Structural optimization of two isoreticular pillared-layer metal-organic frameworks to pore-size-dependent catalytic activity and selective CO2/N2 affinity

Among different type of MOFs, Pillar-layered Metal Organic Frameworks (PMOFs) [1] are widely studied due to their simple fabrication and structural diversity. Herein, we have synthesized a novel pillared-layer MOF, [Zn(L1)(NH2-bdc)].0.5DMF (TMU-52) by incorporating two different organic linkers, namely 2-aminoterephthalic acid as an oxygen-donor linker and L1 (N4,N4 -bis(pyridin-4-ylmethylene)-phenyl-4,4 -diamine) as a long pillaring linker. The structure of this framework which is isoreticular to our recently reported TMU-25, [Zn(NH2-bdc)(L2)].2DMF, was analyzed using X-ray crystallography, FT-IR spectroscopy, Thermogravimetric and elemental analyses. These two metal-organic frameworks are interesting candidates for comparative size selective catalytic performances. In spite of having the same network topology, the pillaring linkers are different in length and subsequently they provide different frameworks with different pore sizes. The selectively of TMU-52 toward different substrate, as a heterogeneous catalyst in aldol-type condensation reaction was significantly higher than TMU-25.