photoluminescence and photothermy can be at least partly converted into each other, which has some important implications for the understanding of their interaction.

photocatalytic pollutant degradation and the synthesis of chemical fuels or other high value-added products via photocatalysis have drawn plenty of attentions in green chemistry and renewable energy research. In recent years, metal-halide perovskites with superior photoelectric properties are successfully utilized into high-efficiency photocatalytic reactions in addition to conventional metal oxide semiconductor materials. In this paper, we reviewed the recent advances of metal-halide perovskite based photocatalyst, especially lead-halide perovskites in photocatalytic hydrogen production, photocatalytic degradation and CO₂ reduction. The reaction mechanisms and key challenges for metal halide perovskites photocatalyst are discussed and we prospect the further development of highly efficient and stable metal halide perovskite photocatalysis in the future.

P-Chiral phosphine oxides are a class of privileged structures, which have important applications in the field of medicinal chemistry, organic synthesis, life and material science. Recent years have witnessed significant progress in the catalytic asymmetric construction of such scaffolds. These advances are summarized in this review according to the following three major strategies:desymmetrization of prochiral tertiary phosphine oxides, (dynamic) kinetic resolution of tertiary phosphine oxides, and catalytic asymmetric reactions involving secondary phosphine oxides, and discusses the possible reaction mechanism, the advantage and disadvantage of each type of reactions, which would provide reference and inspiration for the researchers engaged in organic synthesis and organic phosphorus chemistry.

Near infrared II (NIR Ⅱ, 1000~1700 nm) biological imaging, as a new developing optical imaging technology in recent years, has longer fluorescence wavelength compared with the traditional near infrared I (NIR I, 750~900 nm) and visible light (Vis, 400~750 nm) imaging. Due to the longer emission wavelength, weaker interference by light scattering and tissue autofluorescence, result in higher temporal and spatial resolution with deeper tissue penetration. This technology is more suitable for in vivo imaging in situ. In this review, we mainly introduced research progress on NIR II instrument technology for in vivo imaging, and summarized its major features. Finally, we provided a prospect that the development of chemical materials, optoelectronic instruments, and multi-modal technologies can promote NIR II technology innovation, which is expected to be widely and deeply applied in clinical transformation.

In recent years, the efficiency of perovskite solar cells has developed rapidly, but its stability is limited by the influence of heat, light and water. All-inorganic perovskite formed by inorganic cations instead of organic cations shows improved thermal stability, high light absorption and adjustable band gap. The photoelectric conversion efficiency of all-inorganic perovskite solar cells has been improved to 19.03% at present. Among them, CsPbI₃ perovskite solar cells have good photoelectric performance but poor stability, while CsPbBr₃ perovskite solar cells have excellent stability but poor photoelectric performance of devices. In this paper, the influence of preparation method, film doping and interface modification on the stability of inorganic perovskite solar cells is systematically summarized. The reasons behind the instability of inorganic perovskite and the improvement methods are emphatically analyzed. In conclusion, improving the stability of inorganic perovskite light absorbing materials by film doping, surface passivation and morphology control such as low dimensional materials preparation can effectively improve the stability of the overall device, which provides the basis for further commercialization. In addition, it is of great significance to study the theory of charge transfer and recombination and establish a complete theoretical system for improving the performance and stability of the device. At present, most of perovskite contains harmful elements Pb. How to replace Pb and find new materials applied in perovskite solar cells is also the future development trend. In a word, as a new type of solar cell, inorganic perovskite solar cell is expected to contribute to the photovoltaic development of the future society.

Transition metal-catalyzed direct C-H functionalization is one of the most efficient and powerful tools for the rapid synthesis of organic molecules. The use of functional groups in the molecules or covalently attached coordinating groups as directing groups has been realized as a major strategy to control the selectivity. Noncovalent interactions are of great importance in the field of molecular biology, supramolecular chemistry, material science and drug discovery. More recently, the use of well-designed ligands to enable the site-selective C-H functionalization via noncovalent interactions has emerged as a highly promising yet relatively less explored strategy. In this perspective, recent advances in this cutting-edge area are summarized. The perspective was classified into four sections according to the type of noncovalent interactions, including hydrogen bonding, ion pair, Lewis acid-base interaction and electrostatic interaction. Emphasis is placed on the mode of noncovalent interactions among the transition metals, ligands and substrates. The limitation of current research and the prospect of future work will also be discussed. We anticipate that this strategy might become a promising complementary strategy to control the positional selectivity in C-H functionalization reactions.

The study on the reaction mechanism of organonitrile and sodium azide catalyzed by transition metals has always been a challenging and controversial task. Due to the difficulty in capturing the reaction intermediates, there is still no direct evidence to uncover the nature of the reaction. In this paper, the reaction mechanism has been explored by using a combining theoretical and experimental method. Based on the theoretical analysis of the stability of two types of intermediates (H₂O)₃M…N₃^- and (H₂O)₃M…NCCH₃ and the successful capture of two activated intermediates containing metal cadmium ions Cd₂(μ₃-N₃)(μ₃-OH)(μ₅-CHDA) (1) and Cd(μ₂-N₃)(μ₃-IBA) (2) (H₂CHDA=1,3-cycloadipic acid and HIBA=4-(imi-dazol-1-yl) benzoic acid), which were achieved under the hydrothermal conditions and characterized by single-crystal XRD analysis. For the first time, the experimental and theoretical results reveal that the transition metal ions activate the azide rather than the cyano group of nitriles. In addition, the results of both the electrostatic potential basins analysis of activated intermediates (H₂O)₃M…N₃^- and acetonitrile molecules obtained by the theoretical calculation and our recently reported experimental results reveal that the intermediates (H₂O)₃M…N₃^- can be used as electrophilic reagent. Its uncoordinated terminal N atom can attack the N atom of the cyano group of acetonitrile to undergo a nucleophilic addition reaction during the chemical reaction progress, and then it may undergo a[2+3] cycloaddition reaction to in-situ form tetrazole. Moreover, with the aid of water molecules, its adducts may also occur similar to the Ritter-like reaction to in-situ form polynitrogen anion. Our findings may open a novel field of the in-situ synthesis of polynitrogen compounds based on the transition metal-catalyzed reactions of organonitrile and azide.

The selective oxyfunctionalization of unactivated C-H bonds is one of long-standing issues and current topics in synthetic chemistry. One of the major synthetic targets for these reactions is the direct and selective hydroxylation of alkanes to alcohols, however, which faces many severe challenges in controlling chemoselectivity, regioselectivity and stereoselectivity. In nature, the oxidative metalloenzymes is capable of selectively catalyzing the insertion of oxygen into inert C-H bonds of alkanes, such as methane monooxygenases (MMO), soluble butane monooxygenases (sBMO), fungal peroxygenases and Cytochrome P450 monooxygenases (P450s). Among them, P450s that catalyze a variety of oxygenation reactions have attracted special attentions because of some intrinsic advantages. P450s are widely distributed in plants, animals and microorganisms and over 41000 sequences of P450 genes have been named from various databases, which enhances the potentials of P450s in developing the oxidative biocatalysts. In addition, compared with MMOs, P450s that have smaller molecule weight (≈45 kDa) are simple and amenable to recombinant expression and engineering. Herein, we reviewed the recent progress of alkanes hydroxylation by P450 enzymes either in its natural forms or engineered variants, as well as chemical activated systems. The related background and the catalytic mechanism of P450s for alkanes hydroxylation were firstly discussed. The representative examples by natural P450s mainly from CYP153, CYP52 and other P450 families were then outlined. The strategies of rational design and directed evolution on P450s engineering were then summarized focusing on the native/non-native alkane substrates. Three unusual strategies, including substrate engineering, decoy molecule, and dual-functional small molecule co-catalysis, were also discussed on their applications for activating P450s to hydroxylate non-native small alkanes. Finally, we perspective the challenges and solutions that faced by P450 enzymes in the development of new biocatalytic systems toward selective hydroxylation of alkanes. In conclusion, cytochrome P450 enzymes in both of their native and modified form are promising biocatalysts for alkanes hydroxylation and need further be investigated to gain the practical industrial applications.

