Enhanced photocatalytic degradation of bisphenol A over N,S-doped carbon quantum dot-modified MIL-101(Fe) heterostructure composites under visible light irradiation by persulfate

A novel nitrogen- and sulfur-doped carbon quantum dot-modified MIL-101(Fe) (N,S:CQD/MIL-101(Fe)) heterojunction for visible light-induced activation of persulfate (PS) for bisphenol A (BPA) degradation was studied. The photocatalytic performance of BPA degradation was remarkably promoted by the composite material under the simultaneous action of PS and visible light irradiation. BPA photodegradation (100%) was achieved over 60 min with 0.4 g/L of the N,S:CQD/MIL-101(Fe) composite and 3 mM PS at natural pH. The degradation kinetics rate constants (k) approached 3.6 times higher than that of MIL-101(Fe). The enhanced performance in BPA degradation can be ascribed to the interfacial transference of photoinduced electrons from N,S:CQD to MIL-101 (Fe), leading to the valid separation of electron-hole pairs and greatly accelerating PS activation to generate highly reactive SO4 center dot- . Both holes (h+), sulfate radicals (SO4 center dot- ), superoxide radicals (center dot O2- ), and hydroxyl radicals (center dot OH) contributed to BPA degradation according to radical quenching experiments. N,S:CQD/MIL-101 (Fe) also exhibited great reusability and excellent catalytic performance after four consecutive cycles of use. This work provides valid organic contaminant degradation under the dual action of visible light and PS with a novel perspective on the fabrication of heterojunction photocatalysts ground on Fe-based MOFs.