In situ thermal solvent-free synthesis of doped ZIF-8 as a highly efficient visible-light-driven photocatalyst†

Abstract

Developing an economical and effective catalyst to remove organic pollutants from wastewater remains a significant challenge to maintaining a healthy, green environment. The metal–organic frameworks (MOFs) have drawn considerable attention to renewable energy and environmental remediation due to their porous crystalline structure. In this context, we develop a straightforward, environmentally friendly, solvent-free, in situ thermal (IST) method to synthesize doped zeolitic imidazole frameworks (ZIF-8). The solvent-free IST technique surpasses the traditional synthesis procedures in efficiency due to a single-step and solvent-free process with a short processing time and a low precursor ratio. Notably, doped ZIF-8 photocatalysts against concentrated methylene blue (MB) and rhodamine B (RhB) degradation exhibit superior photocatalytic performance under visible light exposure. An in-depth study of the effect of dye concentration and pH on doped ZIF-8 is also performed. The kinetic study via photocatalytic isotherms confirms that the photodegradation mechanism follows the pseudo-first-order kinetic model. Following active species trapping experiments, we confirm that the hydroxyl radicals play a substantial role in MB degradation with optimized Fe@ZIF-8. Moreover, the Fe@ZIF-8 does not significantly lose its photocatalytic activity for degrading MB after three cycles, indicating its enduring reusability and stability. Thus, this study provides a novel approach to developing the doped MOF as a photocatalyst with enhanced photocatalytic activity for wastewater treatment.