Kaolin-based metal-organic frameworks for sustainable natural gas storage

Abstract

Natural gas (NG) is increasingly regarded as one of the most environmentally friendly forms of energy. However, low volumetric density, high leakage rate and explosion during transportation and storage limit the accessibility and consumption of NG. To bridge the gap, this work reports on the formulation of metal-organic frameworks (MOFs) for onboard storage of natural gas using kaolin clay, chitosan, dimethyl sulfoxide, potassium acetate and (3-mercaptopropyl) trimethoxysilane. Results of formulated MOFs (CKO, PKT, DKT, DKO, and PKO) from the thermogravimetric analysis showed that the thermal stability ranged from 226 to 550 °C implying that the MOFs at this temperature range can maintain their structural integrity and resist decomposition throughout the adsorption process. The results of Porosimetry indicated that the synthesized MOFs exhibit a surface area within the range of 195.239–611.802 cm2/g and a pore volume ranging from 0.412 to 0.967 cm3/g. These findings suggest that the prepared MOFs possess a practical adsorption capacity for natural gas. Adsorption tests demonstrated that CKO and PKT MOFs exhibited higher natural gas (NG) adsorption capacities (0.028 and 0.017 g/g) over DKT, DKO, and PKO (0.014 g/g, 0.0095 g/g, and 0.0083 g/g) at 5 bar. These results underscore the increased capacity of MOFs to store significant quantities of natural gas under low-pressure conditions compared to previous literature. Conversely, the strong correlation coefficients (R > 0.95) observed in the adsorption isotherms of the developed MOFs provide confirmation that natural gas adsorption took place on uniform adsorption sites, aligning with the Langmuir adsorption isotherm. Overall, the findings of this study demonstrated the potential of kaolin-based metal-organic frameworks for use in the energy sector and expanded the search for sustainable onboard natural gas storage solutions.