10 July 2022, Volume 43 Issue 7
Content
Review
Recent Progress in Heterogeneous Catalysts for the Hydrogenation of Carbon Dioxide to Methanol
ZHOU Zixuan, YANG Haiyan, SUN Yuhan, GAO Peng
2022, 43(7):  20220235.  doi:10.7503/cjcu20220235
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The utilization of fossil fuels has enabled an unprecedented era of prosperity and advancement of well- being for human society. However， the associated increase in anthropogenic carbon dioxide（CO2） emissions can negatively affect global temperatures and ocean acidity. Moreover， as a limited resource， the depletion of fossil fuels will ultimately force one to seek alternative carbon sources to maintain a sustainable development. Using green hydrogen obtained from the water electrolysis process carried out using electricity generated from renewable sources， the hydrogenation of captured CO2 to methanol not only efficiently utilizes the excess effluent CO2 from industrial gaseous waste， but also produces a clean and renewable chemical feedstock of methanol， the core of which is to develop highly efficient and stable catalysts for methanol formation. In this review， we discuss the reaction mechanism and structure-activity relationship of common heterogeneous catalysts for CO2 hydrogenation to methanol which has attracted great attention in the past decades. We also review the latest development in the design and synthesis of heterogeneous catalysts（Cu-based catalyst， noble metal catalyst and bimetallic catalysts， oxide catalyst and other novel catalysts） for methanol synthesis through the direct hydrogenation of CO2. Moreover， the opportunities and challenges in this field are also prospected.

Recent Advances in Reductive Functionalization of Carbon Dioxide with Borohydride Reagents
GUO Zhiqiang, YANG Boru, XI Chanjuan
2022, 43(7):  20220199.  doi:10.7503/cjcu20220199
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Carbon dioxide（CO2） has shown great potential as an important one-carbon（C1） source in chemical feed-stock due to its low-toxicity， abundance， availability， and recyclability. The conversion and utilization of CO2 to value-added chemical products are important part of achieving “strategies for CO2 abatement”. Due to the high kinetic and thermodynamic stability of CO2， the high selectively reductive functionalization of CO2 to the value-added chemicals simultaneously is still desirable. In recent years， great progress in activation and incorporation of CO2 into valuable chemicals has been achieved. Herein， the reductive functionalization of CO2 using borohydride reagents is summarized. It mainly describes the hydroboration of CO2 in the presence of alkali metal borohydride， ammonia borane， and organic borane.

Recent Advances on Indirect Conversion of Carbon Dioxide to Chemicals
HUANG Xiaoshun, MA Haiying, LIU Shujuan, WANG Bin, WANG Hongli, QIAN Bo, CUI Xinjiang, SHI Feng
2022, 43(7):  20220222.  doi:10.7503/cjcu20220222
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Due to the difficulty of direct carbon dioxide utilization， the indirect conversion of carbon dioxide into its derivatives such as cyclic carbonate plays one of the most important methods to realize the transformation of carbon dioxide， which has a promising application prospect. In this review， we outline recent advances in the indirect conversion of carbon dioxide to valued added chemicals via cyclic carbonate as relay molecular， focusing on the homogeneous and heterogeneous catalytic systems in the hydrogenation， alcoholysis and ammonolysis of cyclic carbonate and also investigating the reaction mechanism. Finally， we provide the challenges and opportunities in this area.

