NH2-MIL-53(Al) Metal–Organic Framework as the Smart Platform for Simultaneous High-Performance Detection and Removal of Hg2+

The worsening pollution due to mercury species makes it inevitable to explore prospective versatile materials, which not only can detect mercury ions (Hg²⁺) with high sensitivity but also possesses efficient capture and removal ability. In this study, a series of classic organic ligand-based luminescence MOFs materials with high oxidation state central metals (Al³⁺, Zr⁴⁺, Cr³⁺, Fe³⁺, and Ti⁴⁺) were synthesized and were screened to achieve simultaneously Hg²⁺ detection and removal through the strong coordination of amino groups or nitrogen centers with Hg²⁺ and the intrinsic fluorescence intensity of MOFs regulated by the ligand-to-metal charge transfer (LMCT) effect. Among these checked materials, NH₂-MIL-53(Al) exhibited the excellent ability for Hg²⁺ detection with wide response interval (1-17.3 μM), low detection limit (0.15 μM), good selectivity, wide pH adaptation (4.0-10.0), and strong anti-interference ability. Meanwhile, the resultant NH₂-MIL-53(Al) possessed an efficient removal capability toward Hg²⁺, accompanied by a fast uptake kinetics (within 60 min) and large loading capacity (153.85 mg g^-1). Furthermore, NH₂-MIL-53(Al) also displayed satisfactory stability before and after Hg²⁺ treatment because of the formation of strong coordination bonds between high oxidation state aluminum (Al³⁺) and organic carboxylate ligands. Notably, the prepared NH₂-MIL-53(Al) had no significant loss of adsorption performance even after being reused four times. All of these superior properties render the smart NH₂-MIL-53(Al) nanohexahedron a great potential for simultaneous Hg²⁺ detection and removal from water.