Developing Bimetallic FeM–Organic Frameworks Based on Ferroalloy Trinuclear Clusters for High-Performance Supercapacitors

Abstract

Incorporating a second metal during the steelmaking process to form iron alloys generally improves the properties of iron. Inspired by iron alloy materials, it is hypothesized that introducing analogous inorganic building units could significantly enhance the porous environment, framework itself charges, and redox performance of metal–organic frameworks (MOFs). Unlike iron alloys, accurately incorporating multiple metals into a single MOF framework poses a considerable challenge. In this study, leveraging the exceptional compatibility of metals within trinuclear clusters, a sequence of alloy-like [M3O(O2C)6] structures (M3 = Fe2Mn, Fe2Co, Fe2Ni) were successfully synthesized, yielding a robust Fe/M-MOF ({Fe2MO(DCPB)2(H2O)2}, (M = Mn, Co, Ni)) material family. Compared to those of the parent Fe-MOF frameworks, the pore attributes of heterometallic Fe/M-MOFs (M = Mn, Co, Ni) are distinctly modulated by the type of alloy-like building structual units. Furthermore, due to the synergistic effects of multi-metallic active sites, Fe2M (with M = Mn, Co, Ni) ternary alloy-like cluster-based materials ({Fe2MO(DCPB)2(H2O)2} (M = Mn, Co, Ni, DCPB = 3,5-di (4′-carboxylphenyl) benozoic acid) exhibit exceptional stability and reversibility in electrochemical reactions, making them candidates for applications in supercapacitors devices. The Fe-MOF, Fe/Mn-MOF, Fe/Co-MOF, and Fe/Ni-MOF demonstrate high specific capacitances of 268, 752, 1145, and 1210 F g−1 at 1 A g−1, respectively. Additionally, an asymmetric solid-state device, Fe/Ni-MOF//AC, achieves a peak energy density of 27.2 Wh·kg−1 at a power density of 750 W·kg−1 and a prolonged cycling life. This straightforward strategy of employing a multi-alloy-like building block offers potential for the precise design and performance enhancement of MOFs and the advancement of sophisticated electrode materials for supercapacitors and energy storage systems.