Sustainable Synthesis And Characterization Of Nh2- Mil-53(Al)/Mil-100(Fe) Heterojunctions For Visible Light Driven Photocatalytic Degradation Of Rhodamine B Dye

Abstract

Water pollution caused by toxic dyes from the textile industry has become a major concern nowadays. Specifically, rhodamine B (RhB) dyes found in textile wastewater have harmful and toxic impacts on the surroundings and human health. To address these problems, photocatalytic wastewater treatment using metal-organic frameworks (MOFs) and MOF-on-MOF heterojunctions has emerged as a promising and dynamic research area. This is due to the unthinkable properties of MOFs. However, pristine MOFs often have low photocatalytic efficiency due to their wide band gaps and high electron-hole recombination rates, which limits their practical application. Coupling two different MOFs into MOF-on-MOF heterojunctions can help overcome these limitations. The heterojunction structure facilitates precise charge transfer interfaces, thereby increasing the photocatalytic activity of the MOFs. Additionally, the heterojunction can preserve the porous framework of the MOF materials, supporting both adsorption and photocatalytic behaviors. This study describes the sustainable synthesis of pristine MIL-100(Fe) and NH2-MIL-53(Al) MOFs, as well as the NH2-MIL-53(Al)/MIL-100(Fe) heterojunctions. Characterization techniques such as X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, Scanning electron microscopy (SEM), DRS-UV-vis spectroscopy (DRS-UV-vis) and so on were used to confirm the successful synthesis of the materials under environmentally friendly, energy-efficient, and economical (3E) conditions. The formation of the NH2-MIL-53(Al)/MIL-100(Fe) heterojunctions significantly enhanced the photo-responsive range and charge separation efficiency, leading to improved photocatalytic activity in the degradation of RhB dye. Under visible light irradiation, the NH2-MIL-53(Al)/MIL-100(Fe)-1wt% catalyst showed the highest performance, achieving 95.28% degradation efficiency within 140 minutes, outperforming the individual components. The active site trapping study revealed that superoxide radicals (•O2 - ) and holes (h+ ) play crucial roles in the photodegradation of RhB. Moreover, the selected photocatalyst revealed remarkable recyclability, retaining a high photocatalytic degradation efficency of 83.0% even after four cycles of activity.