Hydrogen-Bond-Network Breakdown Boosts Selective CO₂ Photoreduction by Suppressing H₂ Evolution

Conventional strategies for highly efficient and selective CO2 photoreduction focus on the design of catalysts and cocatalysts. In this study, we discover that hydrogen bond network breakdown in reaction system can suppress H-2 evolution, thereby improving CO2 photoreduction performance. Photosensitive poly(ionic liquid)s are designed as photocatalysts owing to their strong hydrogen bonding with solvents. The hydrogen bond strength is tuned by solvent composition, thereby effectively regulating H-2 evolution (from 0 to 12.6 mmol g(-1) h(-1)). No H-2 is detected after hydrogen bond network breakdown with trichloromethane or tetrachloromethane as additives. CO production rate and selectivity increase to 35.4 mmol g(-1) h(-1) and 98.9 % with trichloromethane, compared with 0.6 mmol g(-1) h(-1) and 26.2 %, respectively, without trichloromethane. Raman spectroscopy and theoretical calculations confirm that trichloromethane broke the systemic hydrogen bond network and subsequently suppressed H-2 evolution. This hydrogen bond network breakdown strategy may be extended to other catalytic reactions involving H-2 evolution.