电催化CO_(2)还原制备单一多碳产物

The greenhouse gas CO_(2)emitted in the process of fossil fuels utilization can be decontaminated through carbon capture,utilization and storage technology(CCUS),which is an important pathway to close the carbon cycle and achieve carbon neutrality[1,2].In recent years,catalyzing CO_(2)reduction into high value-added C_(2+) products with high selectivity by electrochemical method has become a promising research area.Compared to C1products(such as CO,methane,formic acid and methanol),C_(2+)products(such as ethylene,ethanol,acetic acid and n-propanol)have higher energy density and economic value.At present,the main C1products of CO_(2)reduction reaction(CO_(2)RR),such as CO and formic acid,can achieve more than 90%selectivity and meet the industrial current density requirements of 300 mA cm^(-2)[3].However,the single selectivity and current density of C_(2+)products are still facing great challenges,mainly due to the complex reaction route,slow kinetic process,low catalyst activity and lack of exploration of mechanism,which make it difficult to meet the needs of large-scale production.

Synthesis of poly(thiourethane-alt-thioester)by alternating ring-opening copolymerization of N-thiocarboxyanhydrides and episulfides

Polythiourethanes(PTU)and polythioesters(PTE)derived from renewable sources are emerging sustainable polymers for their excellent degradability and recyclability.However,P(TU-alt-TE)copolymers have been rare and challenging to synthesize.Here,we report the efficient synthesis of novel P(TU-alt-TE)copolymers via the alternating copolymerization of N-thiocarboxyanhydrides(NTA)/episufides(ES)and provide mechanistic insight into the alternating chain propagation process via density functional theory(DFT)calculation.The incorporation of ESs into traditional peptide backbone is capable of adjusting the glass transition temperature below thermal decomposition temperature,which confers better thermal processability by regulating the rigidity of the backbone and the hydrogen bond interaction among the polymer chains.Crosslinked PTUs with tailored properties are accessible by altering the feeding ratio of NTAs and(bifunctional)ESs.Moreover,the thiourethane in the backbone can endow interesting underwater adhesion properties to the materials.Considering the broad scope of NTA and ES monomers,this method is expected to provide a promising and general route to a wide range of P(TU-alt-TE)copolymers with diverse properties.

Robust Carbon-Carbon Cleavage in Lignin to Produce Phenol and Cyclohexanone

The challenge of breaking 5-5'bonds in lignin,attributed to their high bonding energy,has prompted the development of a new transformation pathway.Biphenyl,an important model compound for lignin,contains these 5-5'bonds,making it crucial to devise a strategy for their cleavage in lignin transformation.This study introduces a novel method for transforming biphenyl,involving selective hydrogenation to cyclohexylbenzene by Ni/SiO2 catalyst,followed by its oxidation to phenol and cyclohexanone through a radical mechanism.Results demonstrate that the catalysts with small particles have strong catalytic activity,while there is little difference in selectivity.The reason for the high selectivity of cyclohexylbenzene is due to the limited adsorption of cyclohexylbenzene on Ni/SiO2.This work presents a fresh approach to breaking resilient C-C bonds in lignin.

Efficient nitrate electroreduction over Mn-doped Cu catalyst via regulating N-containing intermediates adsorption configuration

The electrochemical reduction of NO_(3)^(-)to NH_(3)holds promise for economic and environmental benefits,presenting an energyefficient alternative to the traditional Haber-Bosch method.However,challenges exist due to its sluggish kinetics,multiple intermediates,and various reaction pathways.In this study,Mn-doped-Cu catalyst was synthesized and employed for electrochemical NO_(3)^(-)-to-NH_(3)conversion.The doping of Mn into Cu resulted in exceptional performance,achieving a FE of 95.8%and an NH_(3)yield rate of 0.91 mol g^(-1)h^(-1)at-0.6 V in a neutral electrolyte at low NO_(3)^(-)concentration.Detailed experimental studies and theoretical calculations revealed that the Mn dopant enhanced the kinetic rate of NO_(2)~--to-NH_(3)and induced a distinct configuration of*NO.This alteration decreased the energy barrier of*NO-to-*NOH,consequently promoting the conversion of NO_(3)^(-)-to-NH_(3).

