(25c) Linker Functionalization In Metal-Organic Frameworks for Enhanced Ambient Temperature Hydrogen Storage

Developing alternative energy sources is one of the primary challenges in chemical engineering research today. Hydrogen is attractive because it has a high gravimetric energy density, it is non-toxic, and its oxidation product is water. However, difficulties in production, infrastructure development, and storage currently impede expansion of the hydrogen economy. In this work we use quantum chemical calculations in coordination with grand canonical Monte Carlo simulations to examine molecular hydrogen storage in metal-organic frameworks (MOFs). MOFs, which are crystalline materials comprised of metal or metal oxide nodes connected with organic ?linker? molecules, are permanently porous and have high surface areas, ideal for gas adsorption. Additionally, the corners and linkers can be optimized for a variety of uses. Here we show how metal alkoxide functionalization in the linkers, an experimentally realizable strategy, enables significant ambient temperature hydrogen storage. We examine a variety of alkali, alkaline earth, and transition metals, and predict heats of adsorption from 10 ? 80 kJ/mol (to be compared with heats in non-functionalized MOFs of 3 ? 15 kJ/mol). We explore ambient temperature hydrogen storage in a variety of MOFs and propose design criteria to meet DOE onboard hydrogen storage targets.