Metal-organic frameworks (MOFs), a class of promising heterogeneous catalysts, though readily recyclable, usually suffer from poor dispersity and ease of sedimentation in liquid-phase reaction systems, which may lead to limited exposure of active sites and unsatisfied activity. Conventional hydrothermal synthesis often results in large MOF particles in bulk form and poor dispersity. The homogenization of MOF catalysts is an exciting but challenging task to integrate the advantages of both homogeneous and heterogeneous catalysts. Herein, by means of microwave-assisted synthetic approach, a soluble porphyrinic MOF, denoted as S-Al-PMOF, has been successfully fabricated. In contrast to the Bulk-Al-PMOF synthesized by the conventional hydrothermal route, which requires 180℃ and 16 h, the S-Al-PMOF obtained by the microwave-assisted method is very efficient and takes 30 min only at 140℃. While the as-synthesized S-Al-PMOF can be completely soluble in acetonitrile by ultrasonic dispersion to give a clear and transparent colloidal solution, the Bulk-Al-PMOF can form a turbid suspension liquid by continuous stirring, which easily aggregate with sedimentation in a short time after standing. Furthermore, the S-Al-PMOF can be easily separated from the solution by suction filtration and then re-dissolved in acetonitrile. This separation and re-dissolution process can be repeated several times to prove its good recovery and recycling. Given the outstanding light harvesting ability of Al-PMOF, photocatalytic H₂ production by water splitting has been adopted to examine the activity of both S-Al-PMOF and Bulk-Al-PMOF. As a result, the activity of S-Al-PMOF is around 14 times higher than that of Bulk-Al-PMOF, owing to excellent solubility of the former. Moreover, S-Al-PMOF also exhibits good recyclability in the consecutive three cycles of reaction. We believe that the successful synthesis of soluble Al-PMOF opens a new avenue to the homogenization of heterogeneous catalysts.

With the accelerating process of industrialization and urbanization, as well as the increasing proportion of the elderly in the world's population, we are facing more complex health threats related to bacterial infection. While the vast majority of the bacteria in the body are rendered harmless by the protective effects of the immune system, the continued abuse and misuse of antibiotics has accelerated the spread of antibiotic-resistant bacterial strains and has resulted in substantial new challenges with respect to modern-day antibiotic-based treatments. Therefore, intelligent design of new antibacterial modalities to be used for treating human and livestock diseases is an extremely urgent priority for researchers in the fields of chemistry, chemical engineering, materials and biomedical sciences. Toward this end, the most intriguing of the new developments are metal-organic frameworks (MOFs). MOFs are versatile crystalline porous lattices of organic ligands and metal ion/clusters that formed by self-assembly via coordination bonds. Due to their unique characteristics, including relatively straight forward and simple methods for synthesis, large surface areas, novel and diverse structures, and adjustable porosity, MOFs not only play strong roles with respect to novel methods for gas storage and separation, they may also be utilized in unique applications associated with sensors mechanisms and catalysis. These features contribute to our current understanding of MOFs as promising candidates for the development of pharmaceutical and specifically antibacterial applications. In this review, antibacterial mechanisms, and the development of resistance to current antibiotic strategies are summarized and discussed. The main mechanisms by which bacteria show resistance to antibiotics include altered metabolic pathways, regulation of target sites, and inactivation, modification, and/or reduction in the capacity to accumulate antibacterial drugs. We consider recent progress on the development of MOFs, including the use of specific metal centers and ligands, metal nanoparticles, and drug-encapsulation, all of which have important applications with respect to antibacterial activities, and wound healing. Finally, the challenges and prospects of MOF-based antibacterial materials are discussed, including critical findings, which will help toward the development of the next generation antibacterial MOFs for human use.

In metallocene-mediated propylene polymerization, β-methyl elimination (β-Me elimination) is considered as the key chain-release step for obtaining allyl-terminated products, which are highly preferred as macro(co)monomers or building blocks for preparing novel polymers. However, for most metallocene catalysts the transfer of a β-methyl is instinctively less favored due to its steric and electronic disadvantages. Up to date, very few cases have been found to be efficient for triggering selective β-methyl elimination. In this work, a series of novel ansa-metallocene complexes, ansa-C₂H₄-{2-Me-3-Bn- 5,6-[1,3-(CH₂)₃]Ind}(Flu)ZrCl₂ (C1), ansa-C₂H₄-{2-Me-3-Bn-5,6-[1,3-(CH₂)₃]Ind}(2,7-^tBu₂-Flu)ZrCl₂ (C2), ansa-C₂H₄-{2-Me-3-Bn-5,6-[1,3-(CH₂)₃]Ind}(3,6-^tBu₂-Flu)ZrCl₂ (C3) and ansa-C₂H₄-{2-Me-3-Bn-5,6-[1,3-(CH₂)₃]Ind}(Flu)HfCl₂ (C4), were synthesized via the reaction of the dilithium salts of the corresponding proligand with 1 equiv. of ZrCl₄ or HfCl₄ in Et₂O. All complexes were characterized by ¹H NMR, ¹³C NMR and elemental analysis. The molecular structures of complexes C1, C2, and C3 were further determined via X-ray diffraction method. In the solid state, these complexes adopted an indenyl-backward orientation with rotation angles (RA: the orientation of the indenyl ring with respect to the fluorenyl ring) ranging from －11.30° to －17.07°. Upon activation with modified methylaluminoxane (MMAO) or AlⁱBu₃/ [Ph₃C][B(C₆F₅)₄] (TIBA/TrB), all these complexes exhibited moderate to high activities for propylene oligomerization at 40～100 ℃, affording propylene oligomers with both allyl and vinylidene chain-ends, which arised from β-Me elimination and β-H eliminations respectively. The methyl group at the 2-position of the indenyl ring turned out to have negative effects on both catalytic activity and β-Me elimination selectivity. Zirconocene complex C1 polymerized propylene to give oligomers with 40%～52% allyl chain-ends. However, further modification of the fluorenyl moiety allowed a great improvement in β-Me elimination selectivity. At 40～100 ℃, zirconocene complexes C2 and C3 bearing a 2,7- or 3,6-di-tert-butyl- substituted fluorenyl moiety showed significantly higher β-Me elimination selectivities (C2, 81%～86%; C3, 68%～77%), affording propylene oligomers (M_n 400～4500 g·mol^－1) with allyl-dominant chain-ends. Moreover the substitution pattern of the fluorenyl moiety also substantially influenced the catalytic activities. The incorporation of an electron-donating 2,7-di-tert-butyl groups on the fluorenyl moiety led to notably increased catalytic activities of complex C2 at higher temper- atures above 60 ℃, while complex C3 bearing a 3,6-di-tert-butyl-substituted fluorenyl moiety showed lowest activities among the zirconocene series due to its overcrowded coordination sites. Compared with its zirconocene analogue, the hafnocene complex C4 activated with TIBA/TrB proved to be even more selective toward β-Me elimination, and meanwhile gave products with much lower molecular weights. At 100 ℃, the hafnocene system mainly oligomerized propylene to dimers and trimers. Studies on the dependence of the product molecular weight and the chain-release selectivity on monomer concentration suggested that both β-Me and β-H elimination involved in these systems mainly operate in a bimolecular pathway.

