Synergistic effect of hydrogen spillover and nano-confined AlH3 on room temperature hydrogen storage in MOFs: By GCMC, DFT and experiments

Abstract

In order to enhance the hydrogen storage capacity of Metal-Organic Frameworks (MOFs) under moderate conditions, a high-throughput screen was used to evaluate 7622 MOFs with a Pore Limit Diameter (PLD) greater than 2.89 Å and less than 10 Å. The hydrogen adsorption capacity at 25 °C and 1 bar was calculated using grand canonical Monte Carlo (GCMC) to comprehensively evaluate the effect of pore structure characteristics on the hydrogen storage capacity of MOFs. The optimal composite mass ratio between carbon-based materials, transition metals, and MOFs was determined by Density Functional Theory (DFT). The mechanism of hydrogen spillover affecting the hydrogen storage capacity of MOFs was analyzed by preparation, characterization, and hydrogen adsorption capacity testing. To further enhance the hydrogen storage capacity of MOFs composites and improve the kinetic properties and reversibility of metal hydrides, aluminum hydride (AlH3) was nano-confined in MOF@carbon matrix material@transition metal to form new nano-confined composites with improved dehydrogenation temperature and reduced reversibility conditions. The results showed that MOFs with a PLD in the range of 7–10 Å, porosity in the range of 0.75–0.90, and pore volume in the range of 1.4–2.2 cm3/g possess high hydrogen storage capacity. Compared to pristine MOFs, the hydrogen storage capacity of the composites with induced hydrogen spillover is at least 5 times higher. The new composites with improved kinetic hydrogen release characteristics after nano-confined AlH3 achieve reversible hydrogen release at 150 °C and 70 bar.