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.

Molecular electronics is an interdisciplinary science that mainly studies the charge transport through molecules and its main goal is to fabricate molecular devices with electrical functionalities. In the state-of-art of molecular electronics, the research paradigm is to fabricate electrodes pair with nanometer-sized separation and construct the molecular junction through the assembly of target molecules with the electrodes pair. With this framework, the target molecule can be integrated to the macroscopic measurement circuit. DNA is one of the most significant biomolecules in natural sciences. It had drawn great attentions in biomedicine because of the carried genetic instructions. In molecular electronics, DNA also had attracted much interest due to the distinct structure and its capability of long-range charge transport. Nevertheless, in the early stage of molecular electronics, the probe molecules were limited to those with simple structures and short lengths. In recent years, molecular electronics had witnessed a rapid progress due to the developments in micro/nano-fabrication and the detection for weak current signal. Specifically, it includes the improvements in the success rate, efficiency, and stability of the fabricated molecular device. Benefiting from that, the probe molecules had been extended to a number of complex compounds like DNA. We give a brief introduction to the recent progress in the fabrication of DNA molecular junctions and the studies on the corresponding charge transport, most of which were made by using the research paradigm of fabricating electrodes pair with nanometer-sized separation. According to the fabrication methods that employed, these advances were introduced in two classes. One is that made by the as-called break junction methods, which include STM-break junction, conductive AFM and mechanically controllable break junction. The other is that made by the as-called cutting methods, which include cutting of carbon nanotube, graphene and silicon nanowire. We summarize the historical development of these methods and give a comparison between them. We also introduce some representative research on the charge transport through DNA molecular junction, and discuss the distinct features of DNA in electrical properties compared to the conventional small molecules. To conclude, we give a prospect on the future development of the studies on charge transport through DNA molecular junction.

Optically pure alkylnitriles are important structural motifs found in agrochemicals, pharmaceuticals, and natural products, which can be further transferred to acids, amines and amides. Direct asymmetric cyanation of sp ³ C—H bonds represents the most efficient synthetic pathway to these optically pure alkylnitriles. However, selective functionalization of sp ³ C—H bonds remains a crucial issue due to the inertness of sp ³ C—H bonds as well as the difficulties in the control of stereo- and regioselectivity. Inspired by enzymatic oxygenases and halogenases, such as cytochrome P450 and nonheme iron enzymes, the radical-based C—H functionalization has received much attention, which was initiated with a hydrogen atom transfer (HAT) process. Recently, numerous reports have been disclosed for the highly efficient functionalization of C—H bonds with an intramolecular HAT process as a key step to govern the reactivity and site selectivity. Our group has developed a copper-catalyzed radical relay process for the enantioselective cyanation and arylation of benzylic C—H bonds using TMSCN and ArB(OH)₂ as nucleophiles respectively. Mechanistic studies indicated that a benzylic radical generated via a radical replay process can be trapped by a reactive chiral copper(II) cyanide enantioselectively, delivering optically pure benzyl nitriles efficiently. Herein, we communicate the catalytic asymmetric cyanation of remote C—H bonds by merging photoredox catalysis with copper catalysis. This reaction proceeds under mild reaction conditions and exhibits good functional group compatibility as well as wide substrates scope. Additionally, the nitrile group was further reduced to amide under hydrogen atmosphere. This reaction provides an efficient pathway to synthesize chiral δ-cyano alcohols and 1,6-amino alcohols. The general procedure is as following: in a dried sealed tube, substrate 1 (0.2 mmol, 1.0 equiv.), Cu(CH₃CN)₄PF₆ (0.01 mmol, 5 mol%), L (0.015 mmol, 7.5 mol%) and Ir(ppy)₃ (0.002 mmol, 1 mol%) were dissolved in dichloromethane (4.0 mL) under N₂ atmosphere, and stirred for 30 min. Then, TMSCN (50 μL, 0.4 mmol, 2 equiv.) was added slowly under N₂ atmosphere. The tube was sealed with a Teflon-lined cap, and the mixture was stirred under the irradiation of blue LED for 1~7 d. The reaction mixture was diluted with dichloromethane, filtered through a short pad of celite. A solution of TBAF (3 equiv.) and HOAc (3 equiv.) was added to the filtration. The mixture was stirred for 5 min and then washed with water (3×10 mL) and dried over anhydrous Na₂SO₄. After filtration and concentration, the residue was purified by silica gel chromatography (eluent: petroleum ether/ethyl acetate) to afford target product.

Nanopore technology are being developed for large areas in life science, not only in DNA sequencing and protein sequencing, but also in biomolecule detection, bio-interaction measurement and drug screening. Aerolysin is regarded as new powerful tool for oligonucleotide sensing and peptide sensing due to its high charged pore lumen. Applied a transmembrane potential with a pair of Ag/AgCl electrodes, the negatively charged oligonucleotides are driven into the aerolysin nanopore, inducing a series of ionic current blockages, which could distinguish the oligonucleotides with different length or single base variation. However, due to the lack of high-resolution structure of aerolysin nanopore, the mechanism of its high sensing capability is not clear, limiting the further applications of aerolysin. Recently, we presented two sensing regions inside aerolysin, R1 (near R220) and R2 (near K238), having huge influences on oligonucleotide sensing. Especially, the R1 is responsible for distinguished all 4 bases and 2 modified based in the mixture. However, the detailed mechanism of synergistic effect for these two regions in detection of single nucleotides is still unclear. Here, we use dA₁₄-4-X, dA₁₄-11-X, dA₁₄-4-X-11-X (X=C, T, G) as probes to investigate the effects of base types on the sensing ability of R1 and R2. The results show that the A, C or T in R2 region did not change the sensing ability of R1 region, while G in R2 would hinder the base discrimination in R1 region. This may be caused by the large volume of G that would nearly fully occupy the R2 region and the stronger non-covalent interaction between G and R2 region, resulting in determining the residual current of the whole nanopore. Moreover, we evaluated the interaction between different bases with the sensing region. The results show that the interaction is independent with the volume of the bases, which is ordered by A>G>C>T, suggesting the interaction inside the aerolysin lumen is a considerable factor for its sensing capability. These results would guide us to directly design the mutant Aerolysin nanopore that aims for DNA sequencing and peptide sequencing.

Covalent organic frameworks (COFs) are a class of porous crystalline materials consisting of organic units connected through covalent bonds. Due to their low density, high surface area and high thermal stability, COFs have found interesting applications in many fields, including molecular adsorption and separation, sensing, catalysis and optoelectronics devices. In particular, two-dimensional (2D) COFs have attracted increasing attention in energy fields. In this perspective, the applications of 2D COFs in energy storage (lithium ion batteries, lithium-sulfur batteries, supercapacitor and fuel cells) and energy conversion (water splitting and reduction of carbon dioxide) are reviewed. In addition, we will also discuss the remaining challenging issues.

