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.