Covalent organic framework materials (COFs) are a class of organic porous materials with large specific surface area, high porosity and crystallinity. Owning to their special nature of functional versatility and easy modification, COFs can be designed to be efficient catalysts either embed functional active sites into the skeleton through a "top-down" strategy, or load metal nanoparticles into the framework via a post-modification approach. These studies have laid the foundation for the extension of COF's application in heterogeneous and other catalytic fields. The synthetic strategy and application of COF in different types of catalytic reactions are reviewed in this paper. Moreover, the current research situation of COF catalyst is summarized and prospected. Finally, the remaining challenges in this field are also indicated.

Recovering C₂H₄ from refinery gas is an effective way to broaden the source of ethylene. However, it's a challenging task to separate C₂H₄ and C₂H₆ due to their very close physical properties and molecular size. Metal-organic frameworks (MOFs) are shown broad prospects in the field of light hydrocarbon separation in recent years. In this work, NH₃ is used to modify the structure of UTSA-280, the efficient separation of C₂H₄/C₂H₆ can be achieved through the adjustment of one-dimensional channels. UTSA-280 has undergone stepwise adsorption of ammonia gas at 298 K and 100 kPa. After partial ammonia removal, we obtained the modified UTSA-280 that ammonia adsorption modification with a mass loading of 5.6% for UTSA-280-M1 and 2.8% for UTSA-280-M2. The NH₃ modified UTSA-280 shows a unique ultramicroporous structure that can enhance the adsorption of C₂H₄ and does not adsorb the slightly larger C₂H₆, achieving the ideal C₂H₄/C₂H₆ adsorption selectivity (more than 1000). Ammonia molecules play the role of perfectly adjusting the size of one-dimensional channels and realize the ideal screening effect of C₂H₄/C₂H₆. The C₂H₄ adsorption capacity of NH₃ modified UTSA-280-M2 can be improved to 2.83 mmol/g at 298 K and 100 kPa (an increase of 29% compared with initial material). And its ultramicroporous structure can fully block the adsorption of C₂H₆, which finally achieves a C₂H₄/C₂H₆ selectivity over 1200. Grand Canonical Monte Carlo (GCMC) simulation of C₂H₄/C₂H₆ mixed gases (equal volume) adsorption results showed that the modified UTSA-280 had more C₂H₄ adsorption distribution in the mixed components than C₂H₆. Through the C₂H₄/C₂H₆ mixed gases breakthrough test at 298 K, NH₃ modified UTSA-280-M2 shows a separation time of more than 48 min, which is more than the initial 25 min. Compared with the unmodified material, the separation performance is nearly doubled. Scalable synthesis, stable structure, and the advantages of controllable performance after ammonia modification have prompted this material to have great prospects in the industrialization of C₂H₄/C₂H₆ separation.

Azulene, a bicyclic nonbenzenoid aromatic hydrocarbon, shows completely different physicochemical properties compared with its isomeric naphthalene. Herein, we made use of the diverse reactivity of each position on azulene to design a new synthetic strategy for azulene-based diimides bridged by phenyl or thieno[3,2-b]thiophenyl group, 2-(azulen-2'-yl)-5-(azulen-2''-yl)benzene-1,1':4,1''-tetracarboxylic diimides (AzAzBDI-1/2) and 2-(azulen-2'-yl)-5- (azulen-2''-yl)thieno[3,2-b]thiophene-3,1':6,1''-tetracarboxylic diimide (AzAzTTDI). The key step was double trifluoroacetylation at 1-position of two azulene moieties of the molecule followed by hydrolysis, anhydridization and imidization to obtain the target compounds. The single crystal structure analysis demonstrates that AzAzBDI-2 has twisted molecular backbone. The adjacent two molecules form a dimer through the intermolecular π-π stacking (0.365 nm) between the five-membered ring and the seven-membered ring of two different azulene units. Strong π-π intermolecular interactions (0.355 nm) exist among the dimers to form a slipped one-dimensional (1D) packing motif in the crystal. For three compounds, the optoelectronic properties were investigated by UV-vis absorption spectra and cyclic voltammetry, and their energy levels of highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) and the energy gaps were calculated. The HOMO/LUMO energy levels of AzAzBDI-1, AzAzBDI-2 and AzAzTTDI are －5.56/－3.28 eV, －5.56/ －3.30 eV and －5.57/－3.42 eV, respectively. The end absorptions of AzAzBDI-1, AzAzBDI-2 and AzAzTTDI in thin films show obvious red-shift (13, 13 and 25 nm) relative to those in CHCl₃ solution, indicating strong intermolecular interactions in solid state. The charge carrier transport properties of three compounds were studied through organic field-effect transistors (OFETs). Bottom-gate and top-contact OFET devices of AzAzBDI-1, AzAzBDI-2 and AzAzTTDI were fabricated by spin-coated their respective solution on octadecyltrimethoxysilane (OTMS)-treated SiO₂/Si substrates. Under nitrogen atmosphere, all of these three compounds displayed electron-dominated ambipolar organic semiconductor characteristics. The electron mobilities of AzAzBDI-1 and AzAzBDI-2 were 0.068 cm²·V^－1·s^－1 and 0.086 cm²·V^－1·s^－1 and the hole mobility were 3.1×10^－4 cm²·V^－1·s^－1 and 1.5×10^－3 cm²·V^－1·s^－1, respectively. OFETs based on AzAzTTDI showed the highest electron mobility and hole mobilities of 0.087 cm²·V^－1·s^－1 and 8.8×10^－3 cm²·V^－1·s^－1, respectively. The X-ray diffraction (XRD) and atomic force microscopy (AFM) studies demonstrate thin films of AzAzBDI-1, AzAzBDI-2 and AzAzTTDI show better crystallinity and form larger size of microstructures by annealing, which is consistent with the enhanced device performance after thermal annealing.

