Computational tuning of the paddlewheel tcb-MOF family for advanced methane sorption

Abstract

A series of metal-organic frameworks (MOFs) with tcb net topology and linkers of increasing size (combining triple bonds and benzene rings) is computationally designed using molecular mechanics and density functional theory. By grand canonical Monte Carlo simulations, we identify MOFs with outstanding methane total uptakes and working capacities, satisfying the targets of the U.S. Department of Energy for automobile applications in cold weather regions (50 wt %, 263 cm3(STP)cm-3). For example, the 5B MOF achieves at 298 K working capacities of 52.2 wt % at 5-65 bar and 61.9 wt % at 5-80 bar. The 3B MOF exhibits at 298 K the most balanced (gravimetric versus volumetric) total uptake and working capacity in the family of tcb-MOFs: 28.4 wt %, 160.9 cm3(STP)cm-3 at 35 bar and 23.0 wt %, 130.3 cm3(STP)cm-3 at 5-35 bar (exceeding the benchmarks of IRMOF-6, PCN-14, Ni-MOF-74, Al-soc-MOF-1, MOF-5, MOF-205), 38.4 wt %, 218.0 cm3(STP)cm-3 at 65 bar and 33.0 wt %, 187.5 cm3(STP)cm-3 at 5-65 bar (exceeding the benchmarks of IRMOF-6, PCN-14, Ni-MOF-74, HKUST-1, NU-111, NOTT-101a), 41.6 wt %, 235.9 cm3(STP)cm-3 at 80 bar and 36.2 wt %, 205.3 cm3(STP)cm-3 at 5-80 bar (exceeding the benchmarks of Ni-MOF-74, MOF-5, MOF-205, HKUST-1).