Visible-light-driven Selective Reduction of Carbon Dioxide Catalyzed by Earth-abundant Metalloporphyrin Complexes
QIU Liqi, YAO Xiangyang, HE Liangnian
2022, 43(7):  20220064.  doi:10.7503/cjcu20220064
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With the increasing energy shortage and environmental problems， the search for clean and renewable energy sources to replace fossil fuels is one of the most urgent tasks facing scientists in this century. In order to achieve our "carbon neutrality" strategic goal， the conversion of carbon dioxide（CO2） into clean fuels and chemicals using solar energy is one of the ways to achieve the sustainable development of our society. The catalyst is the core component of CO2 photoreduction technology， which can adsorb gaseous CO2 molecules and reduce them to small energy molecules such as carbon monoxide（CO）， formic acid（HCOOH）， methanol（CH3OH） and methane（CH4） under visible light irradiation. Currently， promising progress has been made in the development of novel CO2 reduction photocatalytic systems. This review summarizes the recent progress of homogeneous and heterogeneous earth-abundant metalloporphyrin-based catalysts for photocatalytic CO2 reduction， and introduces the reaction mechanism of CO2 photoreduction to CO or CH4 by homogeneous metalporphyrin catalysts， respectively， and also discusses the important applications of metalloporphyrin-based porous organic polymers with porphyrin organometallic frameworks for photocatalytic CO2 reduction. Finally， the prospect of visible-light-driven metalloporphyrin complex-catalyzed CO2 reduction is presented.

Research Progress of CO2 Hydrogenation over Pd-based Heterogeneous Catalysts
ZHOU Leilei, CHENG Haiyang, ZHAO Fengyu
2022, 43(7):  20220279.  doi:10.7503/cjcu20220279
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With the continuous increase of carbon dioxide（CO2） emissions， the impact of global warming and climate change on human life and ecological environment has become more serious. As a cheap and renewable carbon and oxygen resource， converting CO2 into high value-added chemicals is one of the shining research topics in the field of green chemistry and energy， and has received extensive attention. The Pd-based catalysts are one kind of the most promising catalysts of CO2 catalytic conversion due to its excellent hydrogenation capacity， good stability， anti- sintering and anti-poisoning properties. This paper will review the research progress of the hydrogenation of CO2 over Pd-based catalysts to synthesis small energy molecule compounds such as HCOOH， CO， CH4 and methanol. We will pay main attention to the discussion of the active sites for the adsorption/activation of CO2 molecule， strong metal- support interaction， surface and interface composition， which affect the activity and selectivity of Pd-based catalysts， as well as the catalytic mechanism over Pd-based catalysts.

Research Progress for the Role of Electrolytes in the CO2 Electrochemical Reduction
PENG Kuilin, LI Guilin, JIANG Chongyang, ZENG Shaojuan, ZHANG Xiangping
2022, 43(7):  20220238.  doi:10.7503/cjcu20220238
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CO2 emissions lead to serious greenhouse effect. However， as an important carbon resource， conversion of CO2 into useful chemicals by electrochemical CO2 reduction reaction（CO2RR） have attracted much attention due to mild reaction conditions， adjustable reaction products， and effective utilization of distributed electric energy. In the electrochemical reaction systems， electrolyte as the reaction medium can provide protons and reaction microenvironment and affect the molecule/ion transportation. Therefore， the construction of new electrolyte systems plays an important role in improving product selectivity and current density for CO2RR. This paper mainly reviews recent research progress of the role of electrolytes for the CO2RR， and summarizes emphatically the effects of ions（alkali metal ions， halide ions， etc.） in aqueous solutions and ionic liquid electrolytes on CO2 solubility， interfacial electric double layer structures（pH value， electric field effect）， and intermediate stability. This paper reveals the influence mechanism of the electrolytes on the selectivity of reaction products and current density， which provide guidance for the design of new electrolyte systems for the CO2RR.

Applications of Metal-organic Framework-based Material in Carbon Dioxide Photocatalytic Conversion
ZHAO Yingzhe, ZHANG Jianling
2022, 43(7):  20220223.  doi:10.7503/cjcu20220223
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Converting carbon dioxide（CO2） into fuels or high-additional-valued chemicals is an efficient route to decrease atmospheric CO2 concentration and mitigate green-house effect. Particularly， the photocatalytic CO2 conversion is of importance due to its mild reaction condition and low energy consumption. Metal-organic framework-based（MOF-based） materials are a kind of efficient catalyst for CO2 photocatalytic conversion owing to their unique features such as large specific surface area， good photoelectric properties and various tunability. In this article， the applications of MOF-based materials in CO2 photocatalytic reduction， cycloaddition and carboxylation in recent two years were reviewed. The advantages， limitations and future development of MOF-based materials for photocatalytic CO2 conversion reactions were discussed.

