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

•Facet effect of MOFs on photocatalytic PMS activation is unveiled.•{111} facets of MIL-125-NH2 promotes the exposure of active sites.•The adsorption of PMS on {111} facets of MIL-125-NH2 is enhanced.•{111} dominated MIL-125-NH2 exhibits improved TC removal efficiency. 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 {001} dominated NM-1, {001} and {111} co-exposed NM-2 and {111} 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 {111} 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.