Multilayer Zn/Cu Oxides Derived from Zn/Cu-BDC Solvent-Exchanged by Alcohols with Different Molecular Sizes: Characterization and Photocatalytic Performance

Multilayer oxide catalysts can be obtained from pyrolyzing pillared layered metal-organic frameworks (MOFs). However, the effects of the filling solvent in the cavities of MOFs on the resulting catalyst are ignored. Herein, five alcohols were used to exchange the original solvent of the Zn/Cu-BDC MOF, subsequently deriving five corresponding catalysts. The photocatalytic degradation of 4-nitrophenol (4-NP) under UV-light irradiation was employed to verify the catalytic performance. Structural analysis revealed that the p-n junctions with amorphous hetero interfaces were formed in the catalysts, which collectively enhanced both light absorption characteristics and charge separation efficiency, leading to significantly improved catalytic activity. ZnO/CuO-BDC-Bu (prepared via <i>n</i>-butanol solvent exchange with a heating rate of 5 °C min^-1) exhibited superior photocatalytic activity, achieving 96.5% 4-NP degradation within 25 min. The <i>n</i>-butanol solvent molecules functioned as effective molecular spacers to expand the interlayer distance. The introduction of CuO modified the electronic structure of the composite, as evidenced by bandgap modulation and suppressed charge recombination. Radical trapping experiments identified hydroxyl radicals (•OH) and holes (h⁺) as the primary active species. This study provided a novel approach for increasing the interlayer spacing of the multilayer catalysts to improve the contact probability between reactants and catalyst active sites.