Tuning the Surface Field by Embedding Cations into Metals to Direct the Reaction Pathway of CO_(2) Electroreduction

The creation of universal strategies to affect the reaction route of the electroreduction of CO_(2) is critical.Here,we report the first work to introduce cations into diverse metals such as Cu,Bi,In,and Sn via the electroreduction of related metallic oxides in quaternary ammonium surfactant solutions.Compared to their physical adsorption,cations embedded into the electrodes have a more pronounced impact on the electrical field,which effectively influences the adsorption state of intermediates.With the increase of surface field,the hydrogen evolution reaction and*COOH route are significantly reduced,favouring the*OCHO pathway instead.As a result,hydrogen,CO,and C_(2+)products almost completely vanish at−0.5 V versus RHE in 0.1 M Na_(2)SO_(4)in an H-type cell after enough cations are embedded into the Cu electrode,and the faradaic efficiency of formate rises from 18.0%to 99.5%simultaneously.

AI for organic and polymer synthesis

Recent years have witnessed the transformative impact from the integration of artificial intelligence with organic and polymer synthesis. This synergy offers innovative and intelligent solutions to a range of classic problems in synthetic chemistry. These exciting advancements include the prediction of molecular property, multi-step retrosynthetic pathway planning, elucidation of the structure-performance relationship of single-step transformation, establishment of the quantitative linkage between polymer structures and their functions, design and optimization of polymerization process, prediction of the structure and sequence of biological macromolecules, as well as automated and intelligent synthesis platforms. Chemists can now explore synthetic chemistry with unprecedented precision and efficiency, creating novel reactions, catalysts, and polymer materials under the datadriven paradigm. Despite these thrilling developments, the field of artificial intelligence(AI) synthetic chemistry is still in its infancy, facing challenges and limitations in terms of data openness, model interpretability, as well as software and hardware support. This review aims to provide an overview of the current progress, key challenges, and future development suggestions in the interdisciplinary field between AI and synthetic chemistry. It is hoped that this overview will offer readers a comprehensive understanding of this emerging field, inspiring and promoting further scientific research and development.

New sustainable polymers with on-demand depolymerization property

To combat the crisis of today's synthetic polymers arising from unsustainable production and disposal,it is essential for the synthetic polymer community to reshape the current polymer industry with sustainable polymers.As an emerging class of sustainable polymers,the development of chemically depolymerizable polymers(CDPs),which can undergo closed-loop depolymerization/repolymerization cycles to reproduce virgin polymers without the loss of properties from recovered monomers,offers an ideal solution to preserve finite natural resources,provides a feasible solution to the end-of-life issue of polymer waste,and thereby establishes a circular materials economy.However,two grand key challenges have been encountered in the establishment of practically useful CDPs:how to balance polymerization and depolymerization ability and how to unify conflicted depolymerizability and physical properties.Accordingly,this critical review article presents our vision for summarizing feasible strategies to overcome the above two significant challenges and the design principles for constructing an ideal CDP by highlighting selected major progress made in this rapidly expanding field.

Molecular-based conducting magnet

Molecular-based conducting magnet or magnetic conductor, is an overlap of organic conductor and molecular magnet. Due to the existence of ferromagnetism, antiferromagnetism and quantum magnetism in insulated charge-transfer salt, it becomes a common sense that magnetism is not good for conductivity. After the discovery of first molecular-based metallic ferromagnet, molecular-based conducting magnet with n-unit from organic conductor and magnetism from coordination counterion became a hot area. The metallic ferromagnet, semiconductor room-temperature ferrimagnet, metallic weak ferromagnet and supercon- ducting antiferromagnet have been discovered. The new molecular-based conducting magnet with higher conductivity and higher magnetic ordering temperature is expected.

