Cobalt-engineered zeolitic imidazolate hexagonal nanocrystals as a robust and sustainable catalyst for hydrogen production <i>via</i> NaBH₄ hydrolysis: experimental and theoretical validation

The global economic growth mainly depends on energy consumption, with fossil fuels being a major contributor to environmental concerns. Hydrogen energy can be a greener replacement for future energy requirements. Herein, Co@ZIF was used as an efficient catalyst for hydrogen generation <i>via</i> NaBH₄ hydrolysis. A facile strategy assisted the synthesis of Co@ZIF-<i>X</i> materials through the wet chemical route with reaction times of 60, 90, 120, 150, and 180 min for <i>X</i> = 1, 2, 3, 4, and 5, respectively. The Co@ZIF-5 catalyst showed superior catalytic activity for hydrogen generation <i>via</i> the hydrolysis of NaBH₄ under ideal reaction conditions. This catalyst was optimized by studying the effect of catalyst amount, reaction time, temperature, and NaBH₄ amount. Co@ZIF-5 catalyst demonstrated a high catalytic activity towards the hydrogen evolution reaction and produced 2701 mL of hydrogen w.r.t. a rateof 1350.5 mL min^-1 g^-1 in 80 min at room temperature. Interestingly, Co@ZIF-5 achieved efficient catalytic activity at a low activation energy of 14.95 kJ mol^-1. Furthermore, the Co@ZIF-5 catalyst could be successfully recycled for up to 5 consecutive cycles without significant loss of activity. Theoretical calculations were also performed to assess hydrolysis results and crystal structure validation. This protocol demonstrated that Co@ZIF is a promising catalyst for hydrogen generation under green and sustainable conditions.