Synergistic photocatalysis of bimetal mixed ZIFs in enhancing degradation of organic pollutants: Experimental and computational studies

The present work is aimed at studying the synergistic catalysis of the bimetal ZIFs containing Co and Zn metal ions prepared by solvothermal method in the degradation of organic pollutants under ambient conditions. The bimetal mixed ZIFs were further characterized by some techniques such as XRD, SEM, TG-DTG, XPS, UV–vis, ESR, and N2-adsorption. Interestingly, the sample prepared with equal metal ions (1Zn:1Co) showed the highest catalytic performance for methylene blue (MB) degradation (94.10 %). This may be associated with the interaction between cobalt and zinc within the adjacent lattice, which make the MB molecule to be easily adsorbed and degraded on empty electron orbit. Furthermore, the highest degradation of MB was achieved with 98.83 % under the optimized conditions (catalyst weight of 50 mg, pH of 5, 3 h, 30 °C). Besides, the various substrates such as methyl orange, indole, rofloxacin, methyl blue, and tetracycline were also investigated under the same conditions. Additionally, the DFT calculation results suggested the more orbital distribution (LUMO, HOMO) of ZIF(1Zn:1Co) can result to more electrons being easily captured, and generate more radicals via electron transfer. Finally, the photocatalytic degradation of MB is consistent with the first law of kinetics, and the activation energy is 26.797 KJ/mol in the presence of ZIF(1Zn:1Co).