Robust Zinc Metal–Organic Framework-5 for Selective Landfill Methane Capture: Synthesis and Physicochemical Property Analysis ^†

Landfills are the third leading source of methane (CH₄) emissions. Engineering controls aim to capture methane and utilize it as an energy source using metal–organic framework systems during active periods or in abandoned landfills. Due to its exceptional physical features and tunable nature, adsorption on metal–organic frameworks (MOFs) presents itself as a potentially viable alternative for methane-selective separation/adsorption. As a result of some complex inherent features, it has proven challenging to comprehensively synthesize MOFs for methane capture and to evaluate their physicochemical properties using conventional techniques.

The aim of this study is to synthesize and optimize a zinc metal–organic framework (Zn-MOF-5) under various conditions of temperature, ranging from 85 °C to 90 °C, as well as a reaction time from 24 h to 48 h, and test its suitability for selectively capturing landfill methane through comprehensively exploring its physicochemical properties, including the functional groups, crystallinity and thermal stability using Fourier Transform Infrared (FTIR), X-ray Diffraction (XRD) and Thermogravimetric Analysis (TGA). The Zn-MOF-5 material revealed broad bands at 2980 and 2871 cm⁻¹, which are attributed to the C-H stretching vibrations of the methylene–alkane groups in the DEF molecule and the asymmetric stretching vibration of the C=O group linked to Zn at 1658 cm⁻¹. The XRD obtained broad peaks, which indicated an increasing regularity of the crystalline structure and better alignment layers with 0.92–1.04 cm³/g micropores, and the material was proven through TGA to be thermally stable up to a temperature of 500 °C.