Ultra-uniform MIL-88B(Fe)/Fe3S4 hybrids engineered by partial sulfidation to boost catalysis in electro-Fenton treatment of micropollutants: Experimental and mechanistic insights

[Display omitted] •MIL-88B(Fe)/Fe3S4 hybrids for effective water treatment by heterogeneous electro-Fenton.•Hybrid catalyst: highly uniform composition due to excellent distribution of small Fe3S4.•Sulfidation allows breaking the activity-stability trade-off for high performance HEF.•Good recyclability of hybrids and fast trimethoprim removal even in urban wastewater.•Great catalytic activity and degradation mechanism confirmed by DFT calculations. Fe-based metal–organic frameworks are promising catalysts for water treatment, although their viability is hampered by the slow regeneration of active Fe(II) sites. A facile sulfidation strategy is proposed to boost the catalytic activity of MIL-88B(Fe) in heterogeneous electro-Fenton (HEF) treatment of organic micropollutants at mild pH. The synthesized MIL-88B(Fe)/Fe3S4 hybrids possessed numerous and durable unsaturated iron sites, acting the S2− atoms as electron donors that enhanced the Fe(II) recycling. The sulfidated catalyst outperformed the MIL-88B(Fe), as evidenced by the 7-fold faster degradation of antibiotic trimethoprim by HEF and the fast destruction of micropollutants in urban wastewater. The hybrid catalyst was reused, obtaining >90% drug removal after four runs and, additionally, its inherent magnetism facilitated the post-treatment recovery. Electrochemical tests and DFT calculations provided mechanistic insights to explain the enhanced catalysis, suggesting that the accelerated Fe(III)/Fe(II) cycling and the enhanced mass transport and electron transfer accounted for the efficient trimethoprim degradation.