CO2资源化利用是降低CO2排放，实现碳中和的重要方式。其中，CO2与有机化合物耦合催化转化被认为是最有效的CO2资源化路径之一。经典的热催化耦合反应由于反应条件较为剧烈，导致能耗较高且增加了碳排放，使其应用受到限制。研究表明，使用光、电催化CO2与有机化合物耦合制备高附加值产品可直接利用清洁能源，不仅实现CO2减排，促进可持续发展，还可获得碳酸酯及羧酸等高附加值化学品，创造更多经济价值。该类催化反应通常以有机分子活化为主，CO2分子活化为辅，通过光或电活化底物分子，生成高能量的活性中间体，进而克服热力学障碍。从光、电催化的优势、反应效率和反应条件等方面综述近年来光、电催化CO2与有机化合物耦合制备碳酸酯、羧酸等研究进展，详细讨论了针对不同类型有机化合物的活化策略以及各类反应的反应机理，最后提出了该领域当前仍面临的挑战并对未来进行展望。光催化多用于CO2对C—O键、C—H键的插入，主要产物分别为酯和羧酸，反应多在常温常压下进行。其中CO2与环氧化物的环加成反应研究较多，其多相催化反应已具有理想的转化率和选择性；CO2与烃类反应对合适的底物可达到理想的羧酸产率，但需均相催化剂的催化。此外，光催化反应中普遍存在的反应速率不高、可见光不易利用等问题也亟待解决。电催化多用于CO2在阴极端对C—X键、C=C键的插入，主要产物分别为羧酸和二羧酸，反应大多在常温常压下进行。其中，C—X键的还原羧化可在电极表面或溶液中存在催化剂时高效进行，但反应常生成烷烃等副产物；C=C键的还原羧化无需催化剂，但存在单羧酸和二羧酸的竞争，当底物为共轭二烯时产物更复杂。该体系研究中多采用活泼金属作为牺牲阳极，因此除提高某一产物的选择性外，未来该类型电催化反应还应考虑阳极的高效利用。

CO2 resource utilization is an important way to reduce CO2 emissions and achieve carbon neutrality. Among them, the coupled catalytic conversion of CO2 with organic compounds has been considered as an effective and promising way to the resource utilization of CO2.The classical thermal catalytic coupling reaction are limited in their application due to the high energy consumption and increased carbon emissions caused by the more violent reaction conditions. Recent research shows that photocatalytic and electrocatalytic carbon dioxide coupled with organic compounds can directly utilize clean energy, which not only realizes the CO2 emission reduction and promotes sustainable development, but also can obtain high value-added chemicals such as carbonate and carboxylic acid, thus creating more economic value. The catalysis of this kind of reaction is usually based on the activation of organic molecules, supplemented by the activation of CO2 molecules. The substrate molecules are activated by light or electricity to generate high-energy active intermediates, so that the reaction can overcome thermodynamic obstacles. In this review, we summarized the recent advances of photocatalytic and electrocatalytic carbon dioxide coupled with organic compounds from the advantages of photocatalytic and electrocatalysis, reaction efficiency and reaction conditions. The activation strategies for different types of organic compounds and the reaction mechanisms of various reactions were discussed in detail. Finally, the current challenges in this field and the future development prospects were proposed. Photocatalysis is mainly used for CO2 insertion of C—O bond and C—H bond, and the main products are esters and carboxylic acids, respectively. The reactions are mostly carried out at ambient temperature and pressure. The cycloaddition reaction of CO2 and epoxide has been widely studied, and its heterogeneous catalytic reaction has an ideal conversion rate and selectivity. The reaction of CO2 with hydrocarbons can achieve ideal carboxylic acid yield with suitable substrates, but it needs the catalysis of homogeneous catalyst. In addition, the common problems in photocatalytic reactions, such as low reaction rate and difficult use of visible light, need to be solved. Electrocatalysis is mainly used for CO2 insertion into C—X bond and C=C bond at the cathode. The main products are carboxylic acid and dicarboxylic acid, respectively. The reactions are mostly carried out at ambient temperature and pressure. Among them, C—X bond reduction carboxylation can be carried out efficiently on the electrode surface or in the presence of catalyst in solution, but the reaction often generates alkanes and other by-products. Reductive carboxylation of C=C bond does not require catalyst, but there is competition between monocarboxylic and dicarboxylic acids, and the product is more complex when the substrate is conjugated diene. In the study of this system, active metals are often used as sacrificial anodes. Therefore, in addition to improving the selectivity of a certain product, the efficient utilization of anodes should also be considered in the future study of this type of electrocatalytic reaction.

0 引言

1 太阳光驱动的CO2耦合

   1.1 CO2与醇的光催化脱水缩合

   1.2 CO2与环氧化物的光(热)催化转化

   1.3 C—H键的光催化羧化

2 电催化CO2耦合

   2.1 C—X键的还原羧化

   2.2 C=C双键的还原羧化

3 结语与展望