A stable turn-off fluorescence sensor for nitroaromatic explosives and Fe3+ detection based on a 3D strontium coordination polymer

A Sr(II)-based coordination polymer, namely [Sr3(BPTC)1.5(H2O)6.5]n (1), has been constructed by reaction of SrCl2·6H2O and biphenyl-3,3′,5,5′-tetracarboxylic acid (H4BPTC) under hydrothermal condition. X-ray crystallographic analysis indicates that 1 exhibits a 3D framework with I1O2 type. Fluorescence studies show that polymer 1 can detect Fe3+ ion in H2O and 4-nitrophenol (4-NP) in DMF through luminescence quenching. It can serve as a bifunctional luminescent sensor with fast response, good recyclability, high selectivity and sensitivity. The sensing mechanism for Fe3+ can be explained by the synergistic competitive absorption and coordination interactions between Fe3+ and the framework, while the mechanism for detecting 4-NP is mainly attributed to the competitive absorption between the excitation/emission of 1 and analytes.