Anion-templated assembly of three metal-organic frameworks with diverse structures for highly selective detection of Cr2O72- and Fe3+ in aqueous solution

Three novel Pb-II metal-organic frameworks based on 5-methylnicotinic acid have been successfully synthesized under solvothermal condition. HMNA and Pb(OAc)(2) can be assembled to generate a three-dimensional framework of [Pb(MNA)(2)](n) (complex 1). The Pb(OAc)(2) was replaced by Pb(NO3)(2) as the metal source to fabricate a two-dimensional network of [Pb(NO3)(MNA)(n) (complex 2). Meanwhile, PbCl2 also can be coordinated with HMNA to construct a two-dimensional structure of [pb(2)Cl(4)(MNA)](n) (complex 3). The structural diversities of these complexes 1-3 exhibited that the metal-dependent anion effect plays a significantly important role to regulate structures. More importantly, complex 1 was selected as a research mode to investigate its potential luminescent detectability for Cr2O72- and Fe3+ in aqueous solution, which displayed excellent stability and good recyclability at least four times.