Hydrogen storage properties of the novel crosslinked UiO-66-(OH)(2)

Metal organic frameworks (MOF) are a type of nanoporous materials with large specific surface area, which are especially suitable for gas separation and storage. In this work, we report a new approach of crosslinking UiO-66-(OH)(2) to enhance its hydrogen storage capacity. UiO-66-(OH)(2) was synthesized using hafnium tetrachloride (HfCl4) and 2, 5-dihydroxyterephthalic acid (DTPA) through a canonical modulated hydrothermal method (MHT), followed by a post -synthesis modification, which is to form a crosslinking structure inside the porous structure of UiO-66-(OH)(2). During the modification process, the phenolic hydroxyl groups on the UiO-66-(OH)(2) reacted with methanal, and HCl aqueous solution and triethylamine served as catalyst (the products denoted as UiO-66-H and UiO-66-T, respectively). Powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FT-IR), C-13 nuclear magnetic resonance spectroscopy (C-13 NMR) proved that the cross linking was formed. The BET specific surface area and the average adsorption pore size of UiO-66-H and UiO-66-T significantly increased after modification. The hydrogen storage capacity of UiO-66-H reached a maximum of 3.37 wt% (16.87 mmol/g) at 77 K, 2 MPa. Hydrogen adsorption enthalpy of UiO-66-T was 0.986 kJ/mol, which was higher than that of UiO-66-(OH)(2) (0.695 kJ/mol). This work shows that UiO-66-(OH)(2) is a promising candidate for potential application in high-performance hydrogen storage. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.