Group 13 Metal Carboxylates: Using Molecular Clusters As Hybrid Building Units in a MIL-53 Type Framework

Systematic investigation of the reactions of the system AlCl3·6H2O/pyridine-2,4,6-tricarboxylic acid (H3PTC)/pyridine in water yielded two new compounds, both containing the dimeric {AlPTC(μ-OH)­(H2O)}22– unit. With long reaction times, the framework compound [Al­(μ-OH)­{AlPTC(μ-OH)­(H2O)}2]·2H2O (CAU-16, compound 1) is obtained, the first example of a framework compound with a metal–organic cluster linker, and bearing the MIL-53 network. Although the compound does not breathe, as other MIL-53 compounds do, it has a maximum uptake of CO2 of 1.76(2) mmol g–1 at 196 K. With shorter reaction times, the molecular compound {Al­(HPTC)­(μ-OH)­(H2O)}2 (2) was prepared, leading to the proposal of a crystallization scheme for the Al3+-pyridine-2,4,6,-tricarboxylic acid system. To determine whether further framework compounds bearing hybrid metal cluster linkers could be prepared, systematic high-throughput investigations of pyridine-2,4,6-tricarboxylic acid in water with Ga3+ and In3+ were undertaken. These yielded two chain-type compounds, GaPTC(H2O)2 (3) and InPTC(H2O)2 (4), with different coordination chemistries. Optimized syntheses for compounds 1, 2, and 4 are reported.

以水为溶剂，对六水合三氯化铝（AlCl₃·6H₂O）/吡啶-2,4,6-三羧酸（H₃PTC）/吡啶体系的反应进行系统性研究，得到两种全新化合物，二者均含有二聚体{AlPTC(μ-OH)(H₂O)}₂²⁻结构单元。当反应时间较长时，可获得骨架化合物[Al(μ-OH){AlPTC(μ-OH)(H₂O)}₂]·2H₂O（CAU-16，化合物1），这是首例以金属有机簇作为连接基的骨架化合物，其网络结构属于MIL-53型。尽管该化合物不具备其他MIL-53类化合物典型的呼吸效应，但在196 K下其二氧化碳最大吸附量可达1.76(2) mmol·g⁻¹。当反应时间较短时，可制备得到分子化合物{Al(HPTC)(μ-OH)(H₂O)}₂（化合物2），据此提出了Al³⁺-吡啶-2,4,6-三羧酸体系的结晶路径。为探究是否可制备更多带有杂化金属簇连接基的骨架化合物，研究人员对水相中Ga³⁺、In³⁺与吡啶-2,4,6-三羧酸的反应开展了系统性高通量研究。该研究得到两种链状化合物：GaPTC(H₂O)₂（化合物3）与InPTC(H₂O)₂（化合物4），二者具有不同的配位化学特性。本文报道了化合物1、2和4的优化合成方法。