A New Formulation of the Lindemann Mechanism of Unimolecular Reactions

A new formulation of the Lindemann mechanism of unimolecular reactions in gaseous phase is presented,without the use of steady state hypothesis. It is hereby shown that the nature of applicability of steady state hypothesis in the regime of high reactant gas pressure is different from that in the regime of low gas pressure. In the former case it is an equilibrium approximation,while in the latter case it is a highly reactive intermediate approximation in no connection with a steady state. Furthermore for the latter case it is shown that in the classical formulation of Lindemann mechanism the use of steady state hypothesis is an ad hoc assumption. A highly reactive intermediate in the sense that its concentration is very small during the whole course of reaction is a necessary condition for the applicability of very reactive intermediate approximation. When the two distinctive nature of the applicability of steady state hypothesis is mixed-up,wrong or useless conclusion may be arrived at. The only possible case of realizing a true steady state in a complex reaction is pointed out.

Roles of flanking sequences in the binding between unimolecular parallel-stranded G-quadruplexes and ligands

G-quadruplexes attract more and more attention in recent years.Numerous small molecules which can induce or stabilize the formation of G-quadruplexes have been investigated on the purpose of anticancer drug development.As a motif existed in physiological condition,flanking sequences are an important part of G-quadruplexes but the study on the impact of flanking sequences on (G-quadruplex)-ligand binding is rarely reported.In this paper,the effects of flanking sequences on binding affinity between a series of unimolecular parallel-stranded G-quadruplex sequences derived from c-myc oncogene promoter (termed as c-myc G-quadruplexes) and their ligands are discussed in detail.The results showed that the flanking sequences on c-myc G-quadruplexes play key roles in (G-quadruplex)-ligand interaction.When a c-myc G-quadruplex is bound to its ligands,the flanking sequences might form a binding cavity above the terminal G-quartet,which could provide a suitable site for ligands to dock in.Moreover,the bases on flanking sequences could interact with ligand through π-π stacking,and finally form a sandwich-stacking mode (terminal G-quartet,ligand and bases on the flanking sequence).This mode could stabilize the (G-quadruplex)-ligand complex effectively and enhance the binding affinity dramatically.However,flanking sequences are also found to exhibit steric hindrance effect which could impede the (G-quadruplex)-ligand binding.

Nitrogen-doping boosts ^(*)CO utilization and H_(2)O activation on copper for improving CO_(2) reduction to C_(2+) products

To improve the electrocatalytic transformation of carbon dioxide (CO_(2)) to multi-carbon (C_(2+)) products is of great importance.Here we developed a nitrogen-doped Cu catalyst,by which the maximum C_(2+) Faradaic efficiency can reach 72.7%in flow-cell system,with the partial current density reaching 0.62 A cm^(-2).The in situ Raman spectra demonstrate that the *CO adsorption can be strengthened on such a N-doped Cu catalyst,thus promoting the *CO utilization in the subsequent C–C coupling step.Simultaneously,the water activation can be well enhanced by N doping on Cu catalyst.Owing to the synergistic effects,the selectivity and activity for C_(2+) products over the N-deoped Cu catalyst are much improved.

Recyclable polythioesters and polydisulfides with near-equilibrium thermodynamics and dynamic covalent bonds

The accumulation of discarded petroleum-based plastics causes serious environmental crises.Currently,recyclable polymers with neutrality in thermodynamics,such as polyesters,polycarbonates,and polyolefins,have been developed as promising alternatives to traditional petroleum-based polymers.However,the chemical recycle of these polymers usually requires high energy input and expensive catalysts.Dynamic covalent bonds,such as thioester and disulfide bonds,have emerged as building blocks for constructing recyclable polymers that can be rapidly degraded/recycled under mild conditions.In this review,we introduce representative studies on recyclable polythioesters and polydisulfides with respect to their synthetic strategies,thermodynamic manipulation,physicochemical properties,and preliminary applications.We also highlight the important role of kinetic factors played in the design of recyclable polymers.Finally,major challenges,perspectives,and future opportunities in the synthesis and applications of polythioesters/polydisulfides are discussed.

