Favorable Hydrogen Storage Properties of M(HBTC)(4,4′-bipy)·3DMF (M = Ni and Co)

Two metal−organic frameworks of M(HBTC)(4,4′-bipy)·3DMF (M = Ni and Co; H₃BTC = 1,3,5-benzenetricarboxylic acid; 4,4′-bipy = 4,4′-bipyridine; DMF = N,N′-dimethylformamide) were synthesized by a one-pot solution reaction and a solvothermal method, respectively. The as-prepared samples have high specific surface areas of 1590 m²/g and 887 m²/g. The activation at different temperatures for the guest removal prior to gas loading obviously affects the gas sorption process. Ni(HBTC)(4,4′-bipy)·3DMF shows high hydrogen storage capacities of 1.20 wt % at room temperature and 3.42 wt % at 77 K. Co(HBTC)(4,4′-bipy)·3DMF shows capacities of 0.96 wt % at 298 K and 2.05 wt % at 77 K. The hydrogen adsorption heats in the two compounds decrease slightly as a function of the amount adsorbed, and it confirms that the H₂ molecules are combined with stronger sites preferentially. Research on the kinetics of hydrogen adsorption shows a fast saturation process (80 s) and no obvious capacity loss after 20 cycles.