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.

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.

During the past decades, extensive investigations on metal-organic frameworks (MOFs) with ultrahigh surface area for gas adsorption and separation have been reported. With the increasing number of possible MOFs, it has been a great challenge to discover high-performing MOFs of interest from numerous structures. High-throughput computational screening (HTCS) is a powerful tool to accelerate the development of MOFs for application of interest and explores the quantitative structure-property relationship (QSPR) to facilitate the rational design of top-performing MOFs. In this review, we summarize the MOF databases used for HTCS, mainly including MOFs collected from experimentally synthesized MOFs (i.e. eMOFs), and the hypothetical MOFs constructed by computer-aided tools (i.e. hMOFs). Moreover, there are currently two important screening strategies, molecular simulation and machine learning-based HTCS. A vast majority of HTCS have been performed by molecular simulations including grand canonical Monte Carlo (GCMC) and molecular dynamics (MD) simulations, in which the accuracy of force field parameters play a criticl role in the reliability of HTCS. GCMC is able to predict the adsorption performance of MOFs such as adsorption capacity, selectivity and heat of adsorption, whereas MD is commonly used to estimate the dynamic property of adsorbates, e.g. diffusion coefficient and permeability. Additionally, lattice GCMC and classical density functional theory (cDFT) are also highlighted for computational screening of MOFs in this review. Machine learning consisting of various algorithms is a recently developed strategy with high efficiency and low computational cost, which is a more powerful and promising technique in future. At last, the investigations on the utilization of HTCS in CH₄ storage, H₂ storage, CO₂ capture and gas separation were outlined. By reviewing the recent research progress in HTCS, we pointed out the current challenges and opportunities for the furture development of HTCS for MOFs, which will be the major engine for the commercialization of MOFs in various applications of interests.

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.

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.

Recently, a digestive ripening process at nanoscale has been widely used to prepare monodisperse nanoparticles (NPs), especially for sub-10 nm small NPs, with significant advantages such as the very narrow size distribution of the obtained nanoparticles, the versatile applications for various nanoparticles and the simple operation process. However, no Chinese references are reported on digestive ripening process till now, which may limit the cognition and utility of digestive ripening method for some domestic scientists. Thus, this review starts from the discovery of the phenomenon and the proposal of mechanism for digestive ripening at nanoscale, to the analysis of influence factors including the precursor in the precipitation reaction, the digestive ripening reagent, heating treatment temperature and processing time, solvent media and so on. Then, theoretical hypothesis and the derived results are introduced based on the charged surface, the curvature effect, the interaction between NP surface and attached ligand layer, the diffusion effect and the competing reaction balance in the digestive ripening process. Subsequently, the important applications of digestive ripening method in the preparation of monodisperse nanomaterials of metal NPs, alloy NPs, quantum dots of metal oxide and metal chalcogenide, and other NPs are discussed, the obtained small metal or alloy NPs show a perfect sphere shape and a very narrow size distribution (relative standard deviation less than ±5%). Finally, the broad perspectives are proposed in the NP assembly for optical, electric and magnetic nanodevices, and the heterogeneous catalysis of monodisperse metal, alloy and semiconducotr NPs via the digestive ripening method.

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 special wettability of superhydrophobic surface usually has high contact angles (CA>150°) and low contact angle hysteresis (CAH<5°), which has been exploited for many potential applications. It is well known that wettability is mainly determined by micro/nano structure and surface composition, and various types of natural superhydrophobic surface could exhibit different wetting states, showing different wetting properties, such as low adhesive lotus leaf; the anisotropic superhydrophobic rice leaf; high adhesive rose petal. Therefore, the relationship between the wetting state and the surface structure should have a deeper understanding, especially in the design preliminary stage. The "droplet-superhydrophobic surface" system is taken as the research objects, four stable wetting state expressions are analyzed based on the principle of minimum energy. Wetting state transitions are studied on superhydrophobic surface coverd with micro/nano structured pillars of different distributions. The calculation formula of intrinsic contact angle is derived and the intrinsic contact angle of common materials is investigated. Based on the four wetting state of apparent contact angle equations, wetting diagrams were drew for investigating the wetting behavior, which include "one point, three lines, six areas, four state". The influence of the relative structure spacing and relative structure height on the wetting state is analyzed. It is found that the larger relative structure height, the smaller relative structure spacing, which can reduce the critical parameters of the transition state of the infiltration state, thereby expanding the range of the superhydrophobic surface, the more design options are available. It is also beneficial to the stability of the superhydrophobic surface, but should be controlled within certain scales because of mechanical stability. The simulation results accurately reflect the wetting state with the changes of the relative structure spacing and relative structure height. Finally, the general design of the superhydrophobic surface is refined. The results can provide theoretical guidance and technical fundament for the design of superhydrophobic surfaces.

