Non-surfactant template synthesis of highly porous Zn4O(BDC)3 and Cu3(BTC)2 metal–organic frameworks for efficient hydrogen storage: experimental insights and modeling analysis

This investigation successfully prepared two unique MOFs (Metal-Organic Frameworks), Zn 4 O(BDC) 3 and Cu 3 (BTC) 2 , utilizing Zn (II) and Cu (II) as central metal ions. An eco-friendly sol-gel technique was employed with water, ethanol, and sustainable 1-Decanol as a non-surfactant template. The synthesized adsorbents were characterized for pore textural properties (using nitrogen adsorption), crystal structure (using scanning electron microscopy), and phase structure analysis (using XRD). Additionally, DFT-D3 FT-IR was used to compare experimental vibrational spectra. The hydrogen storage mechanism into both Metal-Organic Frameworks (MOFs) is purely physical sorption, with a sorption enthalpy of −4.3 kJ/mol. Zn 4 O(BDC) 3 shows a maximum storage capacity of 5.38 % at high pressures and 77 K, the highest reported for crystalline microporous materials. Cu 3 (BTC) 2 demonstrates superior hydrogen uptake at low pressures, indicating its potential as a more promising candidate for hydrogen storage. Furthermore, the hydrogen correlates with the specific surface area for both MOFs and zeolites. QTAIM analysis reveals the adsorption mechanism and identifies the groups responsible for hydrogen adsorption. Overall, these MOFs are strong candidates for hydrogen storage due to their eco-friendly synthesis and excellent sorption capability compared to previously reported MOF materials. • Two MOFs, Zn 4 O(BDC) 3 and Cu 3 (BTC) 2 , were successfully synthesized using an innovative and sustainable sol-gel method. • Zn 4 O(BDC) 3 achieved a remarkable H 2 uptake of 5.38 wt.% at 77 K and higher than Cu 3 (BTC) 2 at high pressures. • QTAIM concluded that H 2 adsorption occurs through electrostatic interactions. • The Hydrogen storage capacity of Zn 4 O(BDC) 3 and Cu 3 (BTC) 2 demonstrates their strong potential as H 2 storage materials.