Since the introduction of perovskite solar cells in 2009, perovskite solar cells have developed rapidly due to their low-cost and high theoretical photoelectric conversion efficiency. Among them, the inverted structure of perovskite solar cells has received more and more attention due to its good stability and low hysteresis effect. Since its inception in 2013, its photoelectric conversion efficiency has rapidly increased from the initial 3.9% to 21.5%. However, compared with the traditional upright structure perovskite solar cells, there is still a gap in the photoelectric conversion efficiency of inverted perovskite solar cells. Due to the nature of the organic materials used, perovskites are more severely affected by moisture in the air environment. They are heavily dependent on nitrogen protection during device manufacturing. In the future, if perovskite solar cells are put into production, the fully enclosed waterless environment will obviously increase the production costs. At the same time, the development of large-area preparation technology is still a difficult problem to be solved. The development of inverted perovskite solar cells, the selection of carrier transport materials, interface optimization, and the development of flexible devices are systematically reviewed in this paper. For example, PEDOT:PSS was doped by GeO₂ and DMSO, and PEDOT:PSS was modified by MoO₃ and GO to improve its work function, acidity and hygroscopicity. A NiO_x dense layer is usually doped with Mg ²⁺, Li ⁺ and Cs ⁴⁺ to increase its conductivity, which can be prepared by different methods such as magnetron sputtering and sol-gel method. The PCBM interface is modified by C₆₀, BCP, LiF etc., to enhance its ohmic contact with the metal counter electrode. And the PCBM is doped by graphene, CoSe, SnO₂ etc., to reduce the charge recombination caused by the interfacial resistance and the defects of the perovskite film. This paper would provide a way to obtain a high efficiency inverted perovskite solar cells by structure and material optimization. And it also give insights into the general rules for preparing large area and flexible devices.

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.

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.

The production and transformation of alkynes occupys an important position in organic synthetic chemistry. Within this realm, propargylic functionalization of alkynes is a feasible way towards this purpose. Especially, the propargylic functionalization via radical pathways has flourished in the last decade, which is believed to be a significant complement to the classic metal-catalyzed propargylation reaction involving cationic intermediates. According to the reaction modes, these advancements will be highlighted by classifying into four types. The first one is the propargylic functionalization reactions involving propargylic radicals. Generally, propargylic radicals can be generated through single electron reduction of alkyne substrates by low-valence metal catalysts or excited state of photocatalysts, then participated in the following cross-coupling reactions to achieve alkyne products. In this part, asymmetric variants have been also well developed. The second one is the preparation of allene compounds through the allenyl radical pathway. For these processes, propargylic radicals can isomerize to allenyl radicals, which can participate in the copper- or nickel-catalyzed coupling reaction to produce significant allene compounds. The third one is the dehydrative alkylation reaction of propargyl alcohols that involve propargylic radical intermediates, too. Such radical intermediates can be further oxidized to propargylic cation intermediates, followed by a deprotonation to form substituted 1,3-enyne compounds. The forth one is the synthesis of vinylic alkoxyamines through a propargylic radical route. Initially, propargyl alcohols can be converted to propargylic radical species by the joint action of copper catalysts and TEMPO. The generated propargylic radical species can be captured by TEMPO to form vinylic alkoxyamines. Finally, an outlook on the radical propargylic functionalizations will be provided at the end of this review.

Allylic substitutions catalyzed by transition metals are important and practical reactions, which can construct carbon-carbon bonds and carbon-heteroatom bonds efficiently and stereoselectively. Various transition metal catalysts, such as Pd, Ir, Cu, Ni, Rh and Ru, have been widely used in this reaction. To date, various “soft”, or stabilized nucleophiles (pKa<25), including malonates, acetoacetates and enolates, have been used in allylic substitutions. Conversely, the high reactivity of “hard”, or non-stabilized alkyl nucleophiles (pKa>25) has limited their utility in catalytic processes and their compatibility with functional groups. Visible light photoredox catalysis has been widely used in organic synthesis because it can generate high reactive intermediates, such as free radicals and radical ions, under mild conditions using green and clean energy, and has gradually developed into an important synthetic tool. Furthermore, merging photoredox catalysis with transition metal catalysts has become a popular strategy for expanding the synthetic utility of visible-light photocatalysis, and has led to the discovery of novel reaction modes. Due to the high activity of the intermediates in photoredox catalysis, the selectivity of these reactions, especially stereoselectivity, is still a challenge. In view of the importance of allyl substitutions, the allyl substitution co-catalyzed by transition metals and photoredox has attracted the interest of chemists. The synergistic strategy can realize allylic substitutions which are difficult to be achieved by single transition metal catalysis. The regioselectivity and stereoselectivity of these reactions also show different characteristics. It is expected to become an important complement to allylic substitution catalyzed by single metal. In this review, recent advances on allylic substitution co-catalyzed by different transition metals and photoredox are summarized. Meanwhile, the mechanism of representative transformations will be briefly introduced and the prospective in this area will be given.

CO₂ is an ideal C1 source in chemical transformations. It is of great significance to utilize CO₂ in chemical conversion to synthesize high value-added compounds, including carboxylic acids and carbonyl-containing heterocycles. On the other hand, the difunctionalization of olefins is an important organic reaction, which can efficiently convert easily available olefins into important compounds with structural diversity. However, due to the low reactivity of CO₂ and the difficulty in controlling the selectivity, the difunctionalization of olefins with CO₂ is highly challenging. Recently, the significant progress of radical chemistry has provided new strategies and promoted the development of novel transformations in this field. This Perspective summarizes the recent progress of the radical-type difunctionalization of olefins with CO₂, including the oxy-alkylation, carbocarboxylation, silacarboxylation, thiocarboxylation, and dicarboxylation of alkenes with CO₂. At the same time, we also highlight the mechanism with radicals and four kinds of pathways are proposed: (1) Free radicals attack olefins to form new carbon radical intermediates. The radicals are then oxidized to form carbocations, which are further captured by carbonates or carbamates. It is also possible for direct C—O bonding reaction or sequent C—I and C—O bonds formation. (2) The new carbon radical intermediates, in-situ generated through attack of alkenes with radicals, are reduced via single electron transfer into carbanions, which could attack CO₂ to form C—C bonds. (3) CO₂ is reduced into CO₂ radical anions in the highly reductive reaction conditions. Once generated, the CO₂ radical anions might attack olefins to form carboxylate bearing more stable carbon radical intermediates (such as benzylic ones) and further form C—C bonds or carbon-heteroatom bonds. (4) Olefins are reduced via single electron transfer into alkenyl free radical anions in the highly reductive reaction conditions. These anions may attack CO₂ to form carboxylate bearing carbon radical intermediates and are further reduced to generate carbanions. Finally they may attack another CO₂ to form succinic acid derivatives. We point out the challenges and predict the future development in the field, including the more challenging substrates, more reaction types, better selectivities, and deeper mechanistic understanding.