The worldwide climate issues such as the global warming and the sea level rising are becoming serious. In order to relieve the stress of environment, a lot of attempts have been made to reduce the emission of CO₂, which is the main component of greenhouse gases. CO₂ capture and conversion (C3) is an emerging technology, which directly converts the captured CO₂ into high value-added compounds or fuels such as formic acid, methanol and methane. Porphyrin metal-organic frameworks (PMOFs) are based on porphyrin or metalloporphyrin ligands and metal nodes. The combination of excellent thermal/chemical stability, strong absorption of visible light and long lifetime of excited state, and high CO₂ capture capacity paves the way for the applications of PMOFs in C3. In this review, we have firstly introduced the synthesis strategies of PMOFs, which are guided by framework topology, pillar-layer and metal-organic cage (MOC). With the good control of the pore sizes and thermal/chemical stability, the catalytic performances of PMOFs can be easily tuned:PMOFs that are prepared via the pillar-layer and MOC strategies are of relatively lower stability, and the ones that are guided by framework topology are of higher stability. Next, we have classified the types of PMOFs according to the secondary building units (SBUs). There are four types of PMOFs, and the SBUs include (1) the low-valence metal ions such as Cu²⁺ and Cd²⁺; (2) the paddle-wheel M₂(COO)₄ (M=Cu²⁺, Zn²⁺) units; (3) the infinite metal (such as Al³⁺, Ga³⁺ and In³⁺) oxide chains; (4) the hard metal (such as Cr³⁺, Fe³⁺, Ti⁴⁺, Zr⁴⁺, Hf⁴⁺, and rare earth metals) oxide clusters. The structure characters and stability have been described afterwards. The coordination bonds in the first and second types of SBUs are relatively weak. For comparison, most of the PMOFs based on the infinite metal oxide chains and hard metal oxide cluster exhibit high thermal/chemical stabilities, which could be used for practical applications towards C3. Then, we have summarized the recent works about applications of PMOFs in C3, which are divided into four parts, including the selective capture of CO₂, organic transformations with CO₂, CO₂ photoreduction and CO₂ electroreduction. Selective capture of CO₂ from a mixture of gases is one of the most important applications, considering that less energy and lower temperatures/pressures are required. Through the catalytic cycloaddition reaction of CO₂ and epoxides, the important products of cyclic carbonates can be produced. Some of the catalytic reactions can be carried out at 0.1 MPa and room temperature with high yields. With the assistance of environmentally friendly visible light, CO₂ can be photoreduced into fuels such as formate ion, methanol and methane. In addition, two typical examples of CO₂ electroreduction have been discussed in this review. Through the process of photoreduction and electroreduction, clean energies such as solar light and electricity can be employed to help transfer the green gas CO₂ into fuels. At the end, we have discussed the merits and challenges of PMOFs in the applications of C3. Selective adsorption of CO₂ from other gases, especially NO_x, SO_x and other flue gases, is highly required. The efficiency of the catalytic cycloaddition reaction should be further improved, especially cutting down the reaction time. Reaction efficiency and product selectivity of photoreduction and electroreduction should be improved. Photoelectrocatalytic reduction of CO₂, which combines both advantages of photoreduction and electroreduction, should be a hot topic in the future. The ideal system should include both a photoanode for water oxidation and a photocathode for CO₂ reduction that are linked by a wire without external applied bias, achieving the dream of artificial photosynthesis.

In recent years, the use of gas therapy has been more and more concerned by researchers in biomedical applications. Carbon monoxide (CO) is a diatomic gas messenger molecule with the function of transmitting intercellular information and regulating cellular signals. CO is found to play an extremely important physiological role in multiple systems, including cardiovascular system, nervous system, immune system, endocrine system and respiratory system, cancer therapy, coagulation and fibrinolysis system, organ transplantation and preservation, and so on. The biological functions of carbon monoxide molecule greatly depend on the its concentration, position, and duration. However, the existing carbon monoxide donors including Mn₂(CO)₁₀, Ru₂Cl₄(CO)₆, Ru(CO)₃Cl(glycinato), CORM-F, CORM-A1 have some disadvantages, such as poor stability, difficulties in dose control, lack of targeting, potential toxic and side effects on normal cells and tissues, which limited their further applications. How to control the concentration of carbon monoxide in the specific region has always been a big challenge in the field of biomedical applications. With the rapid development of nanoscience and technology, researchers have constructed a series of multifunctional carbon monoxide releasing nanomaterials, provided a new idea for CO controlled release, and applied them in the field of biomedicine. In this paper, several kinds of endogenous/exogenous stimulus-responsive CO releasing nanomaterials with the unique advantages are introduced based on the stimuli source. Then, the applications of these controlled CO releasing nanomaterials in biomedical fields, such as inhibiting inflammation, anti-bacte- rial and cancer therapy, are summarized. Finally, the challenges and prospects of CO releasing nanomaterials are discussed.

