Tailoring Surface Frustrated Lewis Pairs of In2O3−x(OH)y for Gas‐Phase Heterogeneous Photocatalytic Reduction of CO2 by Isomorphous Substitution of In3+ with Bi3+

Abstract Frustrated Lewis pairs (FLPs) created by sterically hindered Lewis acids and Lewis bases have shown their capacity for capturing and reacting with a variety of small molecules, including H 2 and CO 2 , and thereby creating a new strategy for CO 2 reduction. Here, the photocatalytic CO 2 reduction behavior of defect‐laden indium oxide (In 2 O 3− x (OH) y ) is greatly enhanced through isomorphous substitution of In 3+ with Bi 3+ , providing fundamental insights into the catalytically active surface FLPs (i.e., InOH···In) and the experimentally observed “volcano” relationship between the CO production rate and Bi 3+ substitution level. According to density functional theory calculations at the optimal Bi 3+ substitution level, the 6s 2 electron pair of Bi 3+ hybridizes with the oxygen in the neighboring InOH Lewis base site, leading to mildly increased Lewis basicity without influencing the Lewis acidity of the nearby In Lewis acid site. Meanwhile, Bi 3+ can act as an extra acid site, serving to maximize the heterolytic splitting of reactant H 2 , and results in a more hydridic hydride for more efficient CO 2 reduction. This study demonstrates that isomorphous substitution can effectively optimize the reactivity of surface catalytic active sites in addition to influencing optoelectronic properties, affording a better understanding of the photocatalytic CO 2 reduction mechanism.