Near-infrared-active Nd-BiO_2-x/MIL-101(Fe) with vacancy-induced interfaces for solar water purification

Engineering vacancy interfaces in semiconductor-metal-organic framework heterostructures provides a promising route to regulate interfacial charge transfer under solar irradiation. Here, we construct a near-infrared-active Nd-BiO_2-x/MIL-101(Fe) heterostructure, where ultrathin oxygen-vacancy-rich Nd-doped BiO_2-x nanosheets (2-5 nm) are anchored onto porous MIL-101(Fe) through Bi-O = C bonds. The vacancy-induced interface establishes an intrinsic built-in electric field and stabilizes a direct Z-scheme charge-transfer pathway. Nd doping generates asymmetric oxygen vacancies that narrow the bandgap, enhance near-infrared absorption, and strengthen O₂ imprint adsorption. The catalyst exhibits a 1.9-fold increase in bisphenol AF degradation under full-spectrum irradiation compared with near-infrared-filtered light, with singlet oxygen and photogenerated holes acting synergistically. In a flat-plate continuous-flow reactor under natural sunlight, the system achieves stable removal of eleven emerging contaminants with negligible Bi³⁺ leaching. This work presents a vacancy-interface strategy for built-in electric field-driven solar micropollutant removal.