Lewis acidic Fe³⁺-driven catalytic active Ni³⁺ formation in Fe-free metal-organic framework for enhanced...

Manipulating metal valence states and porosity in the metal-organic framework (MOF) by alloying has been a unique tool for creating high-valent metal sites and pore environments in a structure that are inaccessible by other methods, favorable for accelerating the catalytic activity towards sensing applications. Herein, we report Fe³⁺-driven formation of catalytic active Ni³⁺ species in the amine-crafted benzene-dicarboxylate (BDC-NH₂)-based MOF as a high-performance electrocatalyst for glucose sensing. This work took the benefit of different bonding stability between BDC-NH₂ ligand, and Fe³⁺ and Ni²⁺ metal precursor ions in the heterometallic Ni_xFe_(1-x)-BDC-NH₂ MOF. The FeCl₃ that interacts weakly with ligand, oxidizes the Ni²⁺ precursor to Ni³⁺-based MOF owing to its Lewis acidic behavior and was subsequently removed from the structure supported by Ni atoms, during solvothermal synthesis. This enables to create mesopores within a highly stable Ni-MOF structure with optimal feed composition of Ni_0.7Fe_0.3-BDC-NH₂. The Ni³⁺-based Ni_0.7Fe_0.3-BDC-NH₂ demonstrates superior catalytic properties towards glucose sensing with a high sensitivity of 13,435 µA mM^-1 cm^-2 compared to the parent Ni²⁺-based Ni-BDC-NH₂ (10897 μA mM^-1cm^-2), along with low detection limit (0.9 μM), short response time (≤5 s), excellent selectivity, and higher stability. This presented approach for fabricating high-valent nickel species, with a controlled quantity of Fe³⁺ integrated into the structure allowing pore engineering of MOFs, opens new avenues for designing high-performing MOF catalysts with porous framework for sensing applications.