Functional Mesoporous Metal-Organic Frameworks for the Capture of Heavy Metal Ions and Size-Selective Catalysis

By using Zn4O(CO2)(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.