As an ultra-wide bandgap insulating material, boron nitride has attracted intense interest due to its high thermal conductivity, high chemical and thermal stability as well as their applications in thermal interface materials, photo/electro-catalysis, and energy storage. As for the low dimensional boron nitride nanostructures, e.g., nanosheets, nanotubes, nanorods, nanowires, nanospheres, and quantum dots, the high thermal conductivity (600 W/mK) and the ultra-large bandgap (5~6 eV) make them the promising candidate for thermal conductive composites, thermoelectric materials and electronic packaging materials, which gives rise to the hot research topic on the synthesis and properties of the boron nitride nanostructures. In this review, the recent advances in the hydrothermal synthesis of boron nitride nanostructures will be fully discussed, and the remarks on the issues need to be addressed, the comprehensive understanding of the mechanism and the new approaches for the hydrothermal synthesis will be proposed in the end.

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.

Carbonate radical, nitrate radical, phosphate radical and sulfate radical are all important intermediates of chemical reactions with oxidizing ability. They have a significant effect on the transfer of pollutants in natural environment. In this review, the redox potential, modes of production, detection methods of these radicals and the mechanisms of their reactions with organic compounds are introduced. It can be found that:these four radicals have different reaction rates with organic compounds because of their various redox potential; Carbonate radical is not a scavenger of hydroxyl radical. For some easily oxidized compounds, carbonate radical shows higher oxidizing ability than hydroxyl radical; Hydroxyl radicals can be converted into other four types of radicals. Meanwhile, these four types of radicals react with organic matters by electron transfer, hydrogen abstraction and addition, which is basically consistent with hydroxyl radicals. It can be predicted that the mechanism of organic compounds degradation by these four types of free radicals is similar with that of hydroxyl radicals. In the future, it is necessary to study the mutual conversion principles between these free radicals and hydroxyl radicals and the degradation mechanism of these radicals when reacting with some representative organic compounds.

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.

Carbohydrates, along with proteins and nucleic acids are known as basic life substances, which not only are the energy source and structure material, but also play an extremely important role in many biochemical processes, such as molecules recognition, information transformation in cells, interactions in immune response, differentiation and apoptosis of cells, etc. Compared to proteins and nucleic acids, the synthesis of oligosaccharides in chemical or enzymatic ways is more difficult, due to their diversified and complicated structures. Recently photo especially visible light promoted organic synthesis has become one of the fastest growing fields in organic chemistry attributed to its environmental friendliness, easy availability and low cost. This chemistry has also been applied to the photo-mediated glycosylation reactions by using various light sources (ultraviolet, visible light), photosensitizers (or photocatalysts), and additives (oxidants, reductants etc.), which provides milder and more effective ways for oligosaccharide assembly. To help chemists understand this field, we briefly reviewed recent advances and potential applications of photo-mediated glycosylation reactions according to their types (e.g. light sources, photosensitizers). In this review, we also detailly described the mechanisms and highlighted the advantages and limitations of these reactions. In addition, the further prospects of this area are proposed.

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.

Hypervalent iodine chemistry has arose as an important field in organic chemistry in the past decades. Hypervalent iodine compounds, with reactivities similarly to transition metals in many different types of transformations, have attracted broad interests in organic community due to their practical advantages in the mild conditions, low costs, environmental benign and low toxicity. Great progresses have been made in this field. Chiral hypervalent iodine reagents or precursors have also been developed and utilized in a variety of asymmetric reactions in a stoichiometric or catalytic way. Important advances have been witnessed in the field of chiral hypervalent iodine chemistry in recent years. However, great limitations still exist. In this review, we have made a summary of different types of chiral hypervalent iodine reagents and precursors according to the characteristics of these compounds and the timeline. It may be helpful for the researchers to better understand the development and limitations of chiral hypervalent iodine chemistry.

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.

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.

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.

