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 (H 2 BDC) and 4,4′‐biphenyldicarboxylic acid (H 2 BPDC)]. Single‐crystal X‐ray diffraction revealed the interpenetrated, pillar‐layered structures of the MOFs, including layers formed by dicarboxylate‐bridged Zn 2 nodes as well as hydrazone pillars. The microporous [Zn 2 (dcx) 2 (hdz) 2 ] · guests frameworks (dcx = linear dicarboxylate dianion; hdz = hydrazone) were found to adsorb CO 2 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 Zn 2 node connect adjacent layers.