Zirconium(IV)-Succimer Metal-Organic Framework Functionalized PVDF-HFP Membranes for Heavy-Metals Capture

Although heavy metal contamination is an ancient problem, it remains a global concern in isolated areas. Herein, we report the design of a novel thiol-rich Zr(IV) metal-organic framework (BCM-5), assembled from meso-2,3-dimercaptosuccinic acid (Succimer), a commercially available thiol-rich metal-chelating agent used in the treatment of heavy metal poisoning. BCM-5 has been subsequently integrated into porous PVDF-HFP membranes processed via salt-leaching. The non-immobilized BCM-5 and the BCM-5@PVDF-HFP membranes were systematically evaluated for Pb(II), Cd(II), and Hg(II) capture. The results demonstrate that the metal-chelating functionalities of Succimer linker are effectively preserved within the BCM-5 framework, while immobilization of BCM-5 into PVDF-HFP membranes significantly enhances the material's dispersibility and improves its capacity for the efficient capture of the targeted heavy metals. A detailed structural, chemical, and DFT characterization of post-adsorption BCM-5 suggests that metal immobilization proceeds via chemisorption within hydrophobic, hydrophilic, and amphiphilic pore regions of BCM-5, depending on the nature of the heavy metal. Overall, this work introduces a novel approach to use metal-chelator molecules as building blocks for MOFs construction targeted to the recovery of heavy metals, while also detailing strategies for their immobilization into polymeric structures with interconnected macroporosity.