Catalytic Conversion of CO2 to Formate with Renewable Hydrogen Donors: An Ambient-Pressure and H2‑Independent Strategy

Catalytic conversion of CO2 via “transfer hydrogenation” using renewable non-H2 compounds (such as biomass-derived (poly)­alcohols) to produce valuable energy-relevant chemicals, is a promising alternative strategy to the traditionally employed “hydrogenation” of CO2 with gaseous H2. However, the CO2-transfer hydrogenation has been explored exceptionally less, and limited but encouraging success has been achieved in recent time by applying high pressure (up to 50 atm) of CO2 gas. For safe and simple operation, ambient-pressure protocols are desirable, and toward this end, suitable catalysts are required. Aiming to this goal, herein we report an efficient Ir–aNHC catalyst (aNHC = an abnormal NHC ligand) to achieve ambient-pressure CO2-transfer hydrogenation catalysis for generating formate salt (HCO2–) at the turnover frequency (TOF) value of 90 h–1 in 12 h of reaction at 150 °C using glycerol as hydrogen source.

以可再生非氢化合物（如生物质基（聚）醇类）为氢源，通过转移氢化（transfer hydrogenation）路径实现二氧化碳催化转化，制备高附加值能源相关化学品，是相较于传统采用气态氢气进行二氧化碳加氢的工艺而言，极具潜力的替代策略。然而，二氧化碳转移氢化的相关研究迄今仍鲜有报道，近年来仅在采用最高50标准大气压二氧化碳的高压体系中取得了有限但令人鼓舞的进展。为实现安全简便的操作，常压反应工艺是理想选择，而开发适配的催化剂是达成该目标的关键所在。针对这一研究需求，本文报道了一种高效的铱-aNHC催化剂（aNHC = 反常氮杂环卡宾配体，abnormal NHC ligand），可用于常压二氧化碳转移氢化催化反应：以甘油为氢源，在150℃下反应12小时，转化频率（turnover frequency, TOF）可达90 h⁻¹，可生成甲酸盐（HCO₂⁻）产物。