Recent Progress in Porous Framework-immobilized Molecular Catalysts for CO2 Hydrogenation to Formic Acid
DING Yang, WANG Wanhui, BAO Ming
2022, 43(7):  20220309.  doi:10.7503/cjcu20220309
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Recently， the concentration of CO2 in the atmosphere has increased dramatically， leading to the serious greenhouse effect. The conversion of CO2 as a C1 resource into fuels or fine chemicals has attracted increasing attention. The development of efficient， stable and recyclable catalysts has become vital to CO2 utilization. Among numerous CO2 hydrogenation catalysts， functional porous framework-immobilized molecular catalysts have exhibited excellent performance and become one of the research hotspots. Functional framework materials， such as porous organic polymers（POPs）， covalent organic frameworks（COFs）， and metal-organic frameworks（MOFs）， have the characteristics of large specific surface area， high thermal stability， and tunability， and play an important role in the design and synthesis of novel catalysts. This review introduces the development of porous framework POPs/COFs/MOFs-immobilized molecular catalysts and their application in catalytic hydrogenation of CO2 to formic acid.

Visible Light-driven Carboxylation with CO2
ZHANG Zhen, DENG Yu, ZHANG Qinfang, YU Dagang
2022, 43(7):  20220255.  doi:10.7503/cjcu20220255
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Carbon dioxide（CO2） is not only a well-known greenhouse gas but also one important C1 resource. It is very important to realize organic transformations with CO2 to generate high value-added compounds. Given the importance of carboxylic acid and derivatives which are widely found in natural products， medicines， daily chemicals and industrial raw materials， the synthesis of carboxylic acids with CO2 has become an important research direction. On the other hand， high temperature and other harsh conditions are always required in this field due to the low reactivity of CO2. To solve such problems， visible light is used as an clean energy source to drive the effective transformations of CO2， which has been developed significantly in last few years. This review mainly introduced and summarized the visible light-driven carboxylation with CO2 in recent years， and classified them according to types of important chemical raw materials， such as alkenes， alkynes， aldehydes and ketones， imines organo（pseudo）halides and others. The characteristics and mechanisms of each reaction were discussed. In addition， this review also provided perspective to this emerging field.

Research Progress in Electrocatalytic CO2 Reduction Reaction over Gold Clusters
YANG Dan, LIU Xu, DAI Yihu, ZHU Yan, YANG Yanhui
2022, 43(7):  20220198.  doi:10.7503/cjcu20220198
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Recently， the electrocatalytic CO2 reduction reaction（CO2RR） has attracted great attention because its wide application prospects in improving energy utilization， realizing sustainable carbon recycle and producing high value-added liquid fuels and chemicals. Atomically precise gold clusters protected by organic ligands show many advantages for electrocatalysis due to the well-defined structures. The redox potentials can be tuned by their cluster size， ligand， and composition of these clusters. Acted as ideal model catalysts， the gold clusters provide a new opportunity to explore the reaction mechanism of CO2RR at the atomic level. In this review， the research progress of CO2RR catalyzed by gold clusters is surveyed， including the effects of the charge， size， ligand and doping of gold nanoclusters on the performances of CO2RR. Particularly， the reaction mechanism of CO2RR is discussed in details. Besides， the challenges and prospects of gold nanoclusters in CO2RR are also presented.

