Periodic Frustrated Lewis Pairs on Bimetallic Oxide Semiconductors for CO₂ Adsorption and Photocatalytic Conversion.

Abstract

Lewis acids (LAs) or Lewis bases (LBs) have been recognized as crucial catalytically active sites for enhancing the adsorption and conversion of inert CO₂. However, engineering of periodic frustrated Lewis pairs (PFLPs) on the surfaces of semiconductor photocatalysts presents significant challenges, and the synergistic mechanism of PFLPs in CO₂ photoreduction remains unclear. In this study, we propose a strategy that utilizes periodic oxygen vacancies to engineer dual-metallic PFLPs on bimetallic oxide semiconductor surfaces. We employ SrNb₂O_6-<i>x</i> as a model photocatalyst to elucidate the synergistic effect of PFLPs on CO₂ photoreduction. Within each FLP unit, the LA (Sr²⁺) captures an O atom from CO₂ while the LB (Nb⁴⁺) engages in an interaction with the C atom and concurrently facilitates transfer of photoinduced electrons from SrNb₂O_6-<i>x</i> to adsorbed CO₂. Thus, SrNb₂O_6-<i>x</i> with the PFLPs-enriched surface exhibits ultrahigh CO₂ adsorption and a low energy barrier for CO desorption. Under focused sunlight irradiation, SrNb₂O_6-<i>x</i> demonstrates nearly 100% selectivity in converting CO₂ to CO at a rate of 25.5 μmol g^-1 h^-1. This study presents a method for designing metal PFLPs on inorganic photocatalyst surfaces, which could contribute to the practical implementation of CO₂ photoreduction.