Photocatalytic reduction of CO ₂ with water to methanol over ZnO-TiO ₂ /FeMIL-88B composite

This study explores the synergistic effects among ZnO, TiO2, and FeMIL-88B in promoting the photocatalytic reduction of CO2 to methanol, with water serving as a reducing agent. A ZnO-TiO2 nanocomposite with a molar ratio of 1:5 was synthesized via a precipitation approach and subsequently anchored onto the FeMIL-88B framework. The physicochemical properties of the resulting materials were examined using SEM-EDS, XRD, BET, TGA, UV-vis DRS, and PL analyses. Photocatalytic experiments were conducted in the liquid phase under ambient conditions (25 °C, 1 atm). Throughout the reaction, no gaseous products were detected, while methanol was identified as the dominant liquid-phase product. The methanol production activity followed the order: TiO2 < ZnO-TiO2 (1:5) < FeMIL-88B < ZnO-TiO2(1:5)/FeMIL-88B. Notably, the ZnO-TiO2(1:5)/FeMIL-88B composite exhibited the highest performance, delivering a methanol yield of 126.8 μmol g−1cat after 4 h of irradiation. The obtained results suggest that photocatalytic efficiency is influenced by multiple interdependent factors, among which surface morphology and specific surface area play decisive roles. Furthermore, the integration of metal oxide semiconductors with MOF architecture effectively enhances interfacial charge transport and CO2 adsorption capability. Based on DRS, PL, BET, SEM, and photocatalytic results, a plausible heterojunction-assisted mechanism is proposed. Overall, the ZnO-TiO2(1:5)/FeMIL-88B composite demonstrates considerable potential as a robust and efficient photocatalyst for CO2 reduction in aqueous systems, benefiting from improved charge separation, structural integrity, and catalytic activity.