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.

Hantzsch Esters were first synthesized by Arthur Rudolf Hantzsch in 1881, and widely used in pharmaceutical chemistry. The application of Hantsch Esters in organic synthesis in the early time was mainly focused on the dehydrogenation of 1,4-dihydrogen pyridines (DHPs) in the synthesis of functional pyridines. In 1955, Mauzerall and Westheimer found that Malachite Green could be reduced by Hantzsch Esters to generate the hydrogenated product. Then these DHPs were extensively used as a reductant for decades due to their electron and hydrogen donating properties. In recent years, scientist found that C—C bond cleavage at 4-position of 4-substituted Hantzsch Esters would lead alkyl transfer, and the alkylation process was a radical process. With the rapid development of free radical chemistry, various alkylation reactions using 4-substituted Hantzsch Esters as alkylation reagent have been developed, such as addition reactions of imines and alkenes; cross-coupling reactions with aryl halides; substitution reactions with functional aromatics; Tsuji-Trost reaction; radical insertion with sulfur dioxide; and asymmetric alkylation etc. The advantages in alkylation transfer by using 4-substituted Hantzsch Esters as alkyl source in the past five years were witnessed dramatically: (1) Highly toxic alkyl metal reagents could be avoided in the alkylation reactions; (2) Compared with the moisture sensitivity of alkyl metal reagents Hantzsch Esters are easily handling; (3) 1,4-Dihydrogen pyridines (DHPs) are biologically-inspired model molecular of reduced nicotinamide adenine dinucleotide (NADH), which would expand the application in biosynthesis. A brief summary in this field is presented in this review, and the advances are classified according to different reaction types. Although these creativity works were developed, there are still some challenges: (1) Could aromatic groups at 4-position of 4-substituted Hantzsch Esters serve as arylation reagents? (2) How to recover the rest pyridine part of Hantzsch Esters after alkylation; (3) New type reactions need to be developed for the asymmetric synthesis.

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.

Molecular-scale electronics studies the charge transport properties across molecules by constructing "elec-trode-molecule-electrode" junctions based on the molecular electrodes and single molecule or small amounts of molecular aggregates. It examines the structure-property relationship between the physical and chemical properties of the molecule and the charge transport by combining the intrinsic chemical properties of molecule with device architecture, reveals the micro-scale quantum transport mechanics principle, and explores molecular-based functional electronic devices. It is a research field that integrates chemistry, physics and microelectronics. In this review, we summarize some of the representative progress of molecular electronics in basic research (device preparation, transport mechanism) and applications in recent years.

The intramolecular aromatic ring systems migration reactions, namely Smiles rearrangement is a powerful method for (hetero)aryl group functionalization. It can be employed as a complementary strategy to arene functionalization, and has found its broad applications in synthetic chemistry. After the initial documentation in 1894 this chemistry was intensively investigated by Smiles. In its classical pathway, the migration of aromatic ring system takes place ipso nucleophilic substitution. Accordingly, the migrating (hetero)aryl groups are highly electronic and steric-dependent. Moreover, as new reaction modes reported, advances have been made in the areas for arene C—C, C—N and C—O bond formation and radical triggered Smiles rearrangement has also enriched migrating units. Recently, there has been a rapid growth in the transformation induced by visible-light photocatalysis. Harnessing visible light as the energy source for chemical reactions usually serves as an environmentally benign alternative in comparison with classical radical pathway. Furthermore, photoredox-induced rearrangement represents a valuable and efficient approach for facilitating both the radical-based bond-cleaving and bond-forming events in a single step. It has become an effective tool for both synthesis and late stage modification of bio-active molecules. The last five years has witnessed many important advances in exploring photo-induced Smiles reactions, which make this classic reaction regained its attention. Significant progress has been made for expediting the generation of N-centered, C-centered and O-centered from a variety of precursors before single electron transfer rearrangement. This powerful synthetic platform for efficient promotes (hetero) aromatic group construction under mild reaction conditions, and has become a useful method for the synthesis and late stage functionalization of pharmaceutically interest products. In this perspective, we focus on visible light induced Smiles chemistry, which the major breakthroughs are classified based on migrating-induced radical species, and their synthetic applications are discussed briefly.

Polysaccharides are a class of bio-macromolecules with highly complex structures that are widely found in living organisms such as microorganisms, plants and animals. Polysaccharides serve not only as structural components and energy sources of cells, but also as important signaling molecules which are involved in many key biological processes. Studies on polysaccharide-mediated biological processes require access to structurally defined molecules, which approach the size and complexity of those found in nature, but naturally-occurring polysaccharides usually exist in microheterogeneous forms, making it difficult or even impossible to isolate pure polysaccharides from natural sources in most cases. Chemical synthesis represents a reliable solution to this problem, which can provide polysaccharide samples with defined chemical structures for functional studies and even a library of analogs of natural glycans for structure-activity relationship investigations. But unlike oligonucleotides and peptides, which can already be obtained by automated synthesizers in a very short of time, the chemical synthesis of glycans remains a great challenge for synthetic chemists. The major challenge for glycan synthesis lies in the need to handle both stereo-and regio-chemistry in the construction of each glycosyl linkage, and the extensive protecting-group manipulations as well as much intermediate separation make it a tedious and time-consuming process. Over the past decades, carbohydrate chemists have developed many glycosylation reactions. A series of strategies for glycan assembly have been also established. The advances in both synthetic methods and strategies have significantly increased the synthetic efficiency of carbohydrate molecules, and many great accomplishments in the field of polysaccharide synthesis have been witnessed in recent decades. Some representative methods and strategies, and their successful applications in the chemical synthesis of complex polysaccharides are summarized in this review.

