Synergistic and efficient photocatalytic CO₂ reduction over TiO2/UiO-66/Cu composites

Photocatalytic CO₂ reduction is a promising route for valorizing carbon resources. In liquid-phase systems, TiO 2 suffers from limited CO₂ adsorption, high interfacial charge-transfer resistance, and rapid carrier recombination. These drawbacks hinder simultaneous improvements in efficiency and selectivity. We fabricated a TiO 2 /UiO-66/Cu ternary photocatalyst using a modified-then-loaded strategy. Amino-functionalized TiO 2 was chemically anchored to UiO-66 via N–Zr coordination, forming a robust, low-resistance TiO 2 /MOF interface while preserving the CO₂-enrichment pores of UiO-66. Cu nanoparticles were then introduced as electron traps and catalytic sites to extract photogenerated electrons from the recombination-prone Type-I heterojunction, enabling directional electron utilization. In a solid–liquid system using water as the proton source, the optimal TiO 2 /UiO-66/Cu produced 86.76 μmol·g⁻¹ CO and 9.08 μmol·g⁻¹ CH 4 after 4 h of UV–visible irradiation. The CO production rate was 7.4- and 3.8-fold higher than that of pristine TiO 2 and UiO-66, respectively. Characterization shows that N–Zr coordination reduces charge-transfer resistance, UiO-66 enriches CO₂, and Cu promotes electron capture. Together, these effects mitigate the intrinsically poor charge separation of Type-I heterojunctions and enable efficient CO 2 photoreduction. The results provide design and mechanistic insights for MOF-enabled TiO 2 composite photocatalysts.