Synthesis of tricarboxylic acid based metal organic frameworks: Structural and gas adsorption studies

Abstract Two folded interpenetrating metal organic frameworks (MOFs) viz. {[Zn4(L)2(NO3)(H2O)3]+ [S1]}n (LZn) and {[Cd4(L)2(NO3)(DMF)8(H2O)](NO3)(DMF)2(S2)}n (LCd) where S1 denotes squeezed nitrate anions and solvent molecules and S2 denotes the squeezed solvent molecule, have been synthesized from (4,4′,4′'-(((2,4,6-trimethylbenzene-1,3,5-triyl)tris(methylene))tris(azanediyl))tribenzoic acid) (H3L) ligand and Zn(NO3)2•6H2O/Cd(NO3)2•4H2O metal salts by solvothermal process. The structural analysis showed that both LZn and LCd are two dimensional (2D) interpenetrating metal organic frameworks containing binuclear paddle wheel secondary building units (SBUs), Zn2(COO)3 and Cd2(COO)3, with hexagonal (hcb) net topology having 3-connected uninodal net. In LZn, both interpenetrating frameworks are vertical while in LCd, these are parallel to each other. Thermogravimetric analysis showed that both MOFs are stable up to 350 °C. Gas adsorption study demonstrated that these MOFs are selective towards CO2 over N2 gas due to sieving effect as well as Lewis acid-Lewis base interaction.