Carboxylate-Hydrazone Mixed-Linker Metal-Organic Frameworks: Synthesis, Structure, and Selective Gas Adsorption

New mixed-linker metal-organic framework (MOF) materials incorporating both carboxylate and hydrazone linkers were prepared. The zinc-based 3D MOFs were obtained by utilizing a presynthesized aroylhydrazone [4-pyridinecarbaldehyde isonicotinoyl hydrazone (PCIH)1 and para-dicarboxylic acids [1,4-benzenedicarboxylic acid (H2BDC) and 4,4'-biphenyldicarboxylic acid (H2BPDC)]. Single-crystal X-ray diffraction revealed the interpenetrated, pillar-layered structures of the MOFs, including layers formed by dicarboxylate-bridged Z(n)2 nodes as well as hydrazone pillars. The microporous [Zn-2(dcx)(2)(hdz)(2)]center dot guests frameworks (dcx = linear dicarboxylate dianion; hdz = hydrazone) were found to adsorb CO2 selectively over N-2 upon thermal activation. The frameworks represent rare MOFs of the type [Zn-2(dcx)(2)(pil)(2)] (pil = neutral pillar), in which two pillars at each metallic site of the Zn2 node connect adjacent layers.