Additive-free CO2 hydrogenation to pure formic acid solution via amine-modified Pd catalyst at room temperature

Direct conversion of CO2 into pure formic acid (FA) solution in the absence of base additives is of great significance, but is challenging due to thermodynamic limitations. Here, we have synthesized ultrafine Pd nano-catalysts modified with three kinds of amine groups, including a primary amine (PA), secondary amine (SA) and tertiary amine (TA), which realized the efficient hydrogenation of CO2 to pure FA in water at room temperature for the first time. Comprehensive characterizations reveal that all the amine groups are beneficial to the formation of ultrafine and uniform Pd nanoclusters (