Efficient removal and sensing of copper(II) ions by alkaline earth metal-based metal–organic frameworks

A class of alkaline earth metal-based metal–organic frameworks (MOFs), namely NDCMOF(Ca) and NDCMOF(Sr), has been synthesized using 2,6-naphthalenedicarboxylic acid (NDC) as the linker. In view of the biocompatibility of the starting materials, these MOFs are expected to be environmentally benign and, in this work, have been employed for the removal of copper(II) ions (Cu2+) from aqueous systems. The results showed that the maximum adsorption capacities of NDCMOF(Ca) and NDCMOF(Sr) for Cu2+ were 299.4 and 398.4 ​mg ​g−1, respectively, which were comparable to those of related MOFs and porous materials. Meanwhile, NDCMOF(Ca) and NDCMOF(Sr) displayed blue luminescence in the solid state at room temperature upon photoexcitation with ultraviolet (UV) light. This emission would be readily quenched after the adsorption of Cu2+ ions. Such visible changes in the observed color and emission of the MOFs have rendered them versatile adsorbents and sensors for Cu2+ in the aqueous environment. A class of biocompatible alkaline earth metal-based metal–organic frameworks (MOFs) has been synthesized and characterized. These MOFs can function as efficient adsorbents as well as sensors for copper(II) ions in the aqueous environment. [Display omitted] •A series of alkaline earth metal-based MOFs was synthesized for the adsorptive removal of copper(II) ions from water.•The strontium MOF, namely NDCMOF(Sr), exhibited an excellent copper(II) adsorption capacity of 398.4 ​mg ​g−1.•The MOFs could also function as effective luminescence sensors for copper(II) with instantaneous responses.