Waste-derived hollow MnFeOx@SiO2 tubes enable triple synergy: Silanol-buffered microenvironments, D-band modulated, and photon trapping for ultrafast alkaline complex wastewater purification

Green iron-based materials suffer from severe alkaline deactivation and limited photoactivity, restricting synergistic pollutant remediation. Herein, a bioinspired microenvironment engineering strategy to convert copper slag into amorphous SiO 2 -stabilized Mn-doped ferrous oxalate hollow tubus (MnFeOx@SiO 2 ). In the complex, amorphous SiO 2 neutralizes external alkalinity, while Si−OH dissociation maintains an weak-acidic microenvironment, preventing hydrolysis deactivation and ensuring robust photo-Fenton cycles. Experimental and DFT studies reveal that silicate-derived silica gel synergizes with glycerol to direct MnFeOx axial growth, forming channeled hollow tubes that enhance light harvesting and mass transfer. Concurrently, Mn doping builds Fe−O−Mn interfaces optimizing Fe d -band centers via d-d hybridization, accelerating charge separation. The catalyst showed exceptional performance under wide pH range (pH 2 −9), achieving 96.4 % methyl orange degradation and 98.2 % Cr(VI) reduction within 5 min. It exhibits 22.1/10.0-fold activity enhancement over FeC 2 O 4 under alkaline conditions and > 85.1 %/85.4 % stability after ten cycles. This work pioneers waste-derived catalysts for pH-universal water purification.