Selective photocatalytic CO2 reduction in aerobic environment by microporous Pd-porphyrin-based polymers coated hollow TiO2

Direct photocatalytic CO₂ reduction from primary sources, such as flue gas and air, into fuels, is highly desired, but the thermodynamically favored O₂ reduction almost completely impedes this process. Herein, we report on the efficacy of a composite photocatalyst prepared by hyper-crosslinking porphyrin-based polymers on hollow TiO₂ surface and subsequent coordinating with Pd(II). Such composite exhibits high resistance against O₂ inhibition, leading to 12% conversion yield of CO₂ from air after 2-h UV-visible light irradiation. In contrast, the CO₂ reduction over Pd/TiO₂ without the polymer is severely inhibited by the presence of O₂ ( ≥ 0.2 %). This study presents a feasible strategy, building Pd(II) sites into CO₂-adsorptive polymers on hollow TiO₂ surface, for realizing CO₂ reduction with H₂O in an aerobic environment by the high CO₂/O₂ adsorption selectivity of polymers and efficient charge separation for CO₂ reduction and H₂O oxidation on Pd(II) sites and hollow TiO₂, respectively.