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.

Transition metal-catalyzed coupling reactions are powerful synthetic methods for the C-C bond formation. Many coupling reactions such as Heck reaction, Negishi coupling, and Suzuki coupling have been widely applied in the syntheses of pharmaceuticals, functional materials and fine chemicals. In those coupling reactions, a C(sp²)-C(sp²) bond is formed in high efficiency and selectivity. However, in contrast to the C(sp²)-C(sp²) couplings, the C(sp³)-C(sp³) couplings are more difficult and develop late. Because the C(sp³)-C(sp³) bonds are ubiquitous in organic compound, the C(sp³)-C(sp³) bond formation is the central task of research in organic chemistry. In the past two decades, a great effort has been devoted to the development of cross-coupling reactions between alkyls to construct C(sp³)-C(sp³) bonds and impressive progress has been achieved. Among the transition metal catalysts that have been used in the construction of C(sp³)-C(sp³) bonds, nickel was found to be a preferable one, exhibiting unique activity and selectivity. Nickel catalysts promote the activation of alkyl electrophiles via radical catalytic cycles and inhibit and/or manipulate β-H elimination reactions. Nickel has several variable valence states and can flexibly participate in tandem reactions and reductive cross-coupling reactions. All these characteristic natures contribute to the success of nickel catalysts in the construction of C(sp³)-C(sp³) bonds. In this review, we will describe the advances on the nickel-catalyzed C(sp³)-C(sp³) bond-forming reactions. The main contents of this review include:the cross-coupling of alkyl electrophiles with organometallic reagents; the coupling involving a C(sp³)-H bond activation in the presence of directing group; the coupling co-catalyzed by nickel and photocatalyst; the reductive coupling of two alkyl electrophiles; and the additions of nucleophiles or electrophiles to alkenes such as hydroalkylation and difunctionalization of alkenes. The review will focus on the latest developments of nickel-catalyzed alkyl coupling reactions in the past two decades. The mechanisms of each reaction are discussed in detail for understanding the reactions.

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.

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.

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.

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.

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.

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.

Room-temperature phosphorescence (RTP) can not only intuitively reflect the excited state transition process of the phosphorescent luminescence, but also has wide potential applications in optoelectronics, sensing, bioimaging and security devices. Consequently, more and more attention and interests on RTP materials have been attracted, which turned it to be one of hot topics in luminescence materials, especially, organic luminescence materials in recent years. The halogen bonds and hydrogen bonds between the molecules can fix the phosphor to suppress non-radiative transitions. A twisted donor-acceptor skeleton can promot efficient thermally activated delayed fluorescence (TADF) and also benefit to the RTP. Moreover, circularly polarized room-temperature phosphorescence (CP-RTP) also remains a daunting challenge to implant circularly polarized luminescence (CPL) in metal-free RTP materials. This review summarizes recent research progress on RTP of small organic molecules, mainly focusing on RTP materials based on hydrogen bonds, RTP materials containing halogens, RTP materials based on D-A structures and RTP materials with CPL properties.

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.

Hydrogen-bonded organic frameworks (HOFs), usually self-assembled by organic or metal-organic building blocks via intermolecular H-bonding interactions, have become a unique type of crystalline porous material. Although the weak and flexible nature of hydrogen bonds makes most HOFs fragile, the high stability and permanent porosity could be realized by the judicious selection of rigid building blocks with special spatial configuration as well as the introduction of framework interpenetration and/or other intermolecular interactions like π-π stacking and electrostatic interactions, etc. Compared with other crystalline porous materials like metal-organic frameworks (MOFs) and covalent-organic frameworks (COFs), HOFs feature mild preparation condition, high crystallinity, permissible solution processability, easy healing and regeneration, etc. These distinguishing merits make HOFs capable to be used as unique multifunctional porous materials. Herein, we first review the basic rules to design and synthesize stable and porous HOFs, and then systematically summarize the representative supramolecular synthons and backbones that have been used to build stable and porous HOFs. Emphasis is put on the potential applications of HOFs in gas adsorption and separation, proton conduction, heterogeneous catalysis, luminescence and sensing, biological applications, enantiomeric resolution and aromatic compounds separation, pollutants removal, and structure determination, etc.

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.

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.

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.

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.

