Synthesis of three-dimensional MgAl-LDO@ZnO and investigation of its synergistic adsorption-photocatalytic degradation mechanism

MgAl-LDH was widely recognized as an excellent support material for photocatalysts, yet its intrinsic hydrophilicity remains limited. In this study, the hydrophilicity of LDHs was effectively enhanced by transforming their two-dimensional plate-like structure into a three-dimensional flower-like morphology, which was subsequently pyrolyzed to obtain LDOs. ZnO microspheres were then deposited onto the LDOs through a low-co-solvent method, yielding a three-dimensional MgAl-LDO@ZnO composite catalyst with enhanced degradation activity. This composite provides a novel material option for adsorption-photocatalytic synergistic degradation of organic pollutants. This compositional combination not only enhanced hydrophilicity but also improved visible-light absorption and facilitates charge separation, thereby substantially enhancing catalytic performance compared to individual materials. Experimental results demonstrated that, compared to MgAl-LDH adsorption alone, the three-dimensional MgAl-LDO@ZnO exhibited approximately 2.5-fold improvement, achieving a degradation rate of 97.8% for basic fuchsin within 50 min, and retaining more than 90% adsorption-photocatalytic efficiency after five cycles. Infrared spectroscopy monitoring revealed intensified and broadened -OH stretching vibrations during degradation, while the characteristic peak of basic fuchsin disappeared, further confirming the degradation pathway. Active species trapping experiments identified ·OH and ·O 2 − as the dominant reactive species responsible for driving degradation. DFT calculations indicated that C1–9, N1, N2 and N3 serve as the primary active sites for radical attack. These findings confirmed the outstanding performance of MgAl-LDO@ZnO, demonstrated its practical applicability, and provided a promising strategy for constructing highly efficient and stable adsorption-photocatalytic degradation systems.