Enhanced Photocatalytic Performance of ZIF-67@ZIF-11 in Binary MOF Systems for Rapid Removal of Persistent Organic Pollutants

Abstract

Freshwater availability is a growing global concern as dye pollution is drastically lowering the quality of water on a massive scale. To reduce water pollution, photodegradation of persistent organic pollutants particularly dyes has recently become a practical option. Herein, ZIF-67, ZIF-11, and composite ZIF-67@ZIF-11 are synthesized via a solvothermal approach, and the materials were further investigated for photodegradation of MB dye solution. These hybrid materials were comprehensively characterized using SEM, EDS XDR, FTIR, and UV–visible spectroscopy. The band gap energy of ZIF-67, ZIF-11, and ZIF-11@ZIF-67 was determined via the UV–visible spectra and is estimated by the Tauc Plot method. Of the as-synthesized hybrid materials, optimized ZIF-67@ZIF-11 demonstrated excellent photodegradation of 95% of 10 ppm Methylene blue (MB) dye solution in the presence of solar light radiation within 50 min. This remarkable photocatalytic efficiency, capitalized by a two-fold hybrid material, may be related to the creation of defects and the ensuing enhanced spectral range of visible light radiation because of the smaller and pertinent band gap energy. According to the reusability experiment, ZIF-67@ZIF-11 has sustained 81% degradation efficiency even after five consecutive cycles. Furthermore, the trapping experiment demonstrated that the photodegradation of MB dye is mostly mediated by superoxide (O^.−₂) and hydroxyl (OH^.) radicals. Based on the results of the photodegradation of MB, ZIF-67@ZIF-11 may be a viable option for the elimination of dyes from wastewater.