Iron-Decorated, Functionalized Metal Organic Framework for High-Capacity Hydrogen Storage: First-Principles Calculations

We perform ab initio density functional theory calculations to investigate the hydrogen storage capacity in the Fe-decorated, OH-functionalized isoreticular metal organic framework 16. The hydroxyl group (OH) is used as an anchor to hold an Fe atom firmly on the metal organic framework, and the hydrogen molecules are bound to the Fe atom through hybridization with Fe d orbitals. We show that each Fe atom in this modified MOF can bind up to four H-2 molecules with an adequate binding energy for room-temperature storage (similar to 29 kJ/mol). The transition from the high-spin to the low-spin configuration is found to be crucial in enhancing the number of bound H-2 as well as the binding energy. Equilibrium thermodynamics calculations accompanied with grand canonical Monte Carlo simulations give a very promising result, namely, a reversibly usable gravimetric storage density of 6.0 wt % at 298 K and 100 atm.