Organic solar cells have been developing quite rapidly in the past two decades. Tang fabricated the first organic solar cell with planar heterojunction in 1986, while the power conversion efficiency (PCE) was only 1%. The PCE of single-junction organic solar cell has increased to over 17% in 2019. However, the single-junction solar cells are limited in performance by the severe energy loss. Tandem organic solar cells that use an interconnecting layer connecting two sub-cells provide the possibility of optimizing the devices performance. The two different active layers of sub-cells have non-overlapping light absorption scales, which make the light utilized more adequately. Therefore, the tandem architecture of devices can extend the light absorption within the solar spectrum and effectively reduce energy loss resulting from thermalization loss and transmission loss. According to Shockley and Queisser's calculation, the limitation of the PCE of a tandem solar cell is 42%, which is higher than 33.8% of a single-junction solar cell. In organic photovoltaics field, the developments of the tandem solar cells benefit from the optimization of active layers, interconnecting layers and construction methods. These achievements have resulted in higher PCEs and the devices approaching practical application. At present, the highest PCE of tandem organic solar cell is 17.3% obtained by Chen's group in 2018, but it is still far from the PCE limitation. According to Kirchhoff's law, the open-circuit voltage (V_OC) in series tandem cells is theoretically equal to the sum of the V_OCs of sub-cells, and the short-circuit current (J_SC) in parallel cells is equal to the sum of the J_SCs of sub-cells. Hence, the series tandem solar cells still face with the challenge of the unmatched J_SCs and the complexed processing methods. Here, this review mainly focuses on the materials used in tandem solar cells, the structure of the interconnecting layers, the processing methods, the measurement methods and the applications. The critical achievements on tandem organic solar cells in recent years and the progress of larger scale, flexible tandem devices are summarized in this review. It also presents the outlooks of the high performance tandem solar cells based on the material and structure requirements.

Optically pure pyrrolidine ring systems are core structural motifs found in a range of bioactive compounds, natural products, pharmaceuticals and catalysts. The synthesis of optically pure pyrrolidine ring systems is no longer mysterious as a great number of studies concerning the catalytic asymmetric 1,3-dipolar cycloaddition of iminoesters have been reported. Overall, the transition-metal-catalyzed asymmetric 1,3-dipolar cycloaddition of iminoesters with electron-deficient alkenes is one of the most powerful and straightforward synthetic tools for the optically pure pyrrolidines. However, high diastereo-and enantioselectivities are requested simultaneously during the synthesis of chiral substituted pyrrolidine and it still remains a big challenge to develop an efficient way to achieve both of them. Recently, we developed a novel chiral sulfinamide mono-phosphine (Ming-Phos) which performed well in copper-catalyzed intermolecular cycloaddition of iminoesters with β-trifluoromethyl β,β-disubstituted enones or α-trifluoromethyl α,β-unsaturated esters. Encouraged by the satisfying results, herein we report the Ming-Phos/Cu-catalyzed asymmetric intermolecular[3+2] cycloaddition of azomethine ylides with nitroalkenes. To our delight, a new Ming-Phos M3 bearing a trifluoromethyl showed good performance in this type of inter-molecular cycloaddition with high diastereo-and enantioselectivities (up to 13:1 dr, 98% ee and 95% yield). High efficiency, high diastereo-and enantioselectivity, a novel ligand, an inexpensive copper catalyst, and good functional group tolerance make it worth to be considered as an efficient, reliable and atom-economic strategy for the synthesis of optically pyrrolidines. The general procedure is as following:the solution of M3 (5.5 mol%) and Cu(CH₃CN)₄BF₄ (5 mol%) in methyl tert-butyl ether (MTBE, 6 mL) was stirred at room temperature for 2 h. After the reaction temperature was dropped to -30℃, azomethine ylides 2 (0.6 mmol), Cs₂CO₃ (0.15 mmol) and nitroalkene 1 (0.3 mmol) were added sequentially. After the nitroalkene 1 was consumed completely, the solvent was removed under reduced pressure. The crude product was analyzed with ¹H NMR to determine the diastereomeric ratio. Then the crude product was then purified by flash column chromatography on silica gel to afford the desired product.

Cholesteric liquid crystals (CLCs) are a kind of intriguing soft photonic crystal materials, in which the orientation of LC molecules varies in a helical fashion, and selectively reflect light, known as structural color, according to Bragg's law. Moreover, the structural color determined by the pitch length of the helices in CLCs can be tuned owing to the dynamic control of inherent self-organized helical superstructures in response to external stimuli. Currently, light-driven CLCs have attracted extensive interest because light, compared to other stimuli, has unique advantages of remote, temporal, local and spatial manipulation. Such elegant systems are generally formulated by doping light-driven chiral switches, mainly consisting of chiral centers and photoswitches, into a nematic LC host. The chiral centers are able to twist the nematic LC host into helical superstructures, which is represented by helical twisting power (HTP). The photoswitches undergo configurational changes upon photoisomerization, leading to the variation in HTP and the pitch length of the helices, and consequently tune the structural color of the CLCs. These light-driven CLCs provide opportunities for various photonic applications such as tunable filters, sensors, tunable optical lasers, and optically addressed displays. In this review, we summarize diverse light-driven CLC systems according to the type of the photoswitch in doped chiral switches. Azobenzene-and motor-based chiral switches usually have high HTP and large variation in HTP, which enables the tuning range of the resultant CLC to cover visible spectrum. Besides, chiral switches based on dithienylethenes have also been synthesized and utilized to tune the reflection of the CLC across red, green and blue colors that remain unchanged in darkness even after one week because of the excellent thermal stability of dithienylethenes. Chiral switches based on dicyanoethene are used to construct an optically tunable reflective-photoluminescent CLC system. Importantly, the design of the light-driven chiral switches is analyzed in detail to reveal the structure-property correlation. Potential and demonstrated practical applications of light-driven CLCs are discussed, and forecast of existing challenges and opportunities in CLC systems are concluded.

Single-molecule magnets (SMMs), exhibiting magnetic bistability and slow magnetization relaxation, have fascinated scientific community for their promising applications in data storage and information processing. Great development has been achieved in lanthanide-based SMMs due to the unquenched orbital momentum and strong anisotropy of lanthanide ions. According to the crystal-field theory, the magnetic anisotropy of lanthanide ions arises from crystal-field splitting. Appropriate arrangement of coordination environment of lanthanide ion (including the local symmetry as well as the charge distribution) is key to design high-performance SMMs. However, it still remains a huge challenge to generate lanthanide-containing compounds with certain coordination environment. Taking advantage of metallacrown (MC) approach, herein a series of 3d-4f complexes {TbNi₅X₂} (X=F, Cl, Br) were successfully isolated via solvothermal reactions. To obtain these complexes, a mixture of stoichiometric metal salt and quinaldichdroxamic acid with excess of pyridine derivative was dissolved in methanol and then heated at 75℃ for 2 d. X-ray single-crystal diffraction analysis indicated that the Tb(III) site equatorially coordinates with[15-MC_Ni(II)-5], whilst is axially capped by halide ions. As a result, the lanthanide ion possesses high axiality with a pentagonal bipyramid geometry (D_5h). Alternative current magnetic susceptibility data revealed that the electrostatic interactions between f-electrons and ligand electrons play an important role in modulating the magnetic relaxation dynamics. Maximizing the axial charge density in {TbNi₅F₂} where the[F-Ln-F]⁺ moiety is firstly reported in lanthanide chemistry, the oblate Tb(III) is placed in a judicious crystal field. The out-of-phase signal of {TbNi₅F₂} shows obvious temperature and frequency dependence under 1 kOe applied dc field. Additionally, the slow magnetization relaxation of {TbNi₅F₂} can be fitted by the power law or Arrhenius plot with reversal barrier of 19.0 K. By lowering the electrostatic interactions of axial ligation, the out-of-phase signal significantly weakens in {TbNi₅Cl₂} and even vanishes in {TbNi₅Br₂}. The decline of magnetic anisotropy in {TbNi₅Cl₂} and {TbNi₅Br₂} accelerates the fast quantum tunneling of magnetization. The results demonstrate for the first time that the Off/Part/On slow magnetization relaxation can be modulated via the improvement of electronegativity of axial ligands.