Catalytic synthesis of organic sulfinamides has great significance and value in organic synthesis, material science, and bioscience. Traditional synthetic methods for sulfinamides are often confronted with various challenges, such as tedious reaction steps, harsh reaction conditions. Direct activation of S—H and N—H bonds to synthesis sulfinamides is the most effective and atomic economic way, which can realize the N—S bonds construction without pre-functionalization of the substrates. To establish a versatile and efficient technology for such reaction, an electrochemical cross coupling hydrogen evolution (CCHE) reaction, which is often used as an environmentally friendly and efficient way to construct new bonds, for synthesis of sulfinamides has been successfully developed by using thiols and amines as the easily available and inexpensive substrates. A series of sulfinamides were prepared with excellent yields and good compatibility of functional groups under extremely mild reaction conditions. Experimental results showed that sulfenamides, which were constructed as intermediate products via radical pathway, were further oxidized to sulfinamides. H₂ ¹⁸O labeling experiment confirmed that the oxygen of sulfinyl group comes from the trace water in 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP). In addition, tetrabutylammonium iodide (TBAI) played important dual roles of intermediate and electrolyte in this reaction system. The typical procedure is as follows: A 20 mL oven-dried reaction vital equipped with a magnetic stir bar was charged with thiol 1 (0.2 mmol), amine 2 (0.3 mmol) and TBAI (0.05 mol/L) in HFIP (5 mL), and exhausted via puncture needle for 15 minutes with argon. The mixture was then electrolysed with carbon foam plate (anode) and platinum plate (cathode) as the electrodes in an undivided cell for 6 hours in 10 mA constant current at room temperature. After the reaction, the mixture was evaporated under reduced pressure to remove the solvent and the residue was purified by chromatography on silica gel to get the desired sulfinamide 3.

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.

Axial chirality is of significant importance in chiral molecules. Axially chiral biaryls are existed in numerous natural products and biologically active molecules. Moreover, they have been extensively used as chiral catalysts and chiral ligands in asymmetric catalysis. Due to the importance of these privileged scaffolds, considerable attention has been attracted to develop novel, efficient and practical methods for their asymmetric synthesis by utilizing chiral transition-metal catalysis or chiral organocatalysis. Among those reported elegant achievements, asymmetric C—H bond functionalization reactions are the most concise and efficient methods for the synthesis of axial chiral biaryls in terms of atom and step economies. With the advancement of transition-metal-catalyzed asymmetric C—H bond functionalization reactions, they largely promote the field of asymmetric synthesis of axially chiral biaryls. Recent progress on the development of synthesis of axially chiral biaryls via transition metal (Pd-, Rh-, and Ir-) catalyzed asymmetric C—H bond functionalization reactions are summarized in this review. Those mainly include:Rh-catalyzed enantioselective C(sp²)-H bond alkylation and arylation reactions with the combination of rhodium (I) catalyst precursors and chiral phosphine ligands; Rh-catalyzed enantioselective C(sp²)-H bond alkenylation, arylation and annulation reactions with well-defined chiral rhodium (Ⅲ)-Cp(SCp) complexes; Ir-catalyzed enantioselective C(sp²)-H bond arylation reactions with chiral iridium (Ⅲ)-Cp complex and chiral amino acid as co-catalyst; Pd-catalyzed diastereoselective C(sp²)-H bond alkenylation, iodination, and arylation reactions using chiral p-tolyl sulfoxide auxiliary or menthyl phenylphosphate group as a directing group; Pd-catalyzed intramolecular enantioselective C(sp²)-H bond arylation reaction with Pd(0) catalyst precursors and chiral TADDOL-phosphoramidites; Pd-catalyzed intermolecular enantioselective C(sp²)-H bond iodination, alkenylation, alkynylation, allylation and arylation reactions with Pd(Ⅱ) catalyst precursors and mono-N-protected amino acids (MPAAs). In addition, preparation of varieties of novel axially chiral ligands by utilizing these methods and their applications in catalytic asymmetric reactions are also covered. Meanwhile, applications of these methods as key steps in the synthesis of natural products are also discussed.

The reduction of esters to alcohols is one of the most important chemical transformations in the production of fine chemicals, such as pharmaceuticals, agricultural chemicals, fragrances, and biofuels. Homogeneous catalytic hydrogenation of esters represents a green, atom-economic, and sustainable alternative to conventional stoichiometric approaches, avoiding the generation of large amount of wastes and the difficulties arose in work-up procedure by using metal hydride reductants. Although challenges still exist, significant progress has been made in catalytic hydrogenation of esters over the last ten years. Numerous transition metal catalysts including noble metal (such as ruthenium, osmium, and iridium) complexes and base metal catalysts (such as iron, cobalt, and manganese) have been developed for the hydrogenation of esters. The ligands of the catalysts have been well studied. A wide range of bidentate ligands including diamines, amino-phosphines, pyridine-amines, N-heterocyclic carbene-amines, and bipyridines, tridentate pincer ligands containing diethylamine and pyridine skeletons, tetradentate ligands containing pyridine and bipyridine skeletons have been applied in the hydrogenation of esters. The efficiency of hydrogenation of esters has been significantly improved, and the highest turnover number (TON) reached 90000 for the hydrogenation of benchmark substrates such as ethyl acetate, ethyl benzoate, and γ-valerolactone. A significant breakthrough has also been made in the catalytic asymmetric hydrogenation of esters to chiral primary alcohols. The asymmetric hydrogenations of ketoesters, racemic δ-hydroxyesters, and racemic α-aryl/alkyl substituted lactones provided efficient methods for the asymmetric synthesis of optically active chiral diols including chiral 1,5-diols and 1,4-diols. The significant progress achieved in recent years in the area of homogeneous catalytic hydrogenation of esters to alcohols is presented in this review. The focus of this review are the development of ligands and catalysts, and the advances in the catalytic asymmetric hydrogenation of esters and lactones.

