Computational design of tetrazolate-based metal-organic frameworks for CH 4 storage.

CH4 is considered as an environmentally benign fuel and there is considerable interest in the development of new materials for CH4 storage. In this study, 424 tetrazolate-based metal-organic frameworks (MOFs) were computationally designed including 304 structures with the, urr and fcu topological nets and 120 structures with diverse nets. The CH4 deliverable volumetric capacities of all designed nanoporous materials and the adsorption isotherms of the top 10 hypothetical MOFs with high volumetric deliverable capacity at 298 K were predicted using molecular simulations. From the simulation results, tetrazolate blocks adjacent to pyrene or dibenzene linkers in fcu topological MOFs were found to provide lower density CH4 storage at delivery pressure (5.8 bar) as well as more efficient CH4 packing at charge pressure (65 or 35 bar), resulting in an obvious enhancement in CH4 deliverable volumetric capacity. The predicted CH4 deliverable capacity of Zr-fcu-MOF-2Py between 65 and 5.8 bar can reach 177 cm3 (STP) cm-3, the highest among tetrazolate-based MOFs studied. In comparison with NU-Py-fcu (with carboxylate blocks and pyrene linkers), its deliverable capacity increases 45.1% from 122 to 177 cm3 (STP) cm-3 under the same conditions. The enhancement mechanism from microscopic insights provided details on how the incorporation of tetrazolate links into MOFs would affect CH4 adsorption and delivery. This will lead to a novel way to enhance CH4 volumetric delivery capacity through finely tuning the chemical environment of MOFs with the incorporation of polar functional groups such as tetrazolate blocks.