Aqueous zinc ion batteries (AZIBs) as an emerging battery energy storage technology have attracted widespread attention and developed rapidly in recent years due to the merits of high safety, low price, high energy density, environmental friendliness, easy manufacturing, etc., showing good application value and prospect in large-scale energy storage and other fields. Embarking from the current scientific issues existed in AZIBs, we review the important progress in cathode and anode materials and electrolyte used in AZIBs in this article. Firstly, the characteristics of multiple cathode materials that developed and their electrochemical reaction mechanism are analyzed and summarized. Afterward, the challenge and improving strategy for metal zinc anode are discussed, and the features of different aqueous electrolytes and the optimization solution are analyzed. Finally, the scientific problems to solve and technical challenges for the practical application in the future of this novel battery technology are summarized and prospected.

Organoboronic acids and esters are highly valuable building blocks in cross-coupling reactions and practical intermediates of various functional group transformations. Additionally, organoboronic acids can be utilized directly as small molecule drugs. Therefore, development of efficient methods to synthesize organoboronic compounds is of significant importance. Traditional pathways to synthesize organoboronic compounds mainly rely on electrophilic borylation of organometallic reagent and transition-metal-catalyzed borylation. Radical intermediates have unique chemical properties which are quite different from those of polar intermediates resulted from the heterolysis of chemical bonds and those of the organometallic compounds during transition metal catalysis. As such, borylation based on radical mechanism possesses distinctive reaction process, substrate scope, reaction selectivity, etc., and have great potential in synthesis of organoboronic compounds. In 2010, the Wang's group first reported borylation via a radical mechanism. This method realized an efficient direct conversion of anilines into aryl organoboronic esters. Inspired by this innovative work, more and more borylation methods via radical intermediates have been reported and developed as new avenues for C-B bond formation in the past decade. A series of studies show that organoboronic acids and esters could be efficiently constructed by the reaction of aryl/alkyl radicals with diboron compounds. In this paper, we summarize the recent development of borylation reactions via radical mechanisms, including aryl and alkyl radical borylation. As for aryl radical borylation, the activation of substrates containing C-N, C-O, C-S, C-X (X=halogen) bonds and carboxylic acids to C-B bond is summarized respectively. As for alkyl radical borylation, the activation of substrates containing C-N, C-O, C-X (X=halogen), C-C bonds and carboxylic acids to C-B bond is summarized respectively. Finally, we provide a perspective on the future development direction of this research area.

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.

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.

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.

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 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.

Ammonia is not only the main raw material of nitrogen fertilizer, but also a promising energy carrier for the storage and utilization of renewable energy. The fossil fuel-based Haber-Bosch ammonia synthesis industry is an energy-consuming and high CO₂-emission process. For the sustainable growth of human society, it is critically important to develop "green" ammonia synthesis processes driven by renewable energies. This scenario motivates growing interests on ammonia synthesis via heterogeneous catalysis, electro-chemical and photo-chemical routes as well as chemical looping process. Chemical looping ammonia synthesis (CLAS) process involves a series of individual reactions which produce ammonia in a distinctly different manner to the catalytic process. The CLAS could be operated under ambient pressure, and the switching on/off operation is flexible. Therefore, CLAS may be more amenable to variable and intermittent operation compared to the conventional catalytic process. More importantly, the competitive adsorption of N₂ and H₂ or H₂O in the catalytic process can be circumvented to a great extent, which opens new opportunities for the design and development of nitrogen carriers especially for low-temperature ammonia production. Because of these unique features, the application of chemical looping technology for ammonia synthesis has been received increasing attention in recent years. The development of high-efficiency nitrogen carriers is the key component for the implementation of CLAS. A wide range of materials including metal nitrides, metal imides, nitride-hydrides and oxynitrides have been evaluated as nitrogen carriers for CLAS. The knowledge accumulated during the past decade will no doubt beneficial for the further optimization and development of nitrogen carriers. This article reviews the research progress in the field of chemical looping ammonia synthesis in recent years, with the focuses on the materials development of nitrogen carriers in CLAS. Furthermore, the challenges and future directions of CLAS are also discussed. With the development of nitrogen carriers and process design, CLAS would potentially play an important role in the green ammonia synthesis as well as the future energy system.

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.

