Luminescent microporous metal–organic framework with functional lewis basic sites on the pore surface: specific sensing and removal of metal ions

Abstract

A three-dimensional luminescent metal–organic framework, {Mg(DHT)(DMF)₂}_n (1), based on an excited-state intramolecular proton-transfer (ESIPT) responsive linker, 2,5-dihydroxyterephthalic acid (H₂DHT), has been synthesized, and its desolvated microporous framework with pendent −OH groups on the pore surface was exploited for the binding and specific sensing of metal ions via Lewis acid–base interactions. The luminescence intensity significantly quenches with Cu^II among various s- and d-block metal ions, and highly selective sensing of Cu^II ions has been realized in both solid and solution states (up to nanomolar concentration). The immobilized Cu^II metal ions can be selectively removed by chelating agents like ethylenediaminetetraacetic acid without any structural disintegration of the framework, as revealed by the luminescence and gas-adsorption studies.