Nanoconfined CsPbBr3 in Boron-Doped Mesoporous TiO2 Enables Built-In Electric Field Modulation for fully Selective CO2-to-CO Photoconversion

Achieving single-product selectivity in photocatalytic CO₂ reduction remains an enormous challenge. Although modulating a catalyst’s nanoconfined environment can mitigate the co-production of CO and CH4 in CO2 reduction, the contribution of nanoconfined architecture to interfacial built-in electric field (BIEF) regulation for solid-gas CO2 conversion has received limited attention. Herein, CsPbBr3 quantum dots (QDs) are grown in situ within the ordered porosity of boron-doped mesoporous TiO2 (BMT) for CO2 photoreduction under simulated solar irradiation. The composite CsPbBr3@BMT delivers a CO production rate of 226 μmol·g-1·h-1 with essentially 100% (99.9%) selectivity in a solid-gas system, outperforming state-of-the-art CsPbBr3-based photocatalysts under comparable conditions. The new CsPbBr3@BMT architecture integrates pore-level stabilization of QDs, with the nanocage framework isolating and stabilizing the QDs, as evidenced by in situ XPS and TEM. The combination of boron doping and nanoconfinement is shown by theoretical calculations to enhance the BIEF between the QDs and BMT, leading to improved charge separation and suppressed hydrogen evolution. In addition, calculations reveal that nanoconfinement stabilizes the COOH intermediate in CO2 photoreduction while weakening CO adsorption, directing the system towards CO formation and release. These results highlight nanoconfinement as an effective strategy for selective, efficient solar-driven CO2-to-CO conversion.