Highly selective and sensitive dual-fluorescent probe for cationic Pb2+ and anionic Cr2O72−, CrO42− contaminants via a powerful indium−organic framework

Lead and chromium, indispensable raw materials, are extensively used in industrial/agricultural production. However, the subsequent Pb(II) and Cr(VI) cause severe issues in biological and environmental safety. Effective detection of Pb(II) and Cr(VI) ions in water is highly desirable, but the existing approaches exhibit high cost and time consuming et al. It is thus extremely urgent to quest for an alternative solution for addressing this issue. Ionic luminescent metal-organic frameworks (iLMOFs) have been regarded as promising optical sensors due to their inherent features of quick response, good selectivity, high sensitivity and cost effective. Regretably, most iLMOFs just response to oppositely charged analytes, perform defective detection limit and recyclability, which dramatically impede their applications. Inspired by our previously reported an anionic indium-based MOF, which could photodegrade organic dyes through both anionic and cationic dyes as photosensitizers located interior and exterior MOF framework, respectively, herein the In-MOF of 1 was successfully deployed as optical sensor to probe Pb(II) and Cr(VI). Remarkably, the highly fluorescent material performs excellently selective and sensitive quenching response towards Pb2+, Cr2O72− and CrO42− in aqueous solution associated with the detection limits of 31.4, 1.2 and 0.52 ​ppb, respectively, all of which are the smallest values among all reported MOFs. The possible fluorescence emission and quenching mechanisms of 1 were tentatively proposed. Moreover, the inspiring quantitative detection ability of 1 towards Cr(VI) have also been ensured by flawlessly maintained in 7 successive detection cycles, providing the prerequisite in practical applications.