Aerogel-stabilized ultrafine Cu2O with lattice strain for enhanced photocatalytic conversion of CO2 to methanol.

CO2 photoreduction represents a sustainable route for solar fuel production. For photocatalysts, particle size and lattice distortion are the two key factors affecting their activity. To obtain ultrafine Cu2O with lattice strain for converting CO2 to methanol, a novel three-dimensional monolithic aerogel photocatalyst was developed via coordination chemistry. The chitosan/citric acid aerogel provides a cross-linked network and abundant anchoring sites for uniform Cu2O nanoparticle dispersion. Coordinative interactions between Cu+ ions and surface carboxyl/amino groups enable precise confinement of Cu2O particle size within an extremely fine size range (5-30 nm). This dimension lies between twice the exciton Bohr radius (∼5 nm) and the carrier diffusion length (30-200 nm), facilitating the preservation of visible light response while suppressing electron-hole recombination. Moreover, interfacial interactions induce lattice distortions, generating an internal electric field that promotes charge separation. The synergism of quantum size and defects enables a methanol yield of 22,700.3 μmol g-1 h-1 with 100% selectivity, representing a 12.9-fold enhancement compared to powdered Cu2O, while demonstrating stable recyclability.