The electrolyte, which is an important medium of ion conduction for secondary batteries, plays a crucial role in improving the cycling performance and safety performance of secondary batteries. Localized high-concentration electrolytes, which are formed by adding "diluent" into high-concentration electrolyte, not only reserve the outstanding properties of high-concentration electrolytes but also possess low viscosity, excellent wettability and low cost, promising broad application prospect. Localized high-concentration electrolytes have already played a part in flame-retardant lithium battery, high-voltage lithium battery, low-temperature lithium battery, lithium sulfur battery and sodium battery. Herein, this paper mainly reviews the types and preparation of localized high-concentration electrolytes and their functional mechanism and research status in various secondary batteries. We discuss the challenges and future development of localized high-concentration electrolytes and have the outlook at the end of the paper.

Due to the lower redox potential comparing with guanine, it is the 8-azaguanine (8-AG) as the hole trap to form 8-azaguanine radical cation (8-AG^·+) after one-electron oxidation of DNA containing 8-azaguanine. In generally, the 8-AG^·+ may suffer from deprotonation to generate 8-AG(-H)·. In this text, we were stimulated to investigate the deprotonation reaction of 8-AG^·+ generating by one-electron oxidation at M06-2X/6-31+G(d) level with explicit water molecules and polarized continuum model (PCM) to simulate the solvent effect. By building deprotonation model with different number of explicit water molecules, we found that these four water molecules locating around N(1)-H, O(6), N(2)-H of 8-AG^·+ as well as the one locating in the second water shell which was hydrogen-bonding with the water around O(6) were necessary. If the water in the second water shell was not included, the imino proton (N(1)-H) would not transfer into the bulk water. In parallel, the N(1)-H would transfer to the O(6) of 8-AG^·+ by intramolecular proton transfer. If the water molecule locating around N(2)-H was removed, the 8-AG^·+ deprotonation would continue but the energy barrier would be lowered from 24.8 kJ/mol to 16.3 kJ/mol. In addition, the site of the water molecule in the second water shell was also studied. If putting the water in the second water shell around N(2)-H of 8-AG^·+, the proton would be stabilized between the N(1) of 8-AG^·+ and the oxygen of water molecule around N(1)-H meaning the proton would not be transferred into bulk water. Further, in order to test the influence of water number on 8-AG^·+ deprotonation, the fifth water molecule, which is hydrogen-bonding with the water molecule around N(2)-H and another N(2)-H, was added. The potential energy surface with 5H₂O revealed that it is almost no effect on the deprotonation pathway and energy barrier (25.5 kJ/mol). Lastly, so as to obtain the exact energy barrier of 8-AG^·+ deprotonation, the deprotonation model with more explicit water molecules (9H₂O) was proposed, where the additional water molecules were placed around N(2)-H, N(3), O(6), N(7) and N(8). From the potential energy surface, the deprotonation energy barrier of 8-AG^·+ was confirmed to be 19.5 kJ/mol. These theoretical results provide valuable dynamics information and mechanistic insights for further understanding the properties of nucleic acid base analogues and one-electron oxidation of DNA.

Fluorescence imaging plays an important role in the diagnosis and treatment of major diseases by virtue of its high sensitivity, strong specificity and excellent spatio-temporal resolution. However, traditional near-infrared-I (NIR-I, 700~900 nm) fluorescence imaging often encounters multiple concerns such as poor tissue penetration, which limits its clinical application. In recent years, near-infrared-II (NIR-II, 1000~1700 nm) fluorescence imaging has been proven to provide better imaging qualities, higher signal-to-noise ratio and deeper tissue penetration than those observed in the NIR-I window due to the diminished photon scattering and tissue auto-fluorescence. Among NIR-II fluorescent probes, organic small molecules are becoming research hotspots in this field due to their advantages of low toxicity, simple structure and fast metabolism. This review describes the recent progress in the design of organic small molecule NIR-II probes and the strategies for improving the fluorescence quantum yield. The application of small molecule NIR-II probes in activatable imaging, multimode imaging and theranostics are evaluated systematically. Current challenges and future perspectives in this emerging field are also prospected.

As important chemical raw materials and energy source, C₄~C₆ hydrocarbons are mainly used to produce polymer rubber, plastics and high-quality gasoline, which requires high purity of the raw materials. For example, the purity requirement in 1,3-butadiene polymerization reactor is higher than 99.5%. When producing butyl rubber, tert-butylamine, pivalic acid, etc., the purity of isobutylene should surpass 99%. In the traditional petrochemical industry, C₄~C₆ hydrocarbons are mostly separated and purified through distillation, yet suffering from large energy consumption, high equipment cost and poor economic benefits. Adsorption separation with solid adsorbents can not only reduce energy cost and environmental footprints, but also improve separation efficiency. Metal-organic frameworks (MOFs) are a class of crystalline porous materials assembled from metal ions or clusters and organic linkers. Compared with zeolite, activated carbon and silica gel, MOFs feature high porosity, well-defined open channels, rich functional groups and diverse structures, showing great potentials in gas storage and separation, sensing, catalysis, photoelectric devices, drug release and delivery. Up to now, there have been many reports on separation and purification of C₄~C₆ hydrocarbons using MOFs by different mechanisms. Specifically, highly selective separation can be achieved by precisely adjusting the size and shape of the MOF channels to match the size of the target molecule. Besides, selecting MOFs with specific functional groups, open metal sites or flexible skeletons to regulate the interactions between the gas molecules and backbone, can also achieve efficient separation. This review introduced the importance of C₄~C₆ hydrocarbons separation and summarized the current research progress of using MOFs to separate and purify C₄~C₆ hydrocarbons. In addition, we also summed up the challenges of using MOFs as industrial adsorbents and pointed out the possible research directions in the future, which may provide ideas for designing new MOFs with high performance for crucial separation processes.