As inexpensive and readily available feedstocks, alkenes possess a unique reactivity profile and thus have been extensively applied in synthetic chemistry. Specifically, radical-triggered difunctionalization of alkenes provides a valuable synthetic strategy for their high utilization by incorporating two functional groups across the C=C π system. Despite the great achievements gained in this field, the vast majority of well-developed methods generally focus on activated alkenes, because its nascent alkyl radical needs to be stabilized by adjacent functional groups (e.g. aryl, carbonyl, heteroatom) via p-π conjugate effect. However, radical induced difunctionalization of unactivated alkenes remains elusive. Herein, a new protocol for Fe(III) mediated hydroalkynylation of unactivated olefins is reported. By using the characteristics of the in-situ-generated hydrogen radical from the interaction of Fe(acac)₃ and phenylsilane, hydrogen radical-triggered intramolecular 1,2-alkynyl migration was realized in this reaction, which led to the synthesis of a series of α-alkynyl ketones with moderate to good yields. Based on the experimental results and literature reports, a reasonable reaction mechanism was proposed, which involved hydrogen radical addition, 3-exo-dig cyclization (anti-Baldwin rules) and C—C bond breaking/recombination. Moreover, the reaction features good tolerance of functional groups, in which estrone-derived 1,4-enyne could be accommodated. A typical procedure for hydroalkynylation of unactivated alkenes is as follows: Fe(acac)₃ (1.2 equiv., 0.24 mmol) and NaHCO₃ (1.0 equiv., 0.2 mmol) are added to the 10-mL pressure tube. Then 1,4-enynes (1.0 equiv., 0.2 mmol) and phenylsilane (2.0 equiv., 0.4 mmol) are dissolved in 1.0 mL ethyl alcohol, respectively. Both of them are injected into this vial. The reaction system was sealed and stirred at 100 ℃ until the 1,4-enynes consumed that is determined by thin layer chromatography (TLC). After the reaction completes, the resulting mixture is extracted with EtOAc for three times, then the organic phase is concentrated and evaporated on a rotary evaporator. The residue was purified by chromatography on silica gel with petroleum ether/ethyl acetate (V∶V=75∶1) as the eluent to afford α-alkynyl ketones.

The total discharge of Chinese industrial wastewater is large, and the various organic pollutants contained in wastewater have always been a potential threat to human health. Therefore, it is necessary to develop various technologies for wastewater treatment, especially to study the degradation mechanism of organic pollutants. This paper summarizes the research methods for the degradation mechanism of various organic pollutants in wastewater, including experimental methods and computational simulations. In the experiments, spectral analysis techniques are mainly used to detect the intermediates produced during the degradation of organic pollutants, and then the degradation pathways of organic pollutants are deduced. However, due to the different experimental conditions and experimental methods, the degradation pathways of the same pollutant obtained from the different experiments are controversial. Computational simulations, based on the quantum chemical calculation, quantitative structure-activity relationship model, quantitative structure-biodegradation relationship model and statistical molecular fragmentation model, provide a new method for studying the degradation mechanism of organic pollutants. The combination of experimental methods and computational simulations will provide the foundation and guidance for exploring the degradation mechanism of organic pollutants.

A series of bimetallic MOF-74-CoMn catalysts with different metal ratios have been successfully synthesized by hydrothermal method and applied in selective catalytic reduction of NO with CO (CO-SCR). The experimental procedure for the preparation of MOF-74-CoMn catalyst is as follows:The reaction solution was a 3.28 mmol mixture of Co(NO₃)₂·6H₂O and Mn(NO₃)₂·6H₂O, 1.09 mmol 2,5-dihydroxyterephthalic acid (H₄DOBDC) and 90 mL ethanol-DMF-water. The molar ratio of mixture (Co/Mn) was 1:0, 1:1, 1:2, 1:4, 1:6, respectively. The reactant solution was ultrasonically stired for 30 min until homogeneous. Then, the mixture was transferred into a 100 mL Teflon autoclave then kept in an oven at 100℃ for 24 h. Finally, after purified with DMF and methanol, the products were dried in a vacuum oven at 80℃ for 24 h to obtain a purple MOF-74-CoMn catalyst, which were stored in vacuum or an inert atmosphere. The prepared sample is referred to as MOF-74-Co1Mnx, where x represents a molar ratio of Co to Mn is 1:x (x=0, 1, 2, 4, 6). The SCR catalytic activities were carried out in a fixed-bed flow reactor in gas stream. The experimental results show that the NO_x conversion rate of bimetallic MOF-74-CoMn catalyst is generally higher than that of single metal MOF-74-Co catalyst, and their reaction temperature window is wider. Especially, MOF-74-Co1Mn2 exhibited the highest selective catalytic reduction of NO with CO (CO-SCR) performance which is close to 100% with a temperature range from 175 to 275℃. Further, the bimetallic MOFs catalysts were characterized by X-ray powder diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), N₂ adsorption/desorption, X-ray photoelectron spectroscopy (XPS), Hydrogen-temperature programed reduction (H₂-TPR) and Infrared spectroscopy (FTIR) techniques. The results showed that the synergistic effect between Co and Mn metals could obviously promote the formation of unsaturated metal sites and oxygen vacancies, thereby promoting their catalytic reduction efficiency of selective catalytic reduction of NO with CO (CO-SCR).

Water pollution arising from ever-growing domestic sewage and industrial organic pollutants has caused severe environmental and ecological problems in many parts of the world. It is urgent to seek appropriate ways to resolve oily wastewater and organic solvent pollution. Currently, physical adsorption is considered to be one of the most important methods to eliminate the oil contaminations in water thanks to its high efficiency and low cost. However, traditional adsorbent materials, such as activated carbon, zeolite and natural fibers, often suffer from low adsorption capacities, poor adsorption selectivity and recyclability. Thus, it is still of great importance to develop new absorbent materials for the separation and removal of oils or organic pollutants from water to address environmental issues. Conjugated microporous polymers (CMPs) are a class of organic porous polymers that have attracted extensive attention thanks to their large specific surface area, good physicochemical stability and unique extended π-conjugation along the polymer skeleton. Here we report a fluorine-containing conjugated microporous polymer (F-CMP), which was synthesized via Sonogashira cross-coupling reaction from 1,3,5-trifluoro-2,4,6-triiodobenzene and 1,3,5-triethynylbenzene. As a comparison, fluorine-free conjugated microporous polymer (H-CMP) was synthesized in the same condition from 1,3,5-tribromobenzene and 1,3,5-triethynybenzene. By introducing fluorine atom into the conjugated microporous skeleton, the contact angle of F-CMP with water reaches 145°, exhibiting excellent hydrophobicity. Nitrogen adsorption/desorption isotherms of the F-CMP show a high specific surface area of 638 m²·g^-1, and the pore size distribution analysis shows the existence of both micropores and macropores. It can be obtained by adsorption experiments of oil and organic solvents that the adsorption capability of F-CMP increases significantly compared with its fluorine-free counterpart with similar structural skeleton. Due to high hydrophobicity and porous properties, F-CMP shows excellent adsorption properties towards to the removal of organic solvents and oils. The adsorption capability of F-CMP towards pump oil and chloroform can reach 40 g/g and 43 g/g, respectively. Meanwhile, F-CMP shows rapid adsorption rate and excellent adsorption recyclability. Thus, F-CMP displays promising application prospects in the field of organic pollutant adsorption and environmental remediation.

