Rational Design of Zeolitic Imidazolate Framework-Metal Oxide Hybrids toward Green and Sustainable Photocatalysis

Innovative approaches are crucial for renewable growth in the face of growing environmental issues, including water pollution and dependence on fossil fuels. Zeolitic imidazolate frameworks, particularly ZIF-8, have emerged as potential photocatalysts for applications in renewable energy and environmental remediation. ZIF-8, a subset of MOFs, is notable for its high porosity, extensive surface area, rapid electron transfer, multiple functional capabilities, tunable properties, design flexibility, and remarkable thermal and chemical stability. However, factors such as particle agglomeration, limited water stability, and inadequate visible-light absorption restrict its standalone photocatalytic performance. To enhance the pristine ZIF-8 functionality, numerous researchers have developed composites with metal oxides (ZnO, TiO₂, Fe₂O₃, WO₃, SnO₂, CuO, etc.), demonstrating their efficiency in diverse photocatalytic applications. Metal oxides are excellent partners for ZIF-8, as they narrow the band gap, increase active sites, and boost photocatalytic efficiency. The strong interfacial interaction between ZIF-8 and metal oxides promotes charge transfer and efficient separation of photoinduced electron-hole pairs, reducing recombination losses. This review highlights ZIF-8 synthesis, fabrication of MO@ZIF-8 composites, characterization, and photocatalytic applications in H₂ generation, H₂O₂ evolution, Cr-(VI) reduction, and dye and drug degradation along with a mechanistic perspective. MO@ZIF-8 composites hold significant promise for sustainable energy and environmental solutions.