Catalytic Hydrogen Generation through Ammonia Borane Hydrolysis Using Metal-Organic Framework via O-H Bond Activation

Though ammonia borane (AB) is considered as one of the potential hydrogen storage materials, the effective and economical utilization of AB hydrolysis for efficient hydrogen release encounters hindrances primarily due to the unavailability of an appropriate catalyst. Herein, we present a solvothermal route for synthesizing a series of MOFs and demonstrate superior hydrogen (H-2) production via AB hydrolysis using the optimized Cu-MOF-74 catalyst with an activation energy of 32.1 kJmol(-1) and a turnover frequency (TOF) of 26 min(-1). The influence of ions, AB, and catalyst concentration variation on the rate of AB hydrolysis reaction was investigated. The kinetic isotopic experiment unveils the pivotal step in ammonia borane hydrolysis as the breaking of the O-H bond. Isotope-labeling mass spectrometry techniques were employed to determine the origin of hydrogen and elucidate the underlying reaction mechanism. Interestingly, significant uptake of ammonia by Cu-MOF-74 during hydrolysis of AB can be promising in safeguarding fuel cells. Based on our findings, Cu-MOF-74 catalyst emerges as a dual performer enabling simultaneous hydrogen generation from AB and ammonia capture.