Isocyanates is a widely-used chemical in many manufacturing industries, such as polymer industry, pharmaceutical production and production of a variety of agricultural chemicals. However, it is harmful to human health due to the volatility. Therefore, it is necessary to develop methods to detect isocyanates quickly and conveniently, especially to gaseous isocyanates. In this work, a novel fluorescent probe, N-buty-4-hydroxy-1,8naphthalimide, was developed for detection of isocyanates. This fluorescence probe can be synthesized by a simple three-steps synthetic route, and the overall yield of the whole synthesizing process reached 75%. In the absence of isocyanate, the probe solution displays an emission centering at 596 nm when excited at 370 nm, which is yellow to the naked eye. Once isocyanate is added, the fluorescence of solution changes from yellow to blue, and the process finishes in 4 min. The detecting limit of this probe to isocyanates is calculated to be 112 nmol·L^-1. It is also proved that this probe possesses excellent selectivity for isocyanate and distinct anti-interference to common organic volatilized compounds. In addition, the reaction mechanism between the probe and isocyanate were proved by HPLC, NMR and ESI-MASS. Results show that the hydroxy group on the 4th position of naphthalene ring of probe reacts with isocyanate group (-NCO) of isocyanate, and resulting in carbamates, which alter 4th substituent group of probe molecule and lead to change of fluorescence. In order to detect the gaseous isocyanates directly, test paper are developed based on N-buty-4-hydroxy-1,8naphthalimide. When the test paper exposed to isocyanates vapor, the yellow fluorescence fade away gradually and a blue fluorescence appear in 6 min. And the test paper possesses excellent selectivity for gaseous isocyanate and distinct anti-interference to common VOCs. In conclusion, this strategy is an efficient way to detect gaseous isocyanates, and it may provide a referable approach for directly monitoring the volatile organic compounds in air.

Immunotherapy for cancer is a method to treat cancer by using the body's own immune system. Programmed death receptor 1 (PD-1) is one of the checkpoints in the immunotherapy. The signal pathway PD-1 (programmed death receptor 1)/PD-L1 (ligand of PD-1) is closely related to the immune escape of the cancer cells. The inhibitor drugs for PD-1 checkpoint, essentially the monoclonal antibodies of PD-1 or PD-L1 which is essentially the immune checkpoints inhibitors could block the PD-1/PD-L1 pathway and reactivate T-cells to kill cancer cells, and as a result, the immunotherapy for cancer is realized. In order to study the binding process of PD-1 drugs and PD-1 antigen in vivo, in this work, solid-state nanopore as a single molecule method is used to detect the binding of PD-1 antibody and antigen. The PD-1 antibody as well as antigen is driven though the same nanopore under the same experimental condition by the external electric field. Since the antibody's block is about 0.01297 while the antigen's block is 0.00404, the PD-1 antibody is distinguished with the PD-1 antigen according to the theoretical formula. Driving the PD-1 antigen though the nanopore modified by PD-1 antibody (a series of experiments are conducted for characterization) under the same temperature and buffer concentration, the antibody-antigen complexes are detected and distinguished with PD-1 protein and its antibody through the relative current drop analysis and the current drop achieved before. The results suggest that the antibody and antigen have a specific binding (the smaller peak represents the free PD-1 antibody and antigen) and the binding process can be detected by nano-sensors. So the nanopore is able to distinguish the antibody, the antigen and the complexes without any labling. And in the future, the nanopore technology may be a rapid and label-free way for patients and doctors to evaluate the drugs' efficiency.

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.

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.

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.

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.

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.

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.

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.

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.

Surface Enhanced Raman Spectroscopy (SERS) has been developed as one of powerful tools for monitoring the organic reaction due to its extremely high sensitivity. Moreover, SERS provided the abundant fingerprint spectroscopic information for the structure analysis, and it could be integrated with other techniques to achieve the on-line detection. Microfluidic technology, due to its significant role in the miniaturization, integration and portability of instrument, exhibits the promising application in biomedicine, high throughput drug screening, the environment monitoring and protection. In recent years, the microfluidic chip as one of the modern technology for analyzing various substances at the same time has been rapidly developed. Compared with the conventional technique, it has the significant advantage and convenience, such as low reagent consumption, short reaction time, high reaction efficiency and so on. Herein, the microfluidic chip was employed as the microreactor for organic reaction with the ultralow dosage, and the SERS detection was integrated into the microreactor to realize the continuous monitoring on the substrates and products. The magnetic core-shell nanoparticles Fe₃O₄@Ag acted as the SERS substrate with reasonable magnetism and SERS activities, and it demonstrated that the magnetic nanoparticles was flowed in the microchannel of microfluidic chip and was enriched by the external magnetic field. The introduction of magnetic nanoparticles is beneficial to improve the detection sensitivity by the magnetic aggregation and to reach the continuous SERS detection by applying and retracting external magnetic field. At the same time, it exhibited the significant advantages of low amount of reactants, high efficiency and easy to realize on-line detection and high throughput screening in organic synthesis. The micro-synthesis of α-phenylethanol and the real-time monitoring of SERS are performed by the alternative enrichment and de-enrichment of magnetic nanoparticles in the present case. By changing the flow rate of reactants in the channel of microfluidic chip, different concentrations of reactants and products were obtained in a certain duration. The influence of the spectral features from the reactants was eliminated by differential spectrum technique, and the distinctive SERS spectrum of α-phenylethanol was presented accordingly. It demonstrated that the integration of microfluidic chip and SERS technique could be developed as a powerful tool for on-line monitoring organic reactions and exhibits the promising application in high throughput screening of organic chemical reactions.

