Frustrated Lewis Pairs on In(OH)3–x Facilitate Photocatalytic CO2 Reduction

Photocatalysis is promising for the reduction of CO2 into fuels and chemicals under mild conditions but is still a challenge due to the inert nature of CO2. Herein, a ZnIn2S4/In(OH)3–x (ZIOS) heterojunction was developed for visible-light-driven CO2 reduction, where ZnIn2S4 (ZIS) harvests the light and In(OH)3–x with frustrated Lewis pairs (FLPs) activates the CO2. The hydroxyl-deficient vacancies (OHVs) of In(OH)3–x act as a Lewis acid, and the adjacent hydroxyl groups serve as a Lewis base to form FLPs. The ZIOS composites are fabricated via partial sulfurization of Zn–In–O oxide, constructing a type II heterojunction that facilitates the photogenerated electron transfer from ZnIn2S4 to reduce FLP-activated CO2 on In(OH)3–x. The as-prepared ZIOS composites exhibit a CO formation rate of 1945.5 μmol·g–1·h–1, which is about 2.76-fold higher than that over ZnIn2S4, and suppress hydrogen evolution with the CO/H2 ratio increasing from 0.436 for ZnIn2S4 to 1.6 for ZIOS. This work provides insight into the design of efficient CO2 reduction photocatalysts.