Structure-Property Relationship Analysis of D-Penicillamine-Derivedβ-Polythioesters with Varied Alkyl Side Groups

The ring-opening polymerization of heterocyclic monomers and the reversed ring-closing depolymerization of corresponding polymers with neutral thermodynamics are broadly explored to establish a circular economy of next-generation plastics.Polythioesters(PTEs),analogues of polyesters,are emerging materials for this purpose due to their high refractive index,high crystallinity,dynamic property and responsiveness.In this work,we synthesize and polymerize a series of D-penicillamine-derivedβ-thiolactones(NRPenTL)with varied side chain alkyl groups,and study the structure-property relationship of the resulting polymers.The obtained PTEs exhibit tunable glass transition temperature in a wide range of 130–50℃,and melting temperature of 90–105℃.In addition,copolymerizations of monomers with different side chains are effective in modulating material properties.The obtained homo and copolymers can be fully depolymerized to recycle monomers.This work provides a robust molecular platform and detailed structure-property relationship of PTEs with potential of achieving sustainable plastics.

Single Molecule Imaging with Liquid Phase Electron Microscopy

Few single-molecule experiments have enabled the direct imaging of functional biomacromolecules in real-time in their native liquid environments,resolving their conformational adaptations,transient interactions,and intermediate states.Liquid phase electron microscopy(LP-EM),due to its unique combination of spatial and temporal resolution,has shown to be a promising tool.Recent experiments have enabled successful imaging of intact structures of organic molecules and biological systems with an ordinary electron microscope.Adapting image processing methods and quantitative data analysis from single particle experiments based on the optical microscope,quantifying motion and relaxation of these interacting molecules allows the experimental observations of pathways,to test theoretical predictions,and discovery of new mechanisms.Combining LP-EM with tomography,fluorescence,and mass spectroscopy allows for probing multi-dimensional structural and dynamic information.Challenges remain in obtaining high-quality data in large quantities,which can be improved by developing new liquid cell platforms and machine learning-based data analysis.

Conversion of polyethylene to gasoline:Influence of porosity and acidity of zeolites

Plastic waste is causing serious environmental problems. Developing efficient, cheap and stable catalytic routes to convert plastic waste into valuable products is of great importance for sustainable development, but remains to be a challenging task. Zeolites are cheap and stable, but they are usually not efficient for plastic conversion at a low temperature. Herein a series of microporous and mesoporous zeolites were used to study the influence of porosity and acidity of zeolite on catalytic activity for plastics conversion. It was observed that H-Beta zeolite was an efficient catalyst for cracking high-density polyethylene to gasoline at 240℃, and the products were almost C_(4)–C_(12) alkanes. The effect of porosity and acidity on catalytic performance of zeolites was evaluated, which clearly visualized the good performance of H-Beta due to high surface area, large channel system, large amount accessible acidic sites. This study provides very useful information for designing zeolites for efficient conversion of plastics.

An immunomodulatory polypeptide hydrogel for osteochondral defect repair

Osteochondral injury is a common and frequent orthopedic disease that can lead to more serious degenerative joint disease.Tissue engineering is a promising modality for osteochondral repair,but the implanted scaffolds are often immunogenic and can induce unwanted foreign body reaction(FBR).Here,we prepare a polypept(o)ide-based PAA-RGD hydrogel using a novel thiol/thioester dual-functionalized hyperbranched polypeptide P(EG3Glu-co-Cys)and maleimide-functionalized polysarcosine under biologically benign conditions.The PAA-RGD hydrogel shows suitable biodegradability,excellent biocompatibility,and low immunogenicity,which together lead to optimal performance for osteochondral repair in New Zealand white rabbits even at the early stage of implantation.Further in vitro and in vivo mechanistic studies corroborate the immunomodulatory role of the PAA-RGD hydrogel,which induces minimum FBR responses and a high level of polarization of macrophages into the immunosuppressive M2 subtypes.These findings demonstrate the promising potential of the PAA-RGD hydrogel for osteochondral regeneration and highlight the importance of immunomodulation.The results may inspire the development of PAA-based materials for not only osteochondral defect repair but also various other tissue engineering and bio-implantation applications.