Cyclic di-AMP (c-di-AMP) is a ubiquitous second messenger in prokaryotic cells. c-di-AMP can not only effectively regulate various physiological processes such as cell growth, ion transport and cell wall metabolism balance, but also trigger type I interferon response to inspire the body's immune response. Nanopore-based single molecule detection technology is an emerging single molecule detection method which is currently applied to various fields since it has many advantages such as high speed, label-free, high sensitivity and low cost. Aerolysin is a robust biological nanopore with high temporal resolution and high current resolution, which has achieved single oligonucleotide detection, polysaccharide analysis and the studies of enzymolysis kinetics. Aerolysin nanopore is negatively-charged protein nanopore which has numerous negatively charged amino acid residues around its cis entrances. The electrostatic repulsion between the negatively charged c-di-AMP and negatively charged amino acid residues around the cis entrances prevents c-di-AMP entering the nanopore. In this study, 1.0 mol/L LiCl was used as electrolyte solution to facilitate aerolysin analysis of single c-di-AMP molecule. Each event can be characterized by two parameters, the current blockade, I/I₀, and the blockade time, τ_off. The blockades are classified into two populations as PI and PII. The PI events are assigned to c-di-AMP that bump into the pore and then diffuse away. PII events are assigned to traversing of c-di-AMP through the nanopore. Compared with potassium ions, lithium ion can be more effectively to associate with the negative charges on the aerolysin nanopore surface and reduce the electrostatic repulsion between the c-di-AMP molecule and the Aerolysin. The results showed that number of PI events in per minute was significantly increased in 1.0 mol/L LiCl. The number of PI events in per minute in LiCl is 30 times than that in KCl at 90 mV. Hence, Aerolysin nanopore can be used as an ultrasensitive single molecule sensor for cyclic dinucleotides.

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.

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.

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.

A novel yellow thermally activated delayed fluorescence emitter pPBPXZ was successfully synthesized using phenoxazine as electron-donor and pyrimidine as electron-acceptor by Buchwald-Hartwig and Suzuki coupling reactions. Density functional theory calculations show that pPBPXZ has highly twisted structure with the dihedrals of nearly 90° between phenoxazine and pyrimidine units, while the dihedrals between benzene ring and adjacent pyrimidine rings are almost 0°. The highest occupied molecular orbital (HOMO) is mainly confined on two phenoxazine segments, the lowest unoccupied molecular orbital (LUMO) is mainly located on the central pyrimidine and benzene segments, and there is only a slight overlap between HOMO and LUMO. Cyclic voltammetry investigation show pPBPXZ has reversible redox process, and the HOMO and LUMO energy levels were estimated to be -5.43 eV and -3.23 eV, respectively, from the onsets of oxidation and reduction curves. In diluted toluene solution, pPBPXZ exhibits the absorption band assigned to intramolecular charge-transfer transition and yellow fluorescence with a structureless emission peak at 535 nm. From the onsets of the fluorescence and phosphorescence spectra of pPBPXZ in 2Me-THF at 77 K, the lowest singlet (S₁) and the lowest triplet (T₁) energy levels are calculated to be 2.57 eV and 2.48 eV, respectively, and thus △E_ST is only 0.09 eV. The doped electroluminescence devices using pPBPXZ as guest emitter were prepared by vacuum evaporation method. These devices with doping ratios (w) of 6%, 11%, 16% and 23% show yellow emission at 552~560 nm and low turn-on voltages of 3.1~3.3 V. The device with a doping ratio of 11% exhibits the highest maximum forward-viewing efficiencies of a maximum current efficiency of 49.9 cd/A, a maximum power efficiency of 49.0 lm/W and a maximum external quantum efficiency of 15.7% without any light out-coupling enhancement. Particularly, the efficiencies of these devices are not sensitive to the doping ratios of pPBPXZ, which would benefit the further practical application.

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.

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).