The reduction of CO₂ into formic acid or its conjugate base, using dihydrogen, is an attractive process. While catalysts based on noble metals have shown high turnover numbers, the use of abundant first-row metals is underdeveloped. The key steps of the reaction are CO₂ insertion into a metal hydride and regeneration of the metal hydride with H₂, along with the concomitant production of formate. For the first step, copper is known as one of the most efficient metals, as shown by the numerous copper-catalysed carboxylation reactions, but this metal has difficulties activating H₂ to achieve the second step. Here, we report a catalytic system involving a stable copper hydride that activates CO₂, working in tandem with a Lewis pair that heterolytically splits H₂. In this system, unprecedented turnover numbers for copper are obtained. Surprisingly, through a combination of stoichiometric and catalytic reactions, we show that classical Lewis pairs outperform frustrated Lewis pairs in this process.

使用二氢将CO ₂还原为甲酸或其共轭碱是一个有吸引力的过程。尽管基于贵金属的催化剂已显示出高周转率，但对丰富的第一排金属的使用却不发达。反应的关键步骤是将CO ₂插入金属氢化物中，并用H ₂再生金属氢化物，并伴随生成甲酸盐。对于第一步，铜被认为是最有效的金属之一，正如众多铜催化的羧化反应所表明的那样，但是这种金属很难活化H ₂来完成第二步。在这里，我们报告了一种催化体系，其中涉及稳定的氢化铜，可活化CO ₂，与杂化分裂H ₂的Lewis对协同工作。在该系统中，获得了空前的铜交易额。出乎意料的是，通过化学计量和催化反应的组合，我们表明在此过程中，经典的路易斯对优于沮丧的路易斯对。