In silico design of metal-free hydrophosphate catalysts for hydrogenation of CO2 to formate

Abstract

CO₂ reduction by H₂ using metal-free catalysts is highly challenging. Frustrated Lewis pairs (FLPs) have been considered potential metal-free catalysts for this reaction. However, most FLPs are unstable, which limits their practical applications. In this study, a class of novel metal-free catalysts composed of K_3−nH_nPO₄ (n = 0, 1, 2) and B(C₆F_5−mH_m)₃ (m = 0, 3, 5) were prepared and identified as effective catalysts for CO₂ hydrogenation to formate by density functional theory (DFT) calculations. The simulations show that the B–H bond formation is the rate-determining step (RDS). The acid/base strength and repulsive steric interactions affect the corresponding energy barrier. Therefore, the catalytic performance can be improved by choosing a suitable Lewis acid or base. Among these catalysts, the B(C₆H₅)₃–KH₂PO₄ pair, with the lowest barrier height (26.3 kcal mol⁻¹) in RDS, is suggested as a promising metal-free catalyst for CO₂ hydrogenation. This study may provide strategies for designing new LP-based metal-free catalysts.