With the rapid development of electric cars and energy storage power stations, there is an increasing demand for lithium ion batteries with high energy density. Li- and Mn-rich (LMR) cathode materials with large specific capacity (>250 mAh·g^-1) are supposed to accomplish lithium ion batteries with high energy density (>350 Wh·kg^-1). The high capacity performance of LMR cathode materials are resulted from the lattice oxygen redox reaction induced by the electrochemical activation of the Li₂MnO₃ phase. However, the activation of the Li₂MnO₃ phase and oxygen redox reaction lead to lattice oxygen release and structure transformation, which cause some serious problems such as low initial columbic efficiency, poor rate capability, voltage and capacity degradation after subsequent cycles. The oxygen release and structure transformation always start from the surface, indicating that the surface stability is significant to LMR cathode materials. In this paper, surface modifications such as surface coating, surface doping and surface chemical treatment are reviewed and the mechanism of three surface modification methods for LMR cathode materials are discussed in further. Surface coating is one of the most widely surface modification methods, which can suppress the electrode/electrolyte side reaction and reduce the transition metal dissolution. The effect of surface coating on improving electrochemical performance of LMR cathode materials is always determined by the characteristic of coating layer materials including non-active coating layer, electrochemical active coating layer, Li⁺ conductive coating layer and electronic conductive coating layer. Surface doping has shown to be an effective method in suppressing oxygen release and structural transformation. Surface chemical treatment has resulted in reducing irreversible capacity loss by activating Li₂MnO₃ phase. On this basis, surface integrated strategies combined several surface modified methods are introduced and discussed in recent years. The surface intergrated strategies not only enhance the structural stability and suppress electrode/electrolyte surface-interface reaction, but also have an effective role on mitigating structure transformation and lattice oxygen release. Finally, we wish that our review would provide research directions for surface modified strategies of LMR cathode materials in future.

Metal-organic frameworks (MOFs), featuring the ultrahigh surface area, high porosity, tunable geometrical and chemical properties, show potential applications in gas adsorption/separation, heterogenous catalysis, etc. As the ubiquity of water vapor in the ambient environment and industrial gas streams, it is necessary to study on interaction mechanism between MOFs and water molecules and develop highly water-stable MOFs with desirable water adsorption/desorption behaviors. It not only has the scientific significance, but also great importance in promoting the practical applications of MOFs. Given the tailorable abilities of pore size, pore volume, cavity hydrophilicity and water stability, MOFs provide unprecedented advantages to explore the well-defined porous sorbents in molecular level, which facilitates the realization of reversible water vapor uptake and release at expected relative pressure and temperature together with high working capacity. For now, a wide range of hydrolytically stable MOFs including high-valence metal (e.g. Cr³⁺, Al³⁺, Zr⁴⁺, Ti⁴⁺) based frameworks have emerged as the advanced and promising porous sorbents for energy efficient applications, by utilizing water as eco-friendly adsorbate media and renewable heat. This review focuses on the following aspects:(1) the degradation mechanism of MOFs in liquid phase of water and the design concepts of hydrolytically stable MOFs by modulating their coordination bond based on the Pearson' hard/soft acid/base principle; (2) the physical or chemical water ad/desorption properties of MOFs; (3) the classification of numerous MOFs sorbents and conventional desiccants based on their hydrophilicity, which is approximately reflected by the relative humidity (RH) value of the inflection points (the RH where the steep uptake starts) in isotherms; (4) a variety of water adsorption-based applications of MOFs such as industrial gas dehydration, drinking water harvesting in the desert area, adsorption-based heat pump and indoor humidity regulation. Finally, the research priorities and development outlook are summarized and the future challenge with respect to water adsorption-based applications for the next-generation MOFs are outlined.

The increasing shortage of freshwater resources and water pollution are important challenges facing the world, and vigorous development of seawater desalination and water treatment technologies is an effective way to alleviate this problem. In recent years, low energy consumption and green membrane-separation technology has been widely used in the fields of seawater desalination and water treatment. Covalent organic framework (COF) membranes are potential high-performance membrane separation materials due to their adjustable pore size and chemical environment. In this paper, the research progress of COF-membranes synthesis methodology is introduced in detail, the research of COF membranes in seawater desalination and water treatment is summarized, and the challenges and perspectives of COF membranes for seawater desalination and treatment are elaborated.

Anderson type heteropoly acids, also known as Anderson type polyoxometalates, are a kind of important structures in polyoxometalates. Their general structural formula can be expressed as [XM₆O₂₄]^n－, in which the core heteroatom X can almost be replaced by almost any metal or nonmetal element in the periodic table. Due to unique structure easy to be modified with organic ligands and designability, as well as their potential applications in materials, catalysis and medicines, Anderson type heteropoly acids have been widely concerned by researchers. In recent years, the application of Anderson type heteropoly acids in organic synthesis has gradually shown great significance for the study of green catalytic process. In this paper, the catalytic application of Anderson type heteropoly acids in organic synthesis has been reviewed and summarized according to the structure classification of Anderson type polyoxometalates. This will be helpful for the researchers to further study the catalytic application of Anderson heteropoly acids and provides new ideas for the research of green catalysis.

Carbon dioxide (CO₂) is an abundant, inexpensive, non-toxic and renewable C1 resource, and it is also a kind of green monomer. The polymerizations based on CO₂ have been one of the hot research topics. The copolymerization of CO₂ and epoxide monomers was widely studied in the past few years and has been industrialized. Some new polymerizations based on CO₂ have also been reported recently. There are two ways to produce polymeric materials from CO₂. One is converting CO₂ into monomers for further ring opening or step growth polymerizations, such as lactone, cyclic carbonates, furan-2,5-dicarboxylic acid. Another is directly using CO₂ as a monomer for the copolymerization with other monomers to generate polymers. They are both significant for developing new polymerizations based on CO₂ and expanding CO₂-based polymeric materials. The advances in converting CO₂ into polymeric materials during the past few years are summarized in this review and the perspective in this area is discussed.

Two thermally activated delayed fluorescence (TADF) materials TBP-DmCz and TBP-TmCz were successfully synthesized using 1,3,5-tribenzoylbenzene (TBP) as electron-acceptor, 1,8-dimethylcarbazole (DmCz) and 1,3,6,8-tetra-methylcarbazole (TmCz) as electron-donor, respectively. Thermal gravimetric analysis show that the thermal decomposition temperatures (T_d) are 479℃ for TBP-DmCz and 484℃ for TBP-TmCz and no glass transition was found for both materials during the differential scanning calorimetry investigations. The highest occupied molecular orbitals (HOMO) are confined on the carbazole unit, while the lowest unoccupied molecular orbitals (LUMO) are located on the 1,3,5-tribenzoylbenzene unit, and there is almost no overlap between HOMO and LUMO, which is the typical molecular orbital character of TADF materials. Meanwhile, TBP-DmCz and TBP-TmCz possess degenerated HOMO and LUMO, which would promote the radiative transitions as the transitions could take place from all degenerated LUMOs to HOMOs. The HOMO level of TBP-TmCz is obviously higher than that of TBP-DmCz due to increasing the number of methyl groups at the electron-donor carbazole, and the LUMO levels of TBP-DmCz and TBP-TmCz only show a small difference because these materials have the same electron-acceptor 1,3,5-tribenzoylbenzene. In toluene solution, these materials have very similar absorption spectra and exhibit absorption bands assigned to intramolecular charge-transfer transition. The spectral peaks are located at 488 nm for TBP-DmCz and 502 nm for TBP-TmCz, respectively, in toluene solution at room temperature. According to the fluorescence and phosphorescence spectra of these materials in 1,3-bis(N-carbazolyl)benzene (mCP) film at 77 K, the energy gaps between the lowest singlet and triplet (ΔE_ST) of TBP-DmCz and TBP-TmCz are calculated to be 0.05 and 0.01 eV, respectively. The fluorescence decay behaviors at different temperatures (100, 200 and 300 K) proved that emissions of TBP-DmCz and TBP-TmCz contain TADF component. The electroluminescence devices with TBP-DmCz and TBP-TmCz as the emitters show high efficiency and low efficiency roll-off. The maximum external quantum efficiencies of devices based on TBP-DmCz and TBP-TmCz are 13.6% and 18.3%, respectively.

