Superparamagnetic Mn-Based MOF as Electrode for Supercapacitors

Metal-organic frameworks (MOFs) are attractive candidates for meeting the needs of next-generation technologies. With a creative and meticulous design strategy, we tried to synthesize a novel Mn-based metal-organic framework with flake-like morphology which was further transformed into a beautiful marigold flower-like MOF. This grafting of MOF on a core substrate enabled us to achieve nanosized MOF with controllable thickness instead of a microsized irregularly shaped flakey MOF. Unlike typical guest encapsulation in MOF cavities, core-shell composites possess superior pore accessibility, ensuring optimal ion diffusion. They also exhibit a unique architecture that prevents the active guest from agglomerating or leaching, while promoting a tight connection between the core and shell, resulting in synergistic effects. This study utilized a sequential growth strategy to synthesize a core-shell hybrid of Fe₃O₄@Mn-MOF-NH₂. This hybrid combines a Mn-based MOF with a metal oxide to achieve both redox hopping and the through-layer mechanism of charge transport in a single system. The synthesized nanohybrid was used as an electrode material for supercapacitors, and its electrochemical properties were investigated. Additionally, these superparamagnetic MOFs can be separated almost instantaneously by applying an external magnetic field. Thus, they can be used easily in many applications like water, wastewater treatment, catalysis, etc. This hybrid MOF composite with multiple functionalities (optical, magnetic, etc.) offers huge potential for a variety of applications and enriches the MOF library. The flowered MOF hybrid design shed light on the micro or nanosized structural design changes or meticulous morphology adjustment of porous MOF composites for property optimization. This study provides an insight for the controllable preparation of MOF hybrid architectures which would further broaden the application opportunities of metal-organic framework materials.