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)] 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 Zn2 nodes as well as hydrazone pillars. The microporous [Zn2(dcx)2(hdz)2]·guests frameworks (dcx = linear dicarboxylate dianion; hdz = hydrazone) were found to adsorb CO2 selectively over N2 upon thermal activation. The frameworks represent rare MOFs of the type [Zn2(dcx)2(pil)2] (pil = neutral pillar), in which two pillars at each metallic site of the Zn2 node connect adjacent layers.