A new porous coordination polymer reveals selective sensing of Fe3+, Cr2O72−, CrO42−, MnO4− and nitrobenzene, and stimuli-responsive luminescence color conversions

Abstract

A novel one-dimensional spiro-like chain coordination polymer with a blue-emission signal was solvothermally synthesized via the reaction of Zn²⁺ ions with organic ligand HL (4-(4-(2-chloroimidazo[1,2-a]pyridin-3-yl)-[2,3′-bipyridin]-6-yl)benzoic acid), which is further extended to a porous three-dimensional supramolecular framework, namely, the porous coordination polymer (PCP), [Zn(L)₂]·2DMF (USTC-5). This PCP was characterized by IR spectroscopy, thermogravimetry, and single-crystal, and powder X-ray diffraction methods. USTC-5 possesses larger quasi-hexagonal channels with Lewis-base sites, and is a better CO₂ adsorption or promising CO₂/N₂ selective material, suggesting potential application in gas separation. USTC-5 also can serve as a multi-responsive sensing material for detecting Fe³⁺, Cr₂O₇²⁻, CrO₄²⁻, MnO₄⁻ and nitrobenzene (NB). Moreover, the mechanism of the selective luminescence quenching response for Cr₂O₇²⁻, CrO₄²⁻, MnO₄⁻ and NB can be mainly ascribed to the competitive adsorption of excitation wavelength energy between USTC-5 and Cr₂O₇²⁻, CrO₄²⁻, MnO₄⁻ or NB; meanwhile, Fe³⁺ ions diffused into the channels of USTC-5 and formed contacts with Lewis-base sites in USTC-5, leading to luminescence quenching. Significantly, USTC-5 displays reversible luminescence color switching in response to acid–base vapor stimuli, which originates from the conversion between the amorphous form and the crystal mediated by protonation–deprotonation processes. Such a stimuli-responsive conversion provides a promising approach to design and construct smart PCP materials.