Predicting Methane Storage in Open-Metal-Site Metal–Organic Frameworks

The development of high-capacity methane adsorbents would accelerate the adoption of natural gas as a vehicular fuel, thereby lowering CO2 emissions from the combustion of gasoline. In this regard metal–organic frameworks (MOFs) have emerged as promising methane storage materials due to their high capacities and tunable properties. Within this class, HKUST-1 ([Cu3(BTC)2]n, BTC = 1,3,5-benzenetricarboxylate) is an important benchmark, as it exhibits methane densities that are among the highest reported. Furthermore, uptake in HKUST-1 can potentially be tuned by altering the methane–MOF interaction through metal substitution on coordinatively unsaturated sites (CUS). Predicting the impact of metal substitution remains a challenge, however, because general interatomic potentials commonly used in calculating uptake do not properly describe interactions involving CUS. Here, a new interatomic potential that explicitly accounts for these interactions is derived from quantum-mechanical calculations. The potential...