Reactive oxygen species (ROS) are categorized as a class of instantaneous intermediate products of oxygen, which are usually produced by a single electron continuous reduction of O₂. Examples include hydrogen peroxide (H₂O₂), superoxide anion (O₂^-), hydroxyl radical (HO·), hypochlorite radical (OCl^-) and singlet oxygen (¹O₂). The endogenous ROS arise from three major resources:mitochondrial electron transport chain (Mito-ETC), endoplasmic reticulum (ER) and NADPH oxidase (NOX). The produced ROS play vital roles in physiological functions including modulation of functions of proteins, regulation of cell signaling, mediation of inflammation, and elimination of pathogens. However, the cumulative ROS level in vivo could elicit oxidative stress, which is implicated in a multitude of diseases including cancer, autoimmune diseases, inflammation, cardiovascular diseases, neurodegenerative diseases. This abnormal biochemical alteration in tumors has inspired researchers to exploit the relatively high levels of ROS for development of ROS-responsive prodrug systems. In recent years, ROS-responsive prodrug systems based on a spectrum of ROS-sensitive linkers have been designed and developed with aim of precision tumor therapy. Herein, in this review, we would like to illustrate ROS-sensitive linkers developed to date including arylboronic acid or ester, alkyl thioether or selenide, thioketal, peroxalate ester, aminoacrylate, thiazolidinone and α-ketoamide, and elucidate the underlying molecular oxidation mechanism. Furthermore, the design of ROS-responsive prodrugs based on these sensitive linkers and their applications in anti-cancer therapy were reviewed. Additionally, the existing problems and the future research perspectives of prodrug systems were also discussed.

The levels of some biomolecules and ions in the body are usually related to the structural and functional changes of cells, tissues, organs, etc., which directly affect the prevention, diagnosis, and treatment of diseases. Therefore, in vivo bioassays of these substances are of great significance in medical and healthcare fields. The nano fluorescent probes consisted of rare earth nano materials have advantages of high sensitivity, simplicity, efficiency, and strong anti-interference ability, thus showing great potential in bioassays. The functionalization of aptamers on rare earth nanomaterials can further provide better specific recognition ability and biocompatibility for nano fluorescent probes, thereby enhancing their bioassays ability in complex samples. In this paper, the research progress of aptamer-functionalized rare earth nanomaterials as nano fluorescent probes in the field of bioassays is reviewed, and the main types, properties, detection mechanisms and detection substances are briefly introduced.

CuS@MoS₂ core-shell nanotubes were prepared by microwave-induced assembly techniques in the present work. Firstly, the Cu nanowires were vulcanized into hollow CuS nanotubes. Secondly, the sheet-shaped MoS₂ were uniformly intercalated and assembled onto the surface of CuS nanotubes. The as-prepared CuS@MoS₂ core-shell nanotubes were used in photocatalytic Fenton-like reaction system to remove high-concentration rhodamine B (RhB) in aqueous solution, which exhibited 100% degradation rate within 30 min under visible light (λ>420 nm) irradiation. The morphology and structure of the as-obtained catalysts were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectrometer (EDS) and X-ray diffractometry (XRD). UV-Vis absorption spectroscopy (UV-vis DRS) was used to characterize its basic optical properties. And to further learn the catalytic mechanism and make sure the active species of the photocatalytic Fenton-like reaction system, the heterojunction structure of the catalyst was analyzed and electron spin resonance (ESR) spectrum was carried to prove the existence of superoxide (·O₂^-) species. The high activity could be attributed to the unique multi-layer structure of CuS@MoS₂, corresponding to the enhanced absorption and exciting ability of visible lights. Meanwhile, the heterojunction structure formed between MoS₂ and CuS also promoted the transfer of photogenerated electrons, which could inhibit their recombination with photogenerated holes. More importantly, the cooperation mechanism formed between photocatalysis and Fenton-like reactions may exhibit strong promoting effect. The Cu²⁺ ions in CuS reacted with H₂O₂ to form a Fenton-like cycle, allowing the generation of reactive hydroxyl (·OH) species. While, the photogenerated electrons reacted with both the H₂O₂ and the molecular oxygen activated by MoS₂ to produce ·OH and ·O₂^- species. Both ·OH and ·O₂^- species worked together to oxidize pollutants rapidly. This work developed a recycled photocatalytic Fenton-like reaction system, which may offer new pathway for the treatment of environmental pollution.

