Design of robust rod-packing [In(OH)(BDC)] frameworks and their high CO2/C2-hydrocarbons over CH4 separation performance

Abstract The CO2/C2-hydrocarbons over CH4 separation processes are important for the purification of methane fuel. Towards to this purpose, we have designed two isostructural indium-terephthalate metal-organic frameworks (MOFs) decorated with inorganic OH− anions and/or organic –OH Lewis basic groups, namely SNNU-120 and -121. One-dimensional (1D) [In(OH)(COO)2] chains act as rod-shaped secondary building units (SBUs) linking adjacent four SBUs to form robust 3D rod-packing architecture with two types of 1D channels. Under 273 and 298 K, SNNU-120 and -121 have remarkable CO2, C2H2 and C2H4 uptakes but negligible CH4 adsorption. IAST calculations indicate both of them can effectively separate CO2/C2-hydrocarbons from CH4. The gas adsorption and separation performance of inorganic OH− and organic –OH group co-functionalized SNNU-121 MOF are superior to SNNU-120 only with inorganic OH− anions. Specially, the excellent IAST CO2/CH4 (214.4) and C2H4/CH4 (200) selectivity values for SNNU-121 are considered top-level among all rod-packing MOFs and also surpass the values of most famous MOF materials up to now.