Enhanced Photocatalytic CO₂ Reduction to Methanol over Eco-Friendly CuCo-ZIF@g-C₃N₄ Synthesized from Recyclable Resources

The present work is focused on designing a sustainable catalyst for the photocatalytic conversion of CO₂ to methanol under visible light irradiation. Notably, most catalysts are made of costly, nonearth-abundant metal resources, which can partially hinder the large-scale implementation of CO₂ utilization efforts. Thus, a highly efficient CuCo-ZIF@g-C₃N₄ composite photocatalyst was prepared using copper sulfate (CuSO₄) and cobalt sulfate (CoSO₄) recovered from mining waste. Notably, the resulting composite offers enhanced photocatalytic activity relative to the individual CuCo-ZIF and graphitic carbon nitride (g-C₃N₄) building blocks during CO₂ assessed separately. Also, the catalyst's morphology, structure, and photoelectrochemical characteristics were accessed, and the photocatalytic mechanism and synergy between the composite components were systematically explored. The catalytic process was optimized via response surface methodology, dramatically improving the initial methanol yield from 1018.65 μmol/g_cat to an impressive 1876.8 μmol/g_cat with an apparent quantum yield of 0.139%. The results from this study provide insight into the application of sustainable resources for CO₂ photoreduction.