无机盐诱导的预相分离区溶液中电沉积制备高效电还原CO_(2)电极材料

电化学反应中电极的制备策略会极大地影响电极的整体性能,进而决定电催化反应的效率.本文首次报道了过渡金属盐能够诱导离子液体/乙醇两相混合物转变为单相溶液,并在相界附近观察到溶液物理化学性质和聚集体尺寸随组成急剧变化的预相分离区.预相分离区兼具均相和非均相特性,能有效地控制金属颗粒的电沉积动力学,使得金属纳米颗粒可以沿碳纸(CP)基底的纤维均匀沉积.制备的Zn/CP电极对离子液体电解液具有超润湿性,其电催化CO_(2)还原制备CO的电流密度可达340mA cm^(-2),且CO的法拉第效率为97.4%,远高于H型电解池中的文献报道结果.该工作展现了预相分离区溶液在材料合成中的应用潜力,为预相分离区的应用打开了新思路.

Trinuclear Dy(III)Single-Molecule Magnets with Two-Step Relaxation

The reaction of DyCl_(3)·6H_(2)O with a rigid diacylhydrazone ligand(H_(2)L)afforded a trinuclear precursor[Dy_(3)L_(2)Cl_(3)(H_(2)O)_(2)(CH_(3)OH)]Cl_(2)·3CH_(3)OH(1).The replacement of the Cl-ions and the coordinating solvents by the aryloxides ligands(Lx)-yields three trinuclear complexes[Dy_(3)L_(2)(Lx)_(5)]·nsol(x=1,2-naphthol(2);x=2,7-hydroxycoumarin(3);and x=3,phenol(4)).In complexes 2-4,two end Dy^(3+)centers adopt almost identical N_(4)O_(4) coordination sphere of D6h geometry while the central one adopts N_(4)O_(5) coordination sphere in Cs geometry.Magnetic measurements reveal weak antiferromagnetic interactions in the hydrated samples 2e-4e and two-step slow relaxation process under zero dc field with effective energy barriers Ueff of 439 and 91 K,353 and 40 K,466 and 89 K for SR and FR in 2e-4e,respectively.Such dynamic magnetic behaviour for 4 persists in the magnetically diluted sample of 4@Y.Complex 4 possesses the short Dy-O_(aryloxide) bond distance of 2.055(18)Å,and the largest Ueff among the reported linear trinuclear dysprosium complexes.Moreover,the functionalized aryloxides ligands(Lx)-show photoluminescence via intramolecular energy transfer,making 2e-4e luminescent Dy^(3+)SMMs with high energy barriers.

Chitosan-mediated synthesis of mesoporous α-Fe_(2)O_(3)nanoparticles and their applications in catalyzing selective oxidation of cyclohexane

This paper reports the chitosan-mediated synthesis of porous hematite nanoparticles with FeCl3 as the precursor via a hydrothermal approach at 160℃.A series of porous chitosan/iron oxide hybrid nanoparticles were obtained via changing the ratio of chitosan to FeCl3,FeCl3 concentration and pH value of the reaction solution,and producing porous iron oxide nanoparticles after calcination.The as-prepared samples were characterized by means of X-ray diffraction,transmission electron microscopy,thermal gravimetric analysis,Fourier transform infrared,and N2 sorption.The particle sizes of these metal oxides were less than 100 nm,and the pore sizes were in the range of 2-16 nm.It was demonstrated that chitosan played a key role in the formation of the porous structures.The resultant α-Fe2O3 nanoparticles were used as the support to immobilize Au or Pd nanoparticles,producing Au/α-Fe2O3 or Pd/α-Fe2O3 nanoparticles.The as-prepared α-Fe2O3 nanocatalyst exhibited high selectivity towards cyclohexanone and cyclohexanol for catalyzing cyclohexane oxidation with O2 at 150℃.

Determination of interface (surface) dilatation rheological properties

This note establishes a new method that can measure interface dilatation elastic module (ε) and dilatation viscosity (ηd) of all surfactants based on the surface pressure relaxation process. The wide applicability was proved with the stability of foam as an example.