Metal organic frameworks (MOFs) have unique advantages in adsorption and preconcentration of heavy metal ions due to their structure and composition characteristics, which make them show great potential in optical sensing of heavy metal ions. However, their applications in the field of electrochemical sensing is greatly limited because of their poor conductivity. In this work, a functionalized MOF composite, thermally reduced graphene oxide-Au nanoparticles-zeolitic imidazolate skeleton material (RGO-Au-ZIF-8), was fabricated. It exhibits much improved electrochemical properties compared with the pristine MOF. A novel electrochemical sensing platform was constructed based on it, and simultaneous detection of lead ions (Pb²⁺) and copper ions (Cu²⁺) in aqueous solution was realized. Specifically, the Au-ZIF-8 was prepared by adding polyvinylpyrrolidone (PVP)-stabilized Au nanoparticles (AuNPs) to the reaction solution of ZIF-8. The modification of AuNPs effectively improved the conductivity of the material. After compounding with RGO, the RGO-Au-ZIF-8 composite was prepared. The RGO was used as scaffold for the Au-ZIF-8 in the composite to increase the effective surface area of electrode and improve conductivity. The morphology and structure of the prepared materials were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and UV-visible absorption spectroscopy (UV-Vis). The electrochemical properties of the modified electrodes were characterized by various electrochemical techniques. The experimental parameters, such as pH value of working solution, accumulation potential, accumulation time and composition ratio of Au-ZIF-8 to RGO were optimized. Under the optimized conditions, simultaneous and sensitive detection of Pb²⁺ and Cu²⁺ on the prepared electrochemical sensor was realized with the detection limits of 2.6×10^-9 and 7.8×10^-9 mol·L^-1 for Pb²⁺ and Cu²⁺, respectively (S/N=3). The interference test showed that the electrochemical sensor has good selectivity for the detection of Pb²⁺ and Cu²⁺, and further electrochemical studies revealed that the designed sensor has excellent reproducibility and good stability. The result of recovery test indicated that the prepared electrochemical sensor has great potential in Pb²⁺ and Cu²⁺ detection in real water samples. This work provides a new platform for simultaneous, rapid and sensitive detection of heavy metal ions, and greatly expands the electrochemical applications of MOF materials.

Thermally activated delayed fluorescence (TADF) molecules have great potential in developing organic light-emitting diodes (OLEDs) because of their efficient emission and low price. Compared to pure-molecules, exciplex systems are drawing much attention since they can realize small singlet-triplet energy splitting (ΔE_ST) more easily for TADF. However, the species and molecular design systems of electron-acceptors for exciplex-TADF are still limited even though some acceptors have been reported. In addition, the relationship between TADF properties and the structures of acceptors requires further investigations. Herein, we report the design and synthesis of two novel spiro[fluorine-9,9'-xanthene]-based acceptors (CNSFDBX and DCNSFDBX) for achieving exciplex-emissions by using tris(4-carbazoyl-9-ylphenyl)amine (TCTA) as a donor. The photoluminescence measurements suggest that both of the doping-systems (TCTA:CNSFDBX and TCTA:DCNSFDBX) possess exciplex emissions. Whereas, it is observed that the TCTA:DCNSFDBX system displays higher photoluminescence quantum yield and electroluminescence efficiency than TCTA:CNSFDBX. For better explaining this phenomenon, we perform low-temperature fluorescence and phosphorescence spectra investigations. The experimental results show that the TCTA:DCNSFDBX system exhibits smaller ΔE_ST values (0.12 eV) than TCTA:CNSFDBX (0.46 eV). This results indicate that the reverse intersystem crossing from non-radiative triplet states (T₁) to radiative singlet states (S₁) and TADF processes can be realized more easily in the TCTA:DCNSFDBX system. Moreover, the electrochemical measurements and theoretical calculations suggest that the lowest unoccupied molecular orbital (LUMO) level of DCNSFDBX (-2.86 eV) is lower than that of CNSFDBX (-2.47 eV). This situation implies that DCNSFDBX possesses stronger electron-accepting ability than CNSFDBX with the help of dicyano-substitution. Furthermore, the TCTA:DCNSFDBX system displays larger driving force (0.39 eV) than TCTA:CNSFDBX (0.22 eV) in their exciplex-formation processes, suggesting the exciplex-emission (TCTA:DCNSFDBX) can be achieved more easily. Therefore, the higher exciplex-emission efficiencies of the TCTA:DCNSFDBX system are attributed to the stronger electron-acceptability of DCNSFDBX through dicyano- substitution and larger driving force in its exciplex emission process. This work provides a route to further development of new electron-acceptors for exciplex-TADF.

Highly sensitive and accurate analysis of significant biomarkers such as alkaline phosphatase (ALP) is essential for early detection and treatment of diseases. In this work, a fluorescence/UV-vis dual-mode sensing platform was constructed for amplified detection of ALP and pyrophosphate ion (PPi) based on mimic enzyme-natural enzyme cascade reactions. Cu-Based metal-organic frameworks HKUST-1 which possesses of oxidase-like activity and can effectively catalyze the oxidation of indicator o-phenylenediamine (OPD) by the surface-active sites were prepared. The oxidation products of OPD exhibit strong UV-vis absorption and fluorescent signals at 416 and 568 nm, respectively. After adding PPi, the catalytic activity of HKUST-1 was selectively inhibited due to the combination of PPi with Cu²⁺ on the surface of HKUST-1, that resulted in fluorescence and UV-vis signal reducing. Once ALP was introduced into the system, PPi can be specifically hydrolyzed into phosphate ions (Pi), and the oxidase-like activity of HKUST-1 recovered. Thus, the fluorescent and UV-vis signals were regenerated by an ALP-triggered mimic enzyme-natural enzyme cascade reaction. On account of the inhibition of oxidase-like activity of HKUST-1 by PPi and the recovery by ALP, an ultrasensitive dual-mode sensing platform of biomarkers based on mimic enzyme-natural enzyme cascade reactions has been developed. Under optimal conditions, the linear range of ALP by fluorescence/UV-vis detection is 0.02~3.5 and 0.04~3.5 nmol·L^-1, and the detection limit of fluorescence and UV-vis assay is as low as 0.0078 and 0.039 nmol·L^-1, respectively. As far as we know, it is the first time that the mimic enzyme-natural enzyme cascade reaction is applied to dual-mode bioanalysis. Due to the enzyme cascade amplification and dual-mode signal output, this developed strategy has the advantages of high sensitivity, low detection limit, high accuracy and reliability, and can realize ultrasensitive analysis of ALP in human serum samples, which shows great potential for clinical diagnosis.

