A Calcium Metal-Organic Gel as a Dual-Functional Material for Iodine Adsorption and a Catalyst for the Knoevenagel Condensation Reaction

Abstract A calcium metal-organic hydrogel (Ca-MOG) was synthesized using the glycine-derived gelator {(3,5-di-tert-butyl-2-hydroxybenzyl)amino} acetic acid (H3L). The metallogel was characterized using rheology, matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry, FTIR, field-emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), powder X-ray diffraction (PXRD), and thermogravimetric analysis (TGA). The adsorption of iodine by Ca-MOG (xerogel) was investigated. The xerogel exhibited iodine adsorption capacities of 1550 mg/g, 971.8 mg/g, and 371.1 mg/g in the vapor, organic, and aqueous phases, respectively. Kinetic and isotherm studies of adsorption in the organic and aqueous phases were conducted at pH 7 and room temperature. Adsorption isotherm and kinetic studies indicated that the adsorption process followed the Langmuir adsorption model and pseudo-second-order kinetics in both the organic and aqueous phases. Desorption and recyclability tests were also performed, suggesting the stability and reusability of the Ca xerogel. The xerogel was also used as an efficient heterogeneous catalyst in the Knoevenagel condensation reaction.