Solar‐Driven CO ₂ and H ₂ O Conversion Over a High‐Density Nickel Single‐Site Catalyst With Unprecedented CO Evolution Rate

Achieving carbon dioxide (CO₂) reduction with water (H₂O) on photothermal catalysts remains a major challenge. Here, we report a high-density Ni single-site catalyst based on a porous aromatic framework (PAF), which enables efficient CO₂ reduction in pure H₂O under full-spectrum illumination without the need for additives. Ni-PAF achieves CO production rates of 25.64 mmol·g^-1·h^-1 under Xe light and 229.04 mmol·g^-1·h^-1 under concentrated sunlight, exceeding all reported results. Nitrogen-rich groups anchor Ni single sites uniformly, serving as the active centers for the activation of CO₂ and H₂O. Calculations and experiments show that UV-Vis light drives charge transfer, while IR absorption induces a localized temperature rise. Besides, the low thermal conductivity of PAF confines this heat, creating a thermal microenvironment that enhances charge migration and proton transfer, thereby accelerating CO₂ conversion. These synergistic effects make Ni-PAF a highly promising catalyst for solar-driven CO₂ reduction in H₂O and offer new opportunities for designing efficient photothermal catalysts toward solar fuel production.