Secondary organic aerosol (SOA) is a major component of aerosols in the atmosphere, which plays a crucial role in climate change, regional pollution and human health. Laboratory simulations are usually used to mimic SOA formation. The most commonly used simulation facilities are environmental chambers and potential aerosol mass (PAM) reactors. Here in this work, we review the studies about influencing factors and mechanisms of SOA formation, as well as the evolution of SOA aging. We summarize the influencing factors on SOA yields, i.e. OH exposure, NO_x level, and the loading and chemical composition of seed particles. The effects of NO_x level (i.e. VOCs/NO_x) and OH exposure are nonmonotonic. The NO_x level influences the fate of RO₂ radicals, so SOA yields will increase and then decrease with the addition of NO_x. Similarly, the increase of OH exposure affects the major oxidation mechanism from functionalization to fragmentation, leading to the up and down trend of SOA yields. The higher seed particle loading provides more surface area for condensable products and then increases the SOA yields. The particle acidity favors the uptake process for gas-phase products and promote the SOA formation via further reactions in the condense phase. Trace components e.g. transition metals and minerals can be involved in the SOA formation and aging by catalysis or affecting the uptake of oxidants and their products. Chambers and PAM reactors are usually used to explore SOA formation potential of different sources. SOA formation potential from vehicles will be influenced by engine types, engine loading and composition of fuel. The highest SOA enhancement ratio (SOA/POA) from gasoline engines is about 4~14, when the equivalent photochemical days are 2~3 d. The SOA production mass from gasoline vehicles is from about 10~40 to 400~500 mg/kg fuel. The SOA formation potential is about 400~500 mg/kg fuel. The largest SOA enhancement ratio for biomass burning is 1.4~7.6, which occurs at 3~4 photochemical days. The SOA enhancement ratio from ambient air differs from region to region. However, the highest ratios all occur at the photochemical age of about 2~4 d. We summarize the SOA characteristics evolution with aging. Oxidation state of particles will increase with OH exposure. Changes of H/C and O/C with increasing OH exposure can be plotted in the Van Krevelen diagrams. The slopes of fitted curve range from -1 to 0, indicating OA evolution chemistry involving addition of carboxylic acids or addition of alcohols/peroxides. In addition, the volatility and hygroscopicity of oxidized OA will be higher than primary organic aerosols. In the future, more studies should be focused on developing new technologies to measuring the oxidized intermediate products at a molecular level. Also the researches on the mechanism of SOA formation from complex precursors are also crucial to understand the SOA formation at real atmosphere.

In past decades, global warming, sea level rising, and other climate problems caused by greenhouse effect are becoming more and more serious. Considerable efforts have been paid on developing new technology that can effectively reduce the atmospheric level of carbon dioxide (CO₂), the most representative one of greenhouse gases. Solar-driven conversion of CO₂ into high value-added hydrocarbon fuels is considered as the most promising approach to alleviate the current energy crisis and the rising CO₂ level. Benefiting from their high specific surface area and novel electronic structures, two dimensional (2D) materials have drawn intense interest in the field of CO₂ photoreduction. Herein, the latest development of 2D materials for photocatalytic CO₂ reduction is presented, with special emphasis given to the structure-activity relationship in catalytic reactions. The potentials of newly emerged 2D materials including black phosphorus, graphdiyne and covalent organic frameworks as the next generation photocatalysts for CO₂ reduction are then discussed. Finally, the opportunities and challenges in the field of CO₂ photoreduction are featured on the basis of its current development.

Double-network (DN) hydrogels are composed of two asymmetric networks with contrasting properties, wherein the rigid and brittle network serving as sacrificial bonds effectively dissipates energy to enhance the mechanical performance. The first reconstructable physical network endows the DN hydrogels with outstanding anti-soften and mechanical stability. However, the monotonous type of physical networks and the difficulty in tailoring structure and mechanics greatly limit the development and application of DN hydrogels. Focusing on these problems, we have fabricated the rigid and brittle chitosan physical network with adjustable network type, structure and property and further constructed various chitosan-based DN hydrogels with high mechanical performance and tunable mechanics. The hydrogels were potential materials for anti-freezing dresses, biomedical materials, flexible electronics and wearable devices. The universal strategy of constructing chitosan-based DN hydrogels was beneficial for developing various functional and high-mechanical hydrogels and broadening their applications.

