Coal-based carbon quantum dots modified Ag3PO4/Ni-MOF composites enhanced visible light photocatalytic degradation of phenol

Coal tar pitch-based carbon quantum dots (CQDs) were meticulously prepared via ball milling. Ag3PO4/Ni-MOF/CQDs composites were synthesized through an in-situ precipitation method, and their performance as composite catalysts for the photocatalytic degradation of phenol was thoroughly investigated. Among these composites, Ag-Ni-70/CQDs-0.45 emerged as the most effective catalyst, achieving a remarkable degradation rate of 98% for 10 mg/L phenol within just 30 min, with a corresponding rate constant of 0.0620 min−1. Notably, the photocatalytic degradation of phenol exhibited robust activity across a spectrum of pH levels, different water matrices, and varying concentrations of anions (SO42−, Cl−, CO32−, HPO42− and HCO3−). Furthermore, after undergoing 4 cycles of reaction, the catalyst demonstrated commendable stability. The outcomes of free radical capture experiments revealed that the primary active species involved in the degradation process were ·OH and h+. The electron transport pathways were analyzed based on the band gap structure of the catalyst, and a possible degradation mechanism was proposed. Upon the combination of Ni-MOF and Ag3PO4, the alteration of metal-O bonds facilitated the formation of a tightly bonded interface, thereby establishing a Z-scheme heterojunction. The introduction of CQDs as an electron transport medium accelerated electron transfer, mitigated the recombination of photogenerated charges, and thereby enhanced the photocatalytic performance of the heterostructure.