A Simple and Rational Approach for Binodal Metal–Organic Frameworks with Tetrahedral Nodes and Unexpected Multimodal Porosities from Nonstoichiometric Defects

The fact that asymmetrically substituted dicarboxylate is capable of forming two different coordination modes is exploited to synthesize a binodal metal–organic framework containing tetrahedral nodes, and thus [H2N­(CH3)2]2[Zn5(hbdc)6(dabco)2] (1) (hbdc =2-hydroxyterephthalate, dabco =1,4-diazabicyclo[2.2.2]­octane) possesses the (8,4)-coordinated fluorite topology. This simple approach is verified by using symmetrically substituted ligand, 2,5-dihydroxyterephthalate to synthesize a uninodal, 4-coordinated net whose tetrahedral nodes lead to the rare lonsdaleite topology. It has been found that 1 readily loses some of the neutral ligand and cations during the activation processes without collapsing the whole framework, and multimodal porosities are observed due to the nonstoichiometric defects.研究利用不对称取代二羧酸盐可形成两种不同配位模式的特性，合成了一种含四面体节点的双节点金属有机框架（metal–organic framework）。其中化合物1为[二甲基铵]₂[Zn₅(hbdc)₆(dabco)₂]，其中hbdc为2-羟基对苯二甲酸根（2-hydroxyterephthalate），dabco为1,4-二氮杂双环[2.2.2]辛烷（1,4-diazabicyclo[2.2.2]octane），该框架具有(8,4)配位萤石拓扑结构。 本研究通过使用对称取代配体2,5-二羟基对苯二甲酸根合成单节点4配位网络，验证了该简易合成策略的可行性：该网络的四面体节点可形成罕见的蓝丝黛尔石（lonsdaleite）拓扑结构。 研究发现，化合物1在活化过程中可轻易脱除部分中性配体与阳离子，但整体骨架不会发生坍塌；由于存在非化学计量缺陷，该框架呈现出多模态孔隙特性。