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.

Nowadays malignant tumors are still one of the disastrous diseases. It is necessary to explore new strategies for the treatment of malignant tumor. Nanomaterials refer to materials with at least one dimension of the three dimensions in the nanometer range (1~100 nm). They show a wide range of applications in tumor treatment while disadvantages of low targeting efficiency, poor tumor penetration and obvious side effects still limit their applications. As a method for tumor treatment, bacterial therapy has a long history. Some facultative anaerobic and obligate anaerobic bacteria and their secretions have the characteristics of targeting hypoxic tumor tissue, strong tumor penetration and stimulating immune responses. After genetically modification or attenuation treatment, it can be used for tumor treatment. However, the safety issues and low therapeutic efficiency still needs to be solved. The combination of nanomaterials and bacteria can complement the limitation of each other, and shows great potential in tumor therapy. On one hand, bacteria could enhance the targeting efficiency of nanomaterials, and decrease the side effects. On the other hand, nanomaterials could help improve the safety and solve the problem of low therapeutic efficiency of bacterial therapy. In this review, the combination of nanomaterials and bacteria is divided into three categories based on the role of bacteria in the treatment. Firstly, the preparation of composites of nanomaterials and bacteria by chemical bonds, electrostatic interaction, and other ways to enhance tumor targeting. Secondly, bacterial enzyme could react with nanomaterials to control the release of drug. Thirdly, secretions of bacteria after plasmids were introduced and outer membrane vesicles secreted by bacteria could be combined with nanomaterials for anti-tumor therapy. The mechanisms of the combination therapy are also discussed. Finally, we summarized and discussed the current challenges, especially the safety of the combination therapy. The prospect of the combination of nanomaterials and bacterial for tumor treatment is also proposed.

Attempts to synthesize the 4,5-spirocycle skeleton of Phainanoids by rhodium-catalyzed arylative cyclization of alkynone 5 and the addition of Grignard reagent 9 to α-alkoxyl cyclobutone 8, followed by intramolecular S_NAr reaction are reported. Phainanoids, highly modified triterpenoids, were isolated from Phyllanthus hainanensis by Yue and co-workers. They have been found to show intriguing immunosuppressive activities. The most potent of them, Phainanoid F, inhibit the proliferation of T cells with an IC₅₀ value of (2.04±0.01) nmol/L and B cells with an IC₅₀ value <(1.60±0.01) nmol/L. The noteworthy activities and the lack of Phainanoids in nature resources make the synthesis of them for further biological evaluation a challenge for chemists. Our synthesis started from known compound 1, after Birch reduction and alkylation to give alkynone 5. The rhodium-catalyzed arylative cyclization of alkynone 5 to deliver tetrasubstituted cyclobutene 6 was performed by the following procedure. Under an atmosphere of Ar, to an oven-dried Schlenk tube with[Rh(OH)(cod)]₂ (35.5 mg, 0.078 mmol, 0.012n₅), phenylboronic acid (2.0 g, 16.3 mmol, 2.5n₅), were added a solution of ketone 5 (1.9 g, 6.5 mmol, 1.0n₅) in 1,4-dioxane (32.0 mL) and H₂O (0.3 mL) at room temperature. The mixture was stirred at 35℃ for 12 h. Another [Rh(OH)(cod)]₂ (35.5 mg, 0.078 mmol, 0.012n₅) and phenylboronic acid (2.0 g, 16.3 mmol, 2.5n₅) was added to the mixture. The mixture was stirred at 35℃ for 12 h. Subsequently, hydroxyl group was protected with ethoxymethyl (EOM) group to furnish 7, followed by ozonolysis to generate ketone 8. Ketone 8 was reacted with fresh prepared Grignard reagent 9 in Felkin-Anh modelinstead ofthe Cram's chelation-control model to deliver alcohol 10. The explanation of the diastereoselectivity of this reaction could be illustrated from two aspects:(1) the rigid structure of α-alkoxyl cyclobutone 8 increased the energy barrier for the transition state of chelation between magnesium ions and alkoxyl substituent; (2) the magnesium ions were not chelated with the alkoxyl substituent as well as the carbonyl oxygen was due to the intramolecular chelation with fluorine atom. Alcohol 10 underwent intramolecular S_NAr reaction and deprotection to deliver 4,5-spirocycle compound 18.

