Auxiliary ligand-modulated trisimidazole-based coordination polymers: syntheses, structures and photoluminescence properties

Five coordination polymers having 1,3,5-tris(1-imidazolyl)benzene and the varied O-donor auxiliary ligands were designed and synthesized. Further, the auxiliary ligands modulated these complexes with structural diversities and novel topologies.

Integrating cationic metal-organic frameworks with ultrafiltration membrane for selective removal of perchlorate from Water

We design a novel cationic metal-organic framework hybrid ultrafiltration polyvinylidene fluoride membrane (PVA/Cu-iMOFs/PVDF-0.05) and report its unique capture of aqueous perchlorate (ClO₄^-) at ppm-level. This membrane outperformed traditional adsorption materials and exhibited a specific affinity toward ClO₄^- in the presence of various competing anions at greater levels (up to a concentration ratio of 20). In the batch experiment, the ClO₄^- removal ratio reached 99.6% over a wide pH range (3˜10). Membrane filtration by using a 12.56 cm² PVA/Cu-iMOFs/PVDF-0.05 membrane could effectively treat 4.71 L of ClO₄^--contaminated water before breakthrough occurred, while maintaining a satisfactory permeability (˜627.32 L/(m² h bar)) and antifouling property. The exhausted membrane could easily be regenerated in aminoethanesulfonic acid solution for repeated use with a negligible decrease in capacity. Moreover, the membrane showed excellent long-term stability in a cross-flow filtration process due to the amido bond between the Cu-iMOFs and membrane surface as well as the "protection" of polyvinyl alcohol. Selective and reversible ion-exchange between the sulfonic acid (R-SO₃) ligands of Cu-iMOFs and tetrahedral oxo-anionic species was verified to be the pathway for ClO₄^- trapping. Thus, other problematic elements that also occur in tetrahedral form in water can be removed by this method.