Solvothermal reactions of 3-(4-pyridyl)-benzoic acid (Hpba) with a series of transition metal ions yielded isostructral metal-organic frameworks [M(pba)2]·2DMA (MCF-52; M = Ni2+, Co2+, Zn2+, Cd2+, or mixed Zn2+/Cd2+; DMA = N,N-dimethylacetamide) possessing two-dimensional fence-like coordination networks based on mononuclear 4-connected metal nodes and 2-connected organic ligands. Variable-temperature single-crystal X-ray diffraction studies of these materials revealed huge positive and negative thermal expansions with |α| > 150 × 10−6 K−1, in which the larger metal ions give the larger thermal expansion coefficients, because the increased space not only enhance the ligand vibrational motion and hinged-fence effect, but also allow larger changes of steric hindrance between the layers. In addition, the solid-solution crystal with mixed metal ions further validates the abundant thermal expansion mechanisms of these metal-organic layers.
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机译：3-（4-吡啶基）-苯甲酸（Hpba）与一系列过渡金属离子的溶剂热反应产生同构金属-有机骨架[M（pba）2]·2DMA（MCF-52; M = Ni 2 + ，Co 2 + ，Zn 2 + ，Cd 2 + 或混合的Zn 2 + > / Cd 2 + ; DMA = N，N-二甲基乙酰胺），具有基于单核4-连接金属节点和2-连接有机配体的二维栅栏状配位网络。这些材料的可变温度单晶X射线衍射研究表明，|α|的正负热膨胀很大。 > 150×10 −6 K −1 ，其中较大的金属离子给出较大的热膨胀系数，因为增加的空间不仅增强了配体的振动运动并铰接栅栏效应，但也允许各层之间的空间位阻发生较大变化。另外，具有混合的金属离子的固溶体晶体进一步证实了这些金属-有机层的丰富的热膨胀机理。
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