Synthesis of a UiO-66/g-C3N4 composite using terephthalic acid obtained from waste plastic for the photocatalytic degradation of the chemical warfare agent simulant, methyl paraoxon

In our study, Zr-based UiO-66 (Zr) was synthesized using terephthalic acid obtained from waste plastic. Thereafter, UiO-66/g-C3N4 composites were prepared by the solvothermal method, and their photocatalytic activity in the photodegradation of the chemical warfare agent simulant, dimethyl 4-nitrophenyl phosphate (DMNP), was evaluated. The as-synthesized UiO-66/g-C3N4 exhibited a high surface area (1440 m2 g−1) and a high capillary volume (1.49 cm3 g−1). The UiO-66/g-C3N4 samples absorbed a visible light band with bandgap energies of 2.13–2.88 eV. The as-synthesized UiO-66/g-C3N4 composites exhibited highly efficient degradation of DMNP with a short half-life (t1/2 of 2.17 min) at pH 7 under visible light irradiation. The trapping experiments confirmed that the h+ and ·O2− radicals played an important role in the photocatalytic degradation of DMNP. The UiO-66/g-C3N4 catalyst simultaneously performed two processes: the hydrolysis and photocatalytic oxidation of DMNP in water. During irradiation, a p–n heterojunction between UiO-66 and g-C3N4 restricted the recombination of photogenerated electrons and holes, resulting in the enhancement in the degradation rate of DMNP.