Preparation of Rare-Earth-Based Metal–Organic Frameworks and Their PMS Photocatalytic Activation for Rhodamine B Degradation

Organic dyes are commonly used in the textile and leather industries and are frequently detected in natural water bodies, posing potential hazards to the ecological environment and human health. Sulfate-radical-based advanced oxidation processes (SR-AOPs) possess strong oxidation capabilities and wide pH applicability and are widely used to treat organic dyes in wastewater. Designing a green, safe, and stable photocatalytic composite SR-AOP system remains a challenge. In this study, two new rare earth (RE)-based metal-organic framework (RE-MOF) photocatalysts (M-MOFs, where M = Ho, La) were synthesized via a coordination regulation strategy with RE ions. The results showed that La-MOF exhibited stronger light absorption and higher efficiency of photogenerated carrier separation than Ho-MOF. After 100 min of visible light irradiation, the rhodamine B (RhB) degradation efficiency of the La-MOF/PMS system reached 91.3%, with an apparent first-order rate constant of 0.025 min^-1, which was considerably superior to that of the Ho-MOF/PMS system. The feasible pathways for RhB degradation in wastewater and the toxicity of intermediate products were analyzed in detail. Overall, the synthesized RE-MOFs are effective for the removal of dyes from wastewater.