Syntheses, Structures, and Structural Transformations of Mixed Na(I) and Zn(II) Metal–Organic Frameworks with 1,3,5-Benzenetricarboxylate Ligands

Three new compounds, [ZnNa(BTC)(H2O)2]·H2O (1), [Zn3Na2(BTC)2(HCOO)2(H2O)8] (2), and [Zn3Na(BTC)2(HCOO)(H2O)3]·2H2O (3) (H3BTC = 1,3,5-benzenetricarboxylate acid), were synthesized under hydrothermal conditions and were characterized by the single crystal and powder X-ray diffraction, IR spectra, elemental analyses, ICP measurements, and coupled TG-MS analyses. 1, 2, and 3 crystallize in the space groups P1̅, C2/c, and P1, respectively. They are three-dimensional (3D) frameworks, consisting of zigzag chains ((Na2Zn2O14)n for 1, (Na2Zn3O18)n for 2, or (NaZn3O14)n for 3) and bridging BTC ligands. Powder X-ray diffraction studies reveal that 1 and 2 exhibit reversible dehydration–rehydration behaviors with a crystal-to-crystal transformation observed for 2.本研究通过水热合成法制备得到三种新型配合物：[ZnNa(BTC)(H₂O)₂]·H₂O（1）、[Zn₃Na₂(BTC)₂(HCOO)₂(H₂O)₈]（2）以及[Zn₃Na(BTC)₂(HCOO)(H₂O)₃]·2H₂O（3），其中H₃BTC为1,3,5-苯三甲酸（1,3,5-benzenetricarboxylic acid）。随后采用单晶X射线衍射、粉末X射线衍射、红外光谱、元素分析、电感耦合等离子体（ICP）测试以及热重-质谱（TG-MS）联用分析对上述三种配合物进行了全面表征。配合物1、2与3分别结晶于P1̅、C2/c及P1空间群。三者均为三维（3D）骨架结构，分别由之字形链（配合物1对应(Na₂Zn₂O₁₄)ₙ、配合物2对应(Na₂Zn₃O₁₈)ₙ、配合物3对应(NaZn₃O₁₄)ₙ）与桥联BTC配体构筑而成。粉末X射线衍射研究结果表明，配合物1和2表现出可逆的脱水-复水行为，其中配合物2还伴随有晶体到晶体的转变过程。