Electrostatic Attraction-Driven Assembly of a Metal–Organic Framework with a Photosensitizer Boosts Photocatalytic CO2 Reduction to CO

Reducing CO₂ into fuels via photochemical reactions relies on highly efficient photocatalytic systems. Herein, we report a new and efficient photocatalytic system for CO₂ reduction. Driven by electrostatic attraction, an anionic metal-organic framework Cu-HHTP (HHTP = 2,3,6,7,10,11-hexahydroxytriphenylene) as host and a cationic photosensitizer [Ru(phen)₃]²⁺ (phen = 1,10-phenanthroline) as guest were self-assembled into a photocatalytic system Ru@Cu-HHTP, which showed high activity for photocatalytic CO₂ reduction under laboratory light source (CO production rate of 130(5) mmol g^-1 h^-1, selectivity of 92.9%) or natural sunlight (CO production rate of 69.5 mmol g^-1 h^-1, selectivity of 91.3%), representing the remarkable photocatalytic CO₂ reduction performance. More importantly, the photosensitizer [Ru(phen)₃]²⁺ in Ru@Cu-HHTP is only about 1/500 in quantity reported in the literature. Theoretical calculations and control experiments suggested that the assembly of the catalysts and photosensitizers via electrostatic attraction interactions can provide a better charge transfer efficiency, resulting in high performance for photocatalytic CO₂ reduction.