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.

Stretchable organic electronic devices are characterized with high mechanical stability, superior electronic stability, low cost, satisfactory biocompatibility, etc., thus having been regarded as an inevitable trend in the development of future electronics. Furthermore, the functional stretchable organic electronic devices provide pathways toward the emerging high-tech fields such as wearable and implantable devices, intelligent medical diagnosis system, software robots, etc. This review focuses on the research advances in functional stretchable organic electronic devices, including stretchable organic transistors (field-effect transistors, phototransistors, memory transistors and sensors), stretchable organic optoelectronic devices (light-emitting diodes, alternating current electroluminescent devices and light-emitting electrochemical cells), stretchable organic energy storage and conversion devices (solar cells, supercapacitors and nanogenerators), stretchable organic sensors (pressure sensors, strain sensors, tactile sensors, temperature sensors, gas sensors and other sensors), stretchable organic memory (resistive memory, magnetic memory and bionic synaptic memory) and other functional stretchable organic electronic devices. Finally, through the analyses of the existing scientific problems and future development of the functional stretchable organic electronic devices, we put forward some suggestions.

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.

Polymerization-induced self-assembly (PISA) is one of the most cutting-edge strategies towards the preparation of nanoparticles with a range of morphologies (spheres, worms, vesicles, etc.) as it combines polymerization and self-assembly and thus can afford high solid contents in various media. Additionally, nanoparticle morphology can be accurately targeted by adjusting the degree of polymerization of the soluble stabilizer block and the insoluble core-forming block, as well as solid contents in PISA formula. Unfortunately, this highly efficient approach is limited to specific polymerization methods, and hence specific monomer types. Currently, PISA based on reversible addition-fragmentation chain-transfer polymerization (RAFT) has been well-established for the in situ preparation of a range of nanoparticle morphologies. This method is relatively mature especially in the mechanism exploration, morphological control, and characterization, which has important impact to other fields of polymer chemistry. However, methacrylates, acrylates, and styrene monomers are often essential for reversible addition-fragmentation chain-transfer polymerization-induced self-assembly (RAFT-PISA), leading to the carbon-carbon backbone, which normally produces nonbiodegradable structures. These drawbacks are detrimental in terms of biomedical applications. Fortunately, new PISA strategies based on ring-opening polymerizations, including ring-opening metathesis polymerization-induced self-assembly (ROMPISA), ring-opening polymerization of N-carboxy- anhydride-induced self-assembly (NCA-PISA) and radical ring-opening polymerization-induced self-assembly (rROPISA), have been developed to overcome these problems. ROMPISA has proven to be an efficient approach for fabricating multifunctional nanoparticles due to its great tolerance for many functional groups. Biodegradable nanoparticles, including spheres and vesicles, have been successfully prepared by rROPISA and NCA-PISA. Therefore, ring-opening PISA (ROPISA) provides not only new polymerization methods but also new strategies for fabricating biodegradable nanoparticles with a range of monomer species. In this perspective, we briefly summarize the current progress and analyze the challenges of ROPISA. Finally, we provide a perspective for the further development of ROPISA addressed on the mechanism, monomers and applications, which provides an insight into ROPISA as well as some suggestions and directions for its future research.

Artificial intelligence (AI), especially the machine learning, is playing an increasingly important role in contemporary scientific research. Unlike the traditional computer program, machine learning can analyze a large number of data repeatedly and optimize its own model, a process which is called a "learning process". So that the AI can find the relationship underling the experiments from a large number of data, form a new model with better prediction and decisionmaking ability, and make an optimized strategy. The characteristics of chemical research just hit the strengths of machine learning. Chemical research often faces very complex material system and experimental process, so it is difficult to accurately analyze and making judgment through physical chemistry principles. Artificial intelligence can mine the correlation of massive experimental data generated in chemical experiments, help chemists make reasonable analysis and prediction, and therefore greatly accelerate the process of chemical research. This review presents the modern artificial intelligence method and its basic principles on solving chemical problems, by representative examples with specific machine learning algorithm. The application of artificial intelligence in chemical science is in a period of vigorous rise. Artificial intelligence has initially shown a powerful assist to chemical research. We hope this review can help more domestic chemical workers understand and use this powerful tool.