In this work, the separation performance of methane/ethane/propane (C₁, C₂ and C₃) mixture in the 137953 hypothetical metal-organic frameworks (MOFs) is calculated by high throughput computational screening and multiple machine learning (ML) algorithms. First, to avoid the competitive adsorption of water vapor, 31399 hydrophobic MOFs (hMOFs) were screened out. Then, grand canonical Monte Carlo (GCMC) simulations were employed to calculate the adsorption behavior of a mixture with a mole ratio of C₁:C₂:C₃=7:2:1 in these hMOFs, respectively. Second, the relationships among six MOF structures/energy descriptors (the largest cavity diameter (LCD), void fraction (f), volumetric surface area (VSA), Henry coefficient (K), heat of adsorption (Q_st), density of MOF (ρ)) and three performance indicators of MOFs (selectivities (S), adsorption capacities (N) of C₁, C₂, C₃ and their trade-offs (TSN)) were established. The LCDs were calculated by Zeo++software, and VSAs were calculated using RASPA software using He and N₂ as probes, respectively, and Q_st and K were calculated in an infinite dilution of each gas molecule in an infinite dilution state using NVT-MC method in RASPA software. Then, we found that there existed the "second peaks" of N and S in part of structure-property relationships, and all the optimal MOFs located in the range of second peaks, especially for the separation of C₁ or C₂. Third, the above-mentioned six MOF descriptors and three MOF performance indicators were trained, tested and predicted by four ML algorithms, including decision tree, random forest (RF), support vector machine and Back Propagation neural network. Although the predictive effect for the selectivity was very low, the introduction of TSN can significantly improve the accuracy of ML prediction, especially for RF algorithm (R=0.99). Therefore, the RF was used to quantitatively analyze the relative importance of each MOF descriptor, and found that three descriptors (K, LCD and ρ) possessed the highest importance for the separation of C₁ and C₂, and three other descriptors (K, Q_st and ρ) for the separation of C₃. Moreover, three simple and clear paths of optimal MOFs for C₁, C₂ and C₃ adsorption were designed by the decision tree model with the descriptors. Based on those paths, there were 96%, 85%, 95% probability that we can search for high-performance MOFs, respectively. Finally, the best 18 MOFs were identified for different separation applications of C₁, C₂ and C₃. This study reveals the second peaks and key MOF descriptors governing the adsorption of light alkane, develops quantitative structure-property relationships by ML, and identifies the best adsorbents from a large collection of MOFs for the separation of C₁, C₂ and C₃ from natural gas.

The partitioning of volatile substances in atmospheric particulates is a hot topic in atmospheric science. Ammonium nitrate (NH₄NO₃) is an important inorganic component in atmospheric aerosols, which is a salt with relatively high vapor pressure. Particles containing NH₄NO₃ are equilibrium with gaseous NH₃ and HNO₃ and the partitioning between particle and gas is a strong function of temperature and relative humidity. Atmospheric aerosols have both natural and anthropogenic sources and consist of both organic and inorganic components, and many of them will likely form in semisolid, glassy, and high viscous state in the atmosphere, which show nonequilibrium kinetic characteristics at low relative humidity conditions. In this research, in order to understand the volatility of ammonium nitrate in ultra-viscous aerosol droplets, optical tweezers coupled with cavity-enhanced Raman spectroscopy were employed to observe the volatility of ammonium nitrate in the mixture of NH₄NO₃/MgSO₄ and NH₄NO₃/sucrose droplets. Optical tweezers-stimulated Raman spectroscopy, compared with other suspension techniques, can not only suspend droplets, but also obtain the chemical composition, structure of droplets and other information according to the conventional Raman scattering spectra of droplets. The radius and refractive index of droplets can be calculated according to stimulated Raman-Mie scattering resonance. The advantages of optical tweezers stimulated Raman spectroscopy are that particle radius can be accurately measured, chemical composition, phase and shape can be controlled, and long-term observation can be realized. Here, the radii and refractive indexes of the levitated droplets were determined in real time using the wavelength positions of stimulated Raman spectra, and the effective vapor pressures of ammonium nitrate at different relative humidity (RH) were obtained according to Maxwell equation. For the droplets with ammonium nitrate/sucrose molar ratio of 1:1, the effective vapor pressure of ammonium nitrate decreased with the decrease of RH. When the RH decreased from 70% to 20%, the effective vapor pressure of ammonium nitrate decreased from (3.577±0.82)×10^-5 to (6.55±1.36)×10^-6 Pa, compared to the vapor pressure of pure ammonium nitrate (1.67±0.24)×10^-3 to (6.64±0.3)×10^-3 Pa, the evaporation of ammonium nitrate in the mixed droplet was suppressed by sucrose, especially at low RH. For the mixed droplets with ammonium nitrate/magnesium sulfate molar ratio of 1:1, a similar phenomenon was observed. When the RH decreased from 70% to 40%, the effective vapor pressure of ammonium nitrate decreased from (4.38±0.21)×10^-3 to (8.13±2.34)×10^-5 Pa. The results showed that the effective saturated vapor pressures of ammonium nitrate in ultra-viscous droplets at low humidity were 1~3 orders lower than those of pure ammonium nitrate. Obviously, the volatilization of ammonium nitrate in droplets was inhibited at low relative humidity.

Nitroxyl (HNO), produced by nitric oxide (NO) with one-electron reduction and protonation, has recently received substantial interest due to its important roles in various biological functions and pharmacological activities. Research indicates that HNO also has many potential pharmacological applications for different diseases. Therefore, the development of a reliable method for HNO assay in biosystems is highly desired. Ratiometric fluorescent probes show significant advantages over traditional “turn-on” ones, because simultaneous measurement of two emission signals can provide a built-in correction and thus minimize the inaccurate fluorescence signal readouts. As far as we know, there is no ratiometric fluorescent probe for HNO detection based on upconversion nanoparticles (UCNPs). Herein, a ratiometric nanoprobe for HNO assay was constructed based on the luminescence resonance energy transfer (LRET) principle by using UCNPs with a core-shell structure (NaYbF₄:30%Gd@NaYF₄:2%Yb:1%Tm) as the energy donor and an organic dye Fl-TP as the potential energy acceptor. The oleate-coated UCNPs (OA-UCNPs) and Fl-TP were assembled through hydrophobic interaction to construct the upconversion nanoprobe (termed as Fl-TP-UCNPs). Because of the ring-closed form, Fl-TP displayed weak absorption and was non-fluorescent, which blocked the LRET process. After reaction with HNO, the triphenylphosphine moiety left and released Fl-HNO with the fluorescent ring-open form. Fl-HNO showed strong absorption in the range of 400～500 nm, which completely overlapped with the blue luminescence of UCNPs and triggered the LRET process between UCNPs and Fl-HNO. Thus, the luminescence from UCNPs around 480 nm decreased and the emission from Fl-HNO around 525 nm increased with a [HNO]-dependent manner. The ratiometric luminescence intensity F_{525 nm}/F_{480 nm} showed a good linear relationship (R²＝0.9914) to the logarithm of AS (Angeli’s salt, a generally used HNO donor) concentration in the range of 3～100 μmol·L^－1 and the limit of detection was 23.4 nmol·L^－1. The excellent sensitivity, stability, selectivity and low cytotoxicity endow Fl-TP-UCNPs with the superior capability for HNO assay in vitro and in vivo. We found that Fl-TP-UCNPs probe is appropriate for monitoring HNO in living cells as well as imaging HNO in liver tissues. This probe may be a powerful tool for HNO assay in various physiological processes.