Progress of CO2 Electroreduction to Oxalic Acid
SONG Dewen, WANG Mingwang, WANG Yani, JIAO Zhenmei, NING Hui, WU Mingbo
2022, 43(7):  20220248.  doi:10.7503/cjcu20220248
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In recent years， climate issues such as global warming caused by excessive carbon dioxide emissions have attracted wide attention around the world. And carbon emission reduction has become a common challenge to the sustainable development of human society. The conversion of carbon dioxide into high value-added chemicals by electrochemical methods is one of the ideal ways to achieve emission reduction and high value-added utilization of carbon dioxide. However， there are still many problems such as high energy consumption， low carbon dioxide conversion， poor product selectivity and difficult separation. In this paper， we take the electroreduction of carbon dioxide to oxalic acid as an example， comprehensively introduce the research progress from the aspects of reaction mechanism， catalysts， electrolyte， electrode and reactor. The key problems in the production of oxalic acid by carbon dioxide electroreduction are discussed and some valuable suggestions are put forward for the future research of carbon dioxide electroreduction to oxalic acid.

CO2-involved Electrochemical C—N Coupling into Value-added Chemicals
WANG Ruhan, JIA Shunhan, WU Limin, SUN Xiaofu, HAN Buxing
2022, 43(7):  20220395.  doi:10.7503/cjcu20220395
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CO2 is the main greenhouse gas and an important C1 resource. C—N bonds formation plays an important role in chemical industry， biosynthesis and medicine. In recent years， with the deepening of carbon neutrality and green chemistry concept， the strategy of electrochemical C—N bonds construction has attracted much attention due to its advantages of environmental benign， low carbon， simplicity and green. At the same time， continuous consumption of fossil resource results in a series of environmental and resource problems， and the green sustainable synthesis of important chemicals and fuels is attracting increasing attention. This paper focuses on the research progress of CO2-involved electrochemical C—N formation to prepare important chemicals. The electrochemical synthesis of urea， amide and amine are reviewed from the perspectives of catalytic system construction， reaction processes， and reaction mechanism. Finally， the critical challenges remaining in this research area and promising directions for future research are discussed.

Article
Synthesis and Property of CO2 Copolymer⁃based UV-curable Polymer
WANG Zhengwen, GAO Fengxiang, CAO Han, LIU Shunjie, WANG Xianhong, WANG Fosong
2022, 43(7):  20220236.  doi:10.7503/cjcu20220236
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To overcome the strong hydrophilicity of terminal hydroxyl group from low molecular weight prepolymer， high molecular weight（>40000） CO2 copolymer was synthesized through the terpolymerization of CO2， cyclohexene oxide and 4-vinyl-1，2-cyclohexene oxide using Zn-Co double metal cyanide as catalyst. The thiol-ene click chemistry was then carried out using pentaerythritol tetra（3-mercaptopropionate） as curing agent under suitable dosage of ultraviolet light irradiation. A highly transparent film could be obtained at an irradiation dose of 5.0 mJ/cm2， whose transmittance at visible light（400—750 nm） reached 97.5%， with pencil hardness of 3H and adhesion of 5B on tinplate surface by cross-cut test in ASTM D3359. It is noteworthy that the film has glass transition temperature over 110 ℃， well comparable with bisphenol A type epoxy resin， while it has the specific advantage of UV-resistance since it is aromatic ring free.

Efficient Electrocatalytic CO2 Reduction over Pyrrole Nitrogen-coordinated Single-atom Copper Catalysts
ZHAO Runyao, JI Guipeng, LIU Zhimin
2022, 43(7):  20220272.  doi:10.7503/cjcu20220272
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A series of carbon nanotube supported copper single-atom catalysts（SACu/CNT-x） was synthesized by a temperature-controlled impregnation-pyrolysis method. Extended X-ray absorption fine structure（EXAFS） analysis indicates that the single-atom copper sites were coordinated with pyridinic-N and pyrrolic-N， respectively， in the catalysts. The catalysts were applied in electrocatalytic carbon dioxide reduction. It was indicated that the catalyst with pyrrole N-coordinated copper single-atom sites showed high activity for CO2 electroreduction， affording a high CO Faradaic efficiency of 96.3% at -0.70 V（vs.RHE）. Electrochemical experiments show that the pyrrole N-coordinated copper single-atom center has a good inhibitory effect on the hydrogen evolution reaction.