Water is the most important and essential component for the existing activities of human beings, animals and plants. It is estimated that the total amount of water on the earth is about 1.3 billion tons, but 97% of that is salty ocean water and not suitable for drinking. With the rapid growth of population, industrialization and agricultural modernization and other geological and environmental changes, the water environment is deteriorating continuously. Water pollution and water shortage are two of the most important environmental problems in the world. Consequently, water pollution has become a critical issue in recent years. Pollutants in wastewater include organic, inorganic, biological compounds. As many of them have serious toxicity and even show carcinogenic, the release of considerable amount of wastewater into environment causes damages to human being and aquatic conditions, and further leads to the shortage of water resources. Therefore, the need for wastewater treatment in a low-cost, safe and efficient way and improving the reuse efficiency of water resources have become a must. In recent years, surfactant-based separation techniques have made a great progress in industrial and analytical areas. It offers many advantages including low-energy consumption and environment protection, and has been proved efficient in the separation of many inorganic and organic pollutants. To enhance the application of surfactant-based separation techniques in wastewater treatment, it is very important to have a better understanding of the mechanisms involved in this process. The mechanism and development of surfactant-based wastewater treatment techniques, including micelle-enhanced ultrafiltration (MEUF), surfactant-modified solid phase adsorption and surfactant-based liquid-liquid phase separation are summarized. The effects of the surfactant characteristics, the chemistry of the pollutants and the solution conditions used in experiments on the extract kinetics and efficiencies are discussed. This review aims to provide reference and inspiration for researchers and promote the development of wastewater treatment technologies.

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.

Aryl halides are key building blocks in organic synthesis for the construction of valuable natural products, medicinal and agricultural chemicals via transition metal-catalyzed coupling or substitution reactions. Halogenation is one of the most fundamental and important reactions in organic synthesis. Electrochemical transition-metal-catalyzed C—H functionalization has emerged as a powerful tool for molecular synthesis with the prospect of avoiding the use of costly and toxic oxidants or reductants, thereby reducing the footprint of undesirable, toxic byproducts. The palladium-catalyzed electrochemical C—H chlorination of benzamide derivatives directed by PIP amine directing group under divided cells has been demonstrated, in which readily available inorganic halides salts serve as halogen sources. The reaction features a broad substrate scope, high functional group tolerance, and compatibility of thiophene substrates. This reaction could be conducted on a gram scale, which is important for future application. Additionally, the sequential bromination and chlorination of C(sp ²)—H bond constructs highly functionalized aromatic carboxylic acid derivatives. The typical procedure is as follows: The electrolysis was carried out in an H-type divided cell (anion-exchange membrane), with a RVC anode (10 mm×10 mm×12 mm) and a platinum cathode (10 mm×10 mm×0.2 mm). The anodic chamber was charged with Pd(OAc)₂ (5.6 mg, 0.025 mmol, 10 mol%) and benzamide derivative (0.25 mmol, 1.0 equiv.) and dissolved in DMF (10 mL). LiCl (847.8 mg, 20.0 mmol) was added in the cathodic chamber and dissolved in water (10 mL). Then the reaction mixture was electrolyzed under a constant current of 5 mA at 90 ℃ until the complete consumption of the starting material as monitored by TLC or ¹H NMR. After the reaction, EtOAc (50 mL) was added to dilute the mixture and then washed with water (20 mL×3) and then with brine (20 mL). The organic fraction was dried over Na₂SO₄ and concentrated. The resulting residue was purified by silica gel flash chromatography to give the chlorination product.

Decarboxylation of N-hydroxyphthalimide (NHPI) esters represents a powerful tool to generate carbon radicals, which has wide applications in the construction of C—C bonds and C—X bonds. Traditionally, the radical decarboxylation of NHPI esters has been enabled by transition-metal catalysis and photoredox catalysis. Recently, several visible light-mediated photosensor-free decarboxylation reactions have been reported with the use of special electron-donor systems. While notable, it’s still highly desirable to develop transition-metal-free, mild, and general methods to realize the radical decarboxylation of NHPI esters. Herein, we report 4-dimethylaminopyridine (DMAP)-boryl radical enabled Giese reaction and Barton decarboxylation of NHPI esters. The reaction starts from the generation of DMAP-boryl radical in the presence of a radical initiator, which then adds specifically to the carbonyl oxygen atom of NHPI ester 2, followed by β-fragmentation to give a nucleophilic carbon radical intermediate. Addition of the carbon radical to electron-deficient alkenes affords the Giese reaction product 4. On the other hand, hydrogen atom transfer from thiol to the nucleophilic carbon radical results in the Barton decarboxylation products 5. The reactions exhibit a broad substrate scope and excellent functional group tolerance. NHPI esters of primary, secondary, and tertiary alkyl carboxylic acids, including bio-active natural products and drugs, proceed smoothly to give the corresponding products in moderate to good yields. A variety of electron-deficient alkenes, such as vinyl esters, vinyl amides and vinyl sulphones, can be used as the Michael acceptors. A general procedure for the Giese reaction is as following: a solution of NHPI ester 2 (0.5 mmol), 4-dimethylaminopyridine-borane (0.6 mmol), AIBN (0.1 mmol) and electron- deficient alkenes 3 (0.4 mmol) in toluene (4.0 mL) was stirred at 80 ℃ for 4 h under nitrogen atmosphere. After evaporation of solvent, the crude residue was purified by flash column chromatography on silica gel (petroleum ether/ethyl acetate) to afford Giese reaction product 4. A general procedure for the Barton decarboxylation is as following: a solution of NHPI ester 2 (0.5 mmol), 4-dimethylaminopyridine-borane (0.55 mmol), TBHN (0.1 mmol) and PhSH (0.1 mmol) in benzotrifluoride (5.0 mL) was stirred at 80 ℃ for 1 h under nitrogen atmosphere. After evaporation of solvent, the crude residue was purified by flash column chromatography on silica gel (petroleum ether/ethyl acetate) to afford decarboxylative reduction product 5.

