Hydrothermal Syntheses of Metal–Organic Frameworks Constructed from Aromatic Polycarboxylate and 4,4′-Bis(1,2,4-triazol-1-ylmethyl)biphenyl

Six new metal–organic frameworks, namely, {[Co(btmb)(HBTC)]·2H2O}n (1), {[Co3(btmb)3(BTC)2(H2O)2]·6H2O}n (2), {[Co3(btmb)3(BTC)2(H2O)4]·2H2O}n (3), {[Ni3(btmb)3(BTC)2(H2O)4]·2H2O}n (4), [Cu(btmb)(HBTC)]n (5), and [Cu(btmb)(NDC)]n (6) (H3BTC = 1,3,5-benzenetricarboxylic acid, H2NDC = 1,2-benzenedicarboxylic acid, and btmb = 4,4′-bis(1,2,4-triazol-1-ylmethyl)biphenyl), have been synthesized under hydrothermal conditions. The structure of 1 is a 6-connected self-penetrating three-dimensional (3D) framework with 44·610·8 topology. Complex 2 exhibits a trinodal (3,4)-connected topology with a Schläfli symbol of (62·84)(64·82)(63). Both complexes 3 and 4 possess 3D pillar-layered structures with a Schläfli symbol of (62·8·103)(64·8·10)(6·102). Complex 5 is also a 3D polymer with a pillar-layered framework, which can be simplified as the (63)(69·8) topology. Complex 6 shows a 4-connected 3D framework with a Schläfli notation of (65·8)2. Furthermore, complexes 1–6 as heterogeneous catalysts were studied in the green catalysis process of the oxidative coupling of 2,6-dimethylphenol (DMP) to poly(1,4-phenylene ether) (PPE) and diphenoquinone (DPQ). The results show that these complexes exhibit different catalytic activities; both the Cu complexes are catalytically active by showing high conversion of DMP and high selectivity of PPE, and they exhibit great potential as recyclable catalysts.

本研究通过水热法合成了六种新型金属-有机框架（metal–organic frameworks），分别为{[Co(btmb)(HBTC)]·2H₂O}ₙ(1)、{[Co₃(btmb)₃(BTC)₂(H₂O)₂]·6H₂O}ₙ(2)、{[Co₃(btmb)₃(BTC)₂(H₂O)₄]·2H₂O}ₙ(3)、{[Ni₃(btmb)₃(BTC)₂(H₂O)₄]·2H₂O}ₙ(4)、[Cu(btmb)(HBTC)]ₙ(5)与[Cu(btmb)(NDC)]ₙ(6)。其中，H₃BTC代表1,3,5-苯三甲酸，H₂NDC代表1,2-苯二甲酸，btmb代表4,4'-双(1,2,4-三唑-1-基甲基)联苯。
化合物1的结构为具有4⁴·6¹⁰·8拓扑的6连接自穿插三维（3D）骨架。化合物2呈现三节点(3,4)连接拓扑，其施莱夫利符号（Schläfli symbol）为(6²·8⁴)(6⁴·8²)(6³)。化合物3与4均具有三维柱层状结构，其施莱夫利符号为(6²·8·10³)(6⁴·8·10)(6·10²)。化合物5同样为具备柱层状骨架的三维聚合物，可简化为(6³)(6⁹·8)拓扑。化合物6呈现4连接三维骨架，其施莱夫利符号为(6⁵·8)²。
此外，本文将化合物1至6作为非均相催化剂，用于2,6-二甲基苯酚（2,6-dimethylphenol, DMP）氧化偶联合成聚(1,4-亚苯醚)（poly(1,4-phenylene ether), PPE）与联苯醌（diphenoquinone, DPQ）的绿色催化体系开展研究。研究结果显示，上述配合物展现出各异的催化活性：其中两种铜基配合物均表现出优异的催化性能，对DMP具有高转化率且对PPE选择性优异，具备作为可回收催化剂的巨大应用潜力。