Effect of Mn Promoter on CuFe-based Catalysts for CO2 Hydrogenation to Higher Alcohols
ZHANG Xinxin, XU Di, WANG Yanqiu, HONG Xinlin, LIU Guoliang, YANG Hengquan
2022, 43(7):  20220187.  doi:10.7503/cjcu20220187
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A series of Mn promoted CuFe based catalysts with different Mn contents was synthesized with the co-precipitation method. The promoting effect of Mn on CuFe based catalyst in CO2 hydrogenation to higher alcohol（HA） was studied. The catalytic results show the HA selectivity and space time yield（STY） could be effectively improved by introducing moderate Mn. The optimized catalyst denoted as 2.1MCFZ-K with 2.1%（mass fraction） Mn content exhibits the best catalytic performance with CO2 conversion of 29.4%， HA selectivity（CO-free） of 23.2%， HA space time yield of 41.1 mg·$gcat-1$·h?1， and C2+OH/ROH fraction of 96.9% at 320 ℃ and 5 MPa. X-ray diffraction（XRD）， N2 sorption experiments， X-ray photoelectron spectroscopy（XPS）， transmission electron microscopy（TEM） and H2 temperature-programmed reduction（H2-TPR） experiments reveal that Mn as a structural promoter with moderate content can reduce the particle size of Cu and promote the formation of Fe5C2 active phase， thus fabricating rich Cu-Fe5C2 active interface for HA synthesis. Overly high Mn content can block active sites， inhibiting the catalytic activity.

Efficient Electrocatalytic CO2 Reduction to CO by Tuning CdO-Carbon Black Interface
WANG Lijun, LI Xin, HONG Song, ZHAN Xinyu, WANG Di, HAO Leiduan, SUN Zhenyu
2022, 43(7):  20220317.  doi:10.7503/cjcu20220317
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Highly efficient electrochemical CO2 reduction（ECR） was realized by tuning the interface between CdO and carbon black（CB）. CdO/CB composites with different amounts of CdO and CB were prepared simply through ultrasonication. The obtained CdO/CB was characterized by a series of techniques including XRD， XPS， and TEM to reveal its composition and morphology. The ECR performance of CdO/CB composites was tested in an H-type cell. An overall ECR faradaic efficiency（FE） as high as 92.7% was achieved at -1.0 V（versus reversible hydrogen electrode） over CdO/CB with 20%（mass fraction） of CdO， in stark contrast to 69.5% over bare CdO. The highest CO FE reached 87.4%. Further control experiments and kinetic studies suggested that the enhanced catalytic activity of CdO/CB was attributed to the large contact area and interface between CdO and CB. In addition， CdO/CB exhibited stable CO FE for at least 10 h of ECR reaction. The easily accessible CdO/CB composites with tunable interface provide a feasible avenue for efficient ECR over economic electrocatalysts.

Chitosan Encapsulated CdSe QDs Assemblies for Visible Light-induced CO2 Reduction in an Aqueous Solution
XIA Wu, REN Yingyi, LIU Jing, WANG Feng
2022, 43(7):  20220192.  doi:10.7503/cjcu20220192
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MPA-CdSe@chitosan assemblies were constructed through the coordination of amino groups in chitosan to the surface Cd2+ of CdSe quantum dots（QDs）. In MPA-CdSe@chitosan assemblies， chitosan with abundant amino groups and hydrophobic polymeric structure provides a CO2-rich and hydrophobic micro-environment for QDs， thereby promoting the efficiency and selectivity of photocatalytic CO2-to-CO conversion in an aqueous solution. The photocatalytic CO formation efficiency and selectivity of the MPA-CdSe@chitosan assemblies are 169 times and 8.6 times higher， respectively， than those of MPA-CdSe QDs system without chitosan. The MPA-CdSe@chitosan assemblies exhibited good stability of producing CO with an efficiency of 73.6 mmol/g（based on QDs’ mass） and a selectivity of 51.0% after 60 h of photocatalysis.