Boosting Photocatalytic CO₂ Reduction with H₂O by Oxygen Vacancy- and Hydroxyl-Tailored SrBi₂Ta₂O₉ Surface-Frustrated Lewis Pairs

The photocatalytic reduction of CO₂ into high-value-added fuels is an extremely desirable process, but its practical application is limited by the weak adsorption and activation of inert CO₂ molecules. Herein, oxygen vacancies (V_Os) are formed on SrBi₂Ta₂O₉ (SBT) by annealing in Ar gas at 400 °C and can spontaneously react with adsorbed H₂O to form surface hydroxyls. Therefore, frustrated Lewis pairs (FLPs) are fabricated on SBT, where the surface V_O and proximal surface hydroxyl serve as the Lewis acid and base, respectively. Experimental results indicate that the obtained FLPs can act as catalytic sites to adsorb, activate, and convert CO₂ under low-intensity LED light irradiation (420 nm). Consequently, a CO₂-to-CO conversion rate of 9.9 μmol g^-1 h^-1 is achieved in pure water on V_O-SBT-OH without any sacrificial agents or cocatalysts, which is ∼4× higher than that of pristine SBT. Moreover, the surface hydroxyl can self-replenish by dissociating H₂O during the reaction, thereby achieving a long-term CO₂ conversion for 60 h. Our study demonstrates the potential of FLPs as a platform to decrease barriers to reducing CO₂ and provides valuable insights into the underlying photocatalytic mechanism.