Pore-Engineered Non-Noble Metal-Incorporated ZIF-67 as a Dual-Function Catalyst for Hydrogen Generation from Ammonia Borane and Ammonia Mitigation

This study presents the development of a metal-dispersed zeolitic imidazolate framework (ZIF) as a cost-effective and excellent catalyst for hydrogen generation through ammonia borane (AB) hydrolysis. A modified synthesis strategy yielded ZIF-67 with a significantly enhanced surface area of 2100 m 2 g –1 . The optimized Cu@ZIF-67 catalyst showed a remarkably low activation energy of 15.63 kJ mol –1 and a higher turnover frequency (TOF) of 264.1 min –1, surpassing many noble-based catalysts. The combination of X-ray photoelectron spectroscopy (XPS), nitrogen gas sorption study, and positron annihilation lifetime spectroscopy (PALS) analysis, along with density functional theory (DFT) study, revealed the selective interaction of Ni and Cu upon incorporation in ZIF-67. While Ni 2+ gets inserted in the ZIF-67 framework structure by replacing some of the Co 2+ ions, Cu 2+ gets incorporated as metallic Cu within the cavity, enhancing catalytic activity and inducing selective blocking of pores in ZIF-67. DFT calculations further supported the structural variation and kinetic isotope effect (KIE) findings by specifying the O–H bond activation upon coordination with the metallic Cu site. In addition to promoting hydrogen release, Cu@ZIF-67 also acts as an ammonia scavenger, addressing a key challenge in hydrogen production through AB hydrolysis. These findings highlight Cu@ZIF-67 as a durable, cost-effective, and multifunctional catalyst for clean hydrogen production for fuel cell applications. The present experimental finding, along with first-principles calculations, uncovered critical insights into the porous architecture and metal–framework interactions within zeolitic imidazolate frameworks and identified the key descriptor for its excellent catalytic efficacy in the hydrolysis of ammonia borane.