Stability and Porosity Enhancement through Concurrent Ligand Extension and Secondary Building Unit Stabilization

A trigonal nanosized carboxylate ligand, 1,3,5-tris[4‘-carboxy(1,1‘-biphenyl-4-yl)]benzene (TCBPB), has been synthesized and applied in the construction of porous metal−organic frameworks (MOFs). A solvothermal reaction of TCBPB and a zinc salt in the presence of pyridine produces 1, an unstable MOF consisting of a tetrazinc secondary building unit (SBU) with labile terminal ligands. Changing pyridine to a noncoordinating base in the assembly procedure affords 2, a stable MOF with permanent porosity containing an octazinc SBU without labile terminal ligands.本研究合成了一种三角纳米级羧酸配体——1,3,5-三[4'-羧基(1,1'-联苯-4-基)]苯（1,3,5-tris[4‘-carboxy(1,1‘-biphenyl-4-yl)]benzene，TCBPB），并将其应用于多孔金属有机框架（porous metal−organic frameworks, MOFs）的构建。 将TCBPB与锌盐在吡啶存在的条件下进行溶剂热反应，可得到化合物1——一种由含易解离末端配体的四锌次级结构单元（secondary building unit, SBU）构成的不稳定金属有机框架。在组装过程中将吡啶替换为非配位碱，则可得到化合物2——一种具备永久孔隙率的稳定金属有机框架，其结构包含不含易解离末端配体的八锌次级结构单元（SBU）。