Cucurbit[8]uril (CB[8])-encapsulation-based host-guest chemistry has been utilized to construct supramolecular organic frameworks, a family of water-soluble, self-assembled periodic porous structures, from multi-armed preorganized building blocks. The tetrahedral prototype building block has been incorporated with four CH₂ units to connect the central tetraphenylmethane and appended aromatic arms. Herein we designed and prepared a new fully conjugated tetrahedral building block T-1, which possesses four N-methyl 4-(4-styrylphenyl)pyridinium (SPP) arms. The 1:2 mixture of T-1 with CB[8] in water leads to the formation of a new three-dimensional homogeneous diamondoid supramolecular organic framework SOF-r-SPP through CB[8] encapsulation for intermolecular dimers of the appended SPP units. ¹H NMR, absorption and fluorescence experiments conformed strong binding between the two components at diluted concentrations and 1:2 binding stoichiometry. Isothermal calorimetric (ITC) experiments established that the three-component (SPP)₂ÌCB[8] complexes formed between the SPP units of T-1 and CB[8] had an apparent binding constant of 5.5×10¹³ M^-2, which was 5.5×10⁴ times as high as that of the complex of a SPP control. ITC experiments also revealed that the self-assembly of SOF-r-SPP are driven both enthalpically and entropically, but the enthalpic contribution was overwhelmingly higher. Dynamic light scattering experiments revealed that within the concentration range of 0.031 mmol/L to 1.0 mmol/L of T-1, the framework possessed a hydrodynamic diameter of 41 nm to 68 nm. Molecular modelling study indicated that the new regular framework formed an aperture of 2.3 nm. Although T-1 has nearly no fluorescence, SOF-r-SPP exhibits strong fluorescence in water probably due to the encapsulation of the SPP dimers by CB[8] that suppresses the relative rotation of the aromatic rings. Adding nitrobenzene or naphthalene derivatives to the solution of SOF-r-SPP remarkably quenched the fluorescence of the framework. Among other sixteen nitro-bearing aromatic molecules, picric acid (2,4,6-trinitrophenol) exhibited the largest quenching ability. At the low concentration of 1.0 μmol/L for T-1 of SOF-r-SPP, 0.1 μmol/L of 2,4,6-tirnitrophenol could cause 16% quenching of the fluorescence of SOF-r-SPP and 0.1 mmol/L of 2,4,6-tirnitrophenol could realize nearly complete quench (>97%). Following a reported method, the limit of detection of SOF-r-SPP for picric acid was as low as 0.024 μmol/L.

Perovskite solar cells (PVSCs) have recently gained much attention for the advantages of low cost and high efficiency. Based on the different device structures, PVSCs can be simply classified into conventional and inverted categories. Compared with the inverted devices, conventional PVSCs generally exhibited higher PCE. Especially, a milestone PCE value of 24.3% was obtained in conventional PVSCs. However, the complexity and high-temperature process in device fabrication further limit their application in flexible and large-scale devices, while the inverted PVSCs can make up the shortcomings of the conventional PVSCs. Commonly, PVSCs devices contain electrodes, electron/hole transporting layers and the perovskite layer. Among the function layers, hole transporting layers (HTLs) play a crucial role in improving the photovoltaic performance of inverted PVSCs. From the materials point of view, the efficient hole transporting materials (HTMs) are mostly inorganic compounds and polymers. On the other side, taking advantages of easy modification, low price, easy preparation and homogeneity in batches, small molecular HTMs afford superior promising in fabricating efficient and stable PVSCs. However, up to date, small molecular HTMs are relatively less explored. To enrich the material species of small molecular HTMs and illustrate their superiorities in constructing stable PVSCs, in this paper, we designed and synthesized three D-π-A-π-D type small molecular HTMs based on triphenylamine (TPA) unit, namely 1-T, 1-OT and 1-OTCN. The optoelectronic properties of these molecules were modified by introducing different electron acceptor/donor groups. Afterwards, employing as dopant-free HTMs in inverted PVSCs, the three small molecules demonstrated distinguished performance. We found that introduction of electron-donating methoxy into 1-T, 1-OT exhibited increased energy levels and hole mobility. On the other hand, the energy levels of 1-OTCN were down-shifted compared to 1-OT, which was attributed from the stronger electron-withdrawing ability of dicyanovinylene group than carbonyl group. Among the devices with new HTMs, 1-OTCN based PVSCs achieved the best PCE of 16.8%, with open-circuit voltage (V_OC) of 1.09 V, short-circuit current density (J_SC) of 20.13 mA·cm^-2 and fill factor (FF) of 78%. Compared with other HTMs, the higher J_SC of 1-OTCN based PVSCs was ascribed from more efficient charge transfer and extraction in the interface of HTL/perovskite. Moreover, in contrast with the hydrophilicity of PEDOT:PSS, the hydrophobicity of 1-OTCN contributed to the satisfactory stability of PVSCs.

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.

Transition metal-catalyzed C—H activation has attracted extensive attention because of its excellent functional group tolerance and high efficiency. Among them, palladium-catalyzed reactions exhibit versatile catalytic cycles and have mild conditions compared to others. Therefore, the palladium-catalyzed C—H activation has been employed broadly as a practical strategy in synthetic chemistry during the past decade. Since the first example of palladium-catalyzed decarboxylative C—H acylation using α-oxocarboxylic acids was reported in 2008, a lot of substrates have been employed to synthesize acylated products due to the easily available α-oxocarboxylic acids as well as the importance of acylation. However, the transition metal-catalyzed C—H esterification via decarbonylation is still limited. Our group previously developed the first directed C—H esterification of methyl ketoximes and 2-phenylpyridines by using potassium oxalate monoester as the decarboxylative reagent. Encouraged by this impressive result as well as the importance of salicylate derivatives in drug discovery, herein we disclose the efficient palladium-catalyzed decarboxylative esterification of 2-aryloxpyridines. This reaction proceeds smoothly with potassium oxalate monoester, affording the desired products in moderate to good yields (50%~82%). Compared to our previous work, the electron-donating pyridinyloxy (PyO) group as the directing group and six-membered metallocycle intermediate dramatically enhance the practicability and substrate tolerance of the present method. In addition, one of the products has been chosen as the model compound to deprotect the directing group to get the valuable salicylate derivative. The present method not only provides an efficient and convenient protocol for the synthesis of ethyl salicylate derivatives, but also enriches the diversity of Pd(Ⅱ)/Pd(IV) catalytic reactions. A general procedure for the esterification of 2-aryloxypyridines 1 with potassium oxalate monoester 2 is as following:a mixture of 1 (0.5 mmol), Pd(OAc)₂ (10 mol%), K₂S₂O₈ (1.0 mmol), Ag₂CO₃ (1.0 mmol), 2 (1.0 mmol), D-CSA (0.125 mmol), and 1,4-dioxane (2.5 mL) in a 25 mL tube was heated at 80℃ for a suitable time. The reaction mixture was cooled to room temperature, and concentrated in vacuo. Purification of the residue by column chromatography on silica gel with petroleum ether and ethyl acetate as the eluent provided the desired product 3.

