Effect of solvent selection on Zn-MOFs synthesized for hydrogen storage applications
Mohammed S. Alnafisah, Khalid N. Alharbi, Naif S. Almuqati, Khawla M. Almalahi, Mohammed H. Almusawa, Dakelallah D. Almotairy, Ghaida Alotaibi, Abdulaziz I. Alromaeh
Abstract
Metal–organic frameworks (MOFs) have emerged as promising candidates for hydrogen storage due to their high surface area and tunable porosity. However, most MOFs require high pressures to achieve significant hydrogen uptake, limiting their practical applications. This study explores the impact of solvent selection on the synthesis and hydrogen storage performance of Zn-based MOFs, specifically ZIF-8, using solvothermal and hydrothermal techniques. ZIF-8 was synthesized in water, methanol (MeOH), and N,N-dimethylformamide (DMF), and its structural properties were characterized using Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and Brunauer-Emmett-Teller (BET). The hydrogen adsorption capacity was evaluated at 1 and 10 bar under 77 K and 298 K conditions. The results indicate that hydrogen uptake improves with increasing pressure, with ZIF-8 achieving a maximum uptake of 21.12 % at 77 K and 10 bar, while retaining a substantial capacity of 20.35 % at 298 K and 10 bar. At lower pressures (1 bar), ZIF-8 exhibited an uptake of 18.77 % at 77 K and 18.26 % at 298 K, confirming its efficiency in hydrogen storage at relatively mild conditions. Additionally, the solvent used during synthesis significantly influenced the adsorption properties, with ZIF-8 synthesized in water demonstrating superior uptake, particularly at 10 bar (20.35) compared to methanol (19.48) and DMF (18.26). These findings highlight the crucial role of solvent selection in tailoring MOF performance and position ZIF-8 as a potential candidate for efficient hydrogen storage at moderate pressures. The study underscores the feasibility of ZIF-8 for scalable and energy-efficient hydrogen storage applications, reducing dependence on high-pressure storage systems. • ZIF-8 was synthesized using different solvents via solvothermal and hydrothermal methods. • PXRD and SEM confirmed the influence of solvent selection on ZIF-8 crystallinity and morphology. • ZIF-8 synthesized in water showed the highest hydrogen uptake of 18.26 and 20.35 at 1 and 10 bar. • Hydrogen storage performance was evaluated at different pressures and compared with literature. • ZIF-8 demonstrated superior hydrogen uptake at 1 bar compared to reported MOFs.