Selective glyphosate degradation via oxygen activation using Fe-N-C: Critical role of size exclusion

Selective elimination of glyphosate (PMG) from complex water matrices remains a significant challenge. Metal-nitrogen-carbon (M-N-C) materials derived from metal-organic frameworks (MOFs) offer a promising platform due to their tunable porosity and abundant active sites. In this study, three Fe-N-C-x (x = 5, 10, 20) catalysts with varying pore sizes (2-4 nm) and no surface-active sites were synthesized for PMG degradation under interference with contaminants of different sizes. The results showed Fe-N-C-5 exhibited superior catalytic and anti-interference performance for PMG degradation compared to Fe-N-C-10 and Fe-N-C-20. This was attributed to the greater accessibility of smaller-sized PMG (molecular size 0.9 nm) to the internal active sites through the pore channels, while larger-sized pollutants were effectively excluded. Zeta potential measurements and in situ ATR-FTIR spectroscopy revealed that the entrance of PMG was driven by both electrostatic interaction and coordination bonding between phosphate and Fe in Fe-N-C-5. Quenching experiments combined with electron spin resonance (ESR) analysis confirmed that singlet oxygen (¹O₂) was the primary reactive oxygen species responsible for PMG degradation in the Fe-N-C-5/O₂(Vis) system. This study highlights the robust anti-interference capability of Fe-N-C-5 and provides new insights into its potential applications in advanced water treatment technologies.