Apigenin-7-O-β-D-glucuronide (1) and scutellarin (scutellarein-7-O-β-D-glucuronide, 2) are two major flavone glucuronide components occurring in breviscapines, which are prepared from the traditional Chinese herb Erigeron breviscapus. These two flavone glycosides show potent anti-oxidative, anti-inflammatory and neuroprotective activities in various evaluations. Synthesis of these natural glycosides in an efficiently manner would facilitate studies on their structure activity relationships. As a persistent effort on the chemical syntheses of the diverse glycoconjugates from traditional Chinese herbs in our group, we report herein the synthesis of these two representative flavone O-glucuronides. It is known that the solubility of flavone compounds is rather low and this property would greatly hinder their glycosylation reactions. In order to increase the solubility of the flavone derivatives in the glycosylation solvents, hexanoyl and benzyl groups were selected as the permanent protecting groups for the hydroxyl groups of apigenin (7) and scutellarein (8). The construction of the phenolic O-glucuronide is known to be a difficult task, especially the glycosylation of the poorly nucleophilic 7-hydroxyl group which locates at the para-position of the flavone carbonyl group. We achieved the glycosylation of the flavone 7-OH with 2,3,4-tri-O-benzoyl-6-O-TBDPS-glucopyranosyl ortho-alkynylbenzoate (9) under the catalysis of Ph₃PAuNTf₂ (0.2 equiv., 4 ? MS, CH₂Cl₂, r.t., 5 h) in excellent yields. After that, the 6-O-TBDPS groups were removed, and the requisite glucuronides were then elaborated by oxidation of the resulting 6-OH under the conditions of DAIB/TEMPO (CH₂Cl₂/H₂O, V∶V=2∶1, r.t.) in good yields. After global deprotection, the desired products apigenin-7-O-β-D-glucuronide (1) and scutellarin (2) were obtained in overall yields of 36% (5 steps) and 7% (9 steps), respectively, from the starting flavone aglycones. Following the same strategy, four naturally occurring flavone-7-O-glycosides, namely apigetrin (3), plantaginin (4), apigenin 7-O-β-D-xylopyranoside (5) and apigenin 7-O-α-L-rhamnopyranoside (6), were smoothly synthesized in 4~7 steps with the overall yields of 61%, 13%, 58% and 61%, respectively.

Separation of photogenerated charges is one of the key steps in photocatalysis, whose efficiency largely determines the overall photocatalytic performance in water splitting. It is known that the formation of hybrid nanostructures is a promising solution to improve photocatalytic performance. However, the chemical environment difference during the synthesis of hybrid nanostructures may bring additional influencing factors to material systems. In this case, the design and synthesis of well-defined and clean samples are highly important to fundamental investigations. Integrating TiO₂ nanosheets with graphene can enhance the photocatalytic activity of TiO₂ through the effective separation of the photogenerated electrons and holes across the interface formed by C-O bonds. To investigate the influence of photogenerated charge separation on the photocatalytic performance of TiO₂/graphene composites, we modulate the separation of the photogenerated charges by controlling the size and thickness of TiO₂ nanosheets with the same chemical environment, which helps investigate its effect on the photocatalytic performance of TiO₂/graphene composites. Specifically, a series of TiO₂ nanosheets with different thickness are synthesized by controlling the amount of hydrofluoric acid and combined with graphene for photocatalytic hydrogen production. The hybrid nanostructures are formed through a simple and clean process so as to possess a reliable platform for evaluating the relationship between structural parameters and performance in photocatalytic hydrogen production. The experiment results show that the photocatalytic activity of TiO₂/rGO composites increases with the reduction in the thickness of TiO₂ nanosheets. As the thickness of TiO₂ nanosheets decreases, the migration distance of the photo-excited electrons is reduced so as to effectively suppress the recombination of the photo-excited charges. In the meanwhile, the TiO₂/graphene interface is enlarged to promote the separation of the photogenerated charges in TiO₂. As a result, the utilization efficiency of the photogenerated charges has been substantially enhanced. This work demonstrates that modulating the separation of photogenerated charges in TiO₂/graphene composites by controlling the size of TiO₂ nanosheets is an effective strategy for improving the photocatalytic performance of TiO₂/graphene composites.

The selective functionalization of unactivated sp ³ carbon-hydrogen (C—H) bond is an attractive strategy in modern organic transformation. The hydrogen atom transfer (HAT) catalysis has recently shown its advances in remotely selective activation of an inert C—H bond with great functional group compatibility, generating new carbon-carbon (C—C) bonds and carbon-heteroatom (C—O, C—N, C—X) bonds. Therefore, the remote sp ³ C—H functionalization has become an intensively investigated research area, drawing extensive attention in synthetic community. Particularly, the 1,5-hydrogen atom abstraction of nitrogen radicals, the key step of the Hoffman-L?ffler-Freytag (HLF) reaction, has been widely applied in the preparation of heterocycles. Comparing to the well-studied area of nucleophilic N-species, N-centered radical based reactions are still underdeveloped. The limited utility is partially due to the required use of hazardous radical initiators, elevated temperatures, or high-energy UV irradiation for the generation of N-radicals. Recently, visible-light photoredox catalysis has been leading efficient accesses to Nitrogen-radicals under mild conditions. The visible-light-induced nitrogen radical formation has also stimulated the development of the remote sp ³ C—H functionalization by photoredox catalysis. The classic HLF reaction requires pre-functionalization at N-center in the substrate to promote the formation of N-radical. Recently, a direct N—H single electron transfer (SET) oxidation was realized by photoredox catalysis in Knowles and Rovis’s group, generating N-radicals efficiently. The processes significantly simplified the preparation of the HLF reaction substrates and broaden the application of this classic reaction. In addition, the visible-light-induced nitrogen radical-directed reaction on modified imines provided possibilities for the remote sp ³ C—H functionalization of ketones, as ketone is the product of imine hydrolysis. Moreover, the application of chiral Lewis acid catalysis combined with visible-light photoredox catalysis enabled the asymmetric alkylation of the unactivated remote sp ³ C—H position, which achieves both regioselective and stereoselective functionalization. In conclusion, this strategy takes advantage of mild generation of N-radicals upon visible-light excitation. Subsequent 1,5-hydrogen atom transfer (1,5-HAT) and intermolecular radical coupling would realize the remote functionalization of unactivated sp ³ C—H bonds. The strategies have been successfully applied in remote C(sp ³)—H amidation, fluorination, chlorination, iodination, alkylation, vinylation, allylation, oxygenation, thioetherification, cyanation and alkynylation. In this review, we focus on visible-light-induced nitrogen radical directed functionalization of remote sp ³ C—H bonds, summarized the methodologies, and briefly reviewed their synthetic applications in pharmaceuticals and natural products.