Hafnium melamine-based metal-organic frameworks for efficient hydrogen release from sodium borohydride in methanol

A novel hafnium-melamine metal-organic framework (Hf-MEL MOF) was successfully synthesized via a solvothermal approach, utilizing melamine and hafnium (IV) chloride (HfCl4) in ethanol at 78 °C. Comprehensive characterization techniques, including Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Raman spectroscopy, and scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM-EDX), were employed to elucidate its structural, molecular, and morphological properties. Hydrogen production through the methanolysis of sodium borohydride (NaBH4) was systematically evaluated, highlighting the exceptional performance of the Hf-MEL MOF catalyst. Under the optimal reaction conditions, 5 mg of catalyst, 150 mg of NaBH4, and 2 mL of methanol at a temperature of 30 °C, the material reached a high hydrogen generation rate (HGR) of 78.75 L/min.gcatalyst. The kinetic studies through the Arrhenius equation gave an activation energy (Ea) of 10.7 kJ/mol. Density functional theory calculations (DFT) confirmed the excellent catalytic performance of the catalyst with an energy gap (ΔEgap) of 2.122 eV. Furthermore, the catalyst showed a notable stability, with activity maintained for five consecutive cycles with no apparent loss in performance. The results hence place Hf-MEL MOF as a highly efficient and robust catalyst toward hydrogen production, with its applicability in practice for sustainable and portable hydrogen-based energy systems.