Facet engineering of metal-organic frameworks for efficient tetracycline degradation by photocatalytic activation of peroxymonosulfate

Metal-organic frameworks (MOFs) represents a promising catalyst for photocatalytic peroxymonosulfate (PMS) activation, however their crystal facet effect is rarely explored. Herein, the impact of facet exposure of NH₂-MIL-125 on the photocatalytic activation of PMS toward tetracycline (TC) degradation is investigated. NH₂-MIL-125 crystals with controlled facets including {0 0 1} dominated NM-1, {0 0 1} and {1 1 1} co-exposed NM-2 and {1 1 1} dominated NM-3 are synthesized. Under optimized reaction condition, NM-3 exhibits the highest activity with higher TC removal efficiency, faster TC degradation kinetics and higher total carbon removal efficiency than NM-1 and NM-2. Experimental and theoretical results reveal that the {1 1 1} facet of NH₂-MIL-125 promotes the photocatalytic PMS activation by (1) exposing more active sites for PMS activation, (2) modulating the electronic structure with more positive d band center toward reinforced PMS adsorption and PMS decomposition into highly oxidative species. Our work unveils the crucial role of facet engineering of MOFs for photocatalytic PMS activation.