Synthesis and Characterization of Ag@M-BTC (M = Zn & Cd) Nanocomposites for Efficient Removal of Methylene Blue and Indigo Carmine

Two MOF based composite materials decorated with Ag NPs viz. Ag@M-BTC (BTC= 1,3,5-benzenetricarboxylate; M=Zn & Cd) were synthesised and characterized using various physicochemical techniques, including FT-IR, PXRD, FE-SEM, EDX, HR-TEM, BET and XPS. The FT-IR spectra of the nanocomposites (NCs) and the pristine MOFs suggest retention of the MOF structure in the resulting composite materials and the PXRD patterns confirm the presence of metallic Ag within the crystalline phase of the MOFs. The observed rough surfaces on the NCs as evidenced from FE-SEM micrographs, indicates the deposition of Ag NPs on the surface of the MOFs. Furthermore, HR-TEM images reveal the presence of nanosized Ag aggregates of spherical shape inside the MOF matrix as well as on the surface. The adsorption activity of the synthesised NCs have been assessed for Methylene Blue (MB) and Indigo Carmine (IC). It is observed that the NCs, Ag@Zn-BTC (1a) and Ag@Cd-BTC (2a) performs better degradation as compared to that of pristine MOFs. These NCs can degrade MB completely (100%) after 50 min treatment time, while maximum 91% degradation was recorded for the IC dye. Here, the degradation process can be thought of as operating via chemisorption phenomena, supported by theoretical calculations. Additionally, these NCs can be reused up-to three times for the effective degradation of dyes.