Functional mesoporous metal-organic frameworks for the capture of heavy metal ions and size-selective catalysis

By using Zn(4)O(CO(2))(6) as secondary building units (SBUs) and two extended ligands containing amino functional groups, TATAB and BTATB (TATAB = 4,4',4''-s-triazine-1,3,5-triyltri-p-aminobenzoate and BTATB = 4,4',4''-(benzene-1,3,5-triyltris(azanediyl))tribenzoate), two isostructural mesoporous metal-organic frameworks (MOFs) with cavities up to 2.73 nm, designated as PCN-100 and PCN-101 (PCN represents porous coordination network), have been synthesized. N(2) sorption isotherms of both PCN-100 and -101 showed typical type IV behavior, indicating their mesoporous nature. The TATAB ligand that comprises PCN-100 was employed to capture heavy metal ions (Cd(II) and Hg(II)) by constructing complexes within the pores with a possible coordination mode similar to that found in aminopyridinato complexes. This reveals that mesoporous materials such as PCN-100 can be applied in the elimination of heavy metal ions from waste liquid. In addition, both PCNs-100 and -101 exhibit size-selective catalytic activity toward the Knoevenagel condensation reaction.