Porous Interpenetrating Metal−Organic Frameworks with Hierarchical Nodes

We present the solvothermal syntheses, X-ray crystal structures, and gas sorption properties of a series of zinc−dicarboxylate−polypyridine where the dicarboxylate is 1,4-benzenedicarboxylate, 4,4′-biphenyldicarboxylate, or sulfone-4,4′-biphenyldicarboxylate and the polypyridine is bipyridine or 1,4-bis(4-pyridylethynyl)benzene. The structures consist of hierarchical two-, three-, and four-blade dimer or trimer nodes which generate the square or triangular topologies of the metal-carboxylate layers which are pillared by the bipyridine. Two- and 3-fold interpenetration of frameworks was observed depending on the length of both the carboxylate and the bipyridine. In all cases, the structure sustains a variable degree of space within the metal−organic frameworks where solvents are located. The solvents are easily lost and the structures display accessible voids where adsorption of other gases can be realized. The present set of compounds reveals a picture that does not conform to the current belief that interpenetration of lattices results in highly compact structures.本工作报道了一系列锌-二羧酸酯-多吡啶配合物的溶剂热合成（solvothermal syntheses）、X射线晶体结构（X-ray crystal structures）与气体吸附性能（gas sorption properties），所用二羧酸酯配体包括对苯二甲酸根（1,4-benzenedicarboxylate）、4,4'-联苯二甲酸根（4,4′-biphenyldicarboxylate）及砜基-4,4'-联苯二甲酸根（sulfone-4,4′-biphenyldicarboxylate），多吡啶配体则为联吡啶（bipyridine）或1,4-二(4-吡啶乙炔基)苯（1,4-bis(4-pyridylethynyl)benzene）。该系列配合物的结构由层级化二叶、三叶及四叶状二聚体或三聚体节点构成，此类节点构筑出金属-羧酸酯层的方形或三角形拓扑结构，该层由联吡啶进行柱撑。根据二羧酸酯配体与联吡啶的链长差异，配合物的金属有机框架（metal−organic frameworks）可呈现二重与三重穿插结构。所有配合物的金属有机框架内部均存在一定占比的溶剂占位空间，溶剂极易脱除，该类框架展现出可访问孔穴，可实现其他气体的吸附。本系列化合物的研究结果表明，当前学界认为晶格穿插会导致结构高度致密的认知与实际情况不符。