Analytical evaluation of an Ag-MOF photocatalyst for efficient malachite green degradation in wastewater: kinetics, mechanism, and stability

Abstract

This work used a one-step solvothermal approach to construct a porous silver-based organic framework (Ag-MOF). The produced photocatalyst was thoroughly characterized using a variety of analytical methods, including FT-IR, UV-Vis, XRD, SEM, EDX, TEM, and BET analyses, to assess its surface morphology and crystal structure. According to DFT and UV-vis spectroscopic analyses, the bandgap energy of the Ag-MOF is around 2.9 eV. The influence of various experimental parameters such as the pH of the medium, dye concentration, amount of catalyst, and contact time for the degradation of the Malachite Green (MG) dye was examined. At optimum conditions (3 g L⁻¹ of catalyst, pH 8, and 100 mg L⁻¹ of the Malachite Green dye). The prepared Ag-MOF shows high photocatalytic activity of 97% at 90 min of reaction. Surface acidity investigations show that the total number of acid sites is 4.16 × 10²⁶ acid sites per g. The preservation of more than half of the photocatalytic activity, even after 6 cycles of degradation, shows the stability and reusability of the prepared MOF. Comprehensive tests, including PL, TOC analysis, leaching studies, and pollutant degradation, were carried out to confirm the photocatalytic performance, mechanism, stability, and safety of the catalyst. Scavenging studies concluded that the inclusion of an O₂˙⁻ scavenger significantly reduced the degradation efficiency to 31.12%. The study was extended to the use of the synthesized Ag-MOF for the synthesis of 7-hydroxy-4-methyl coumarin.