Structural Isomerism and Effect of Fluorination on Gas Adsorption in Copper-Tetrazolate Based Metal Organic Frameworks

Synthesis, structure, and gas adsorption properties of three Metal Organic Frameworks (MOFs) synthesized from predesigned ligands 4-(1 H -tetrazole-5-yl)benzoic acid ( 4-TBA ) and 2-fluoro-4-(1 H -tetrazole-5-yl)benzoic acid ( 2F-4-TBA ) along with Cu(II) as an metal precursor has been reported. Among these MOFs, Cu 9 (4-TBA) 10 (C 2 H 5 OH) 2 ( Cu-TBA-1 ) and Cu 2 (4-TBA) 2 (DMF)(C 2 H 5 OH) ( Cu-TBA-2 ) are structural isomers. Whereas, Cu 2 (4-TBA) 2 (DMF)(C 2 H 5 OH) ( Cu-TBA-2 ) and Cu 2 (2-F-4-TBA) 2 (DMF) 2 ( Cu-TBA-2F ) have similar crystal structure. N 2 adsorption isotherms of the activated sample of Cu-TBA-1 and -2 exhibit types-I sorption behavior with a Langmuir and Brunauer–Emmett–Teller (BET) surface area of 686, 402 m 2 /g and 616, 356 m 2 /g, respectively. It is noteworthy that Cu-TBA-1 and -2 adsorbs 1.16 and, 1.54 wt % H 2, while Cu-TBA-2F adsorbs 0.67 wt % at 77 K and 1 atm. On the other hand, Cu-TBA-1 and -2 adsorb 3.08 and 2.54 mmol/g, while Cu-TBA-2F adsorbs 1.27 mmol/g of CO 2 at 298 K and 1 bar pressure. H 2 adsorption sites in Cu-TBA-2 and -2F have been analyzed by molecular simulation.