Improved supercapacitors and water splitting performances of Anderson {MnMo6} by assembling with Zn-MOF as the host-guest structure

Improving performance by combining polyoxometalates (POM) clusters with metal-organic frameworks (MOFs) containing different transition metals presents a challenge. Here, a solvothermal method was first used to synthesized a POM-based metal-organic frameworks (POMOFs) Zn[N(C4H9)4][MnMo6O18{(OCH2)3CNH2}2]@Zn3(C9H3O6)2·6C3H7NO (HRBNU-5, which Zn[N(C4H9)4][MnMo6O18{(OCH2)3CNH2}2]·3C3H7NO ({Zn[MnMo6]}), Zn3(C9H3O6)2·3C3H7NO (Zn-BTC)) . Structural characterization revealed that the compound is host-guest structure with Zn-BTC encapsulation {Zn[MnMo6]}. In the three-electrode system, its specific capacitance is 851.3 F g-1 at a current density of 1 A g-1, and it remains highly stable (97.2%) after 5000 cycles. In the symmetrical supercapacitor (SSC) system, HRBNU-5 still performs well with energy density and power density of 11.02 Wh kg-1 and 605.7 W kg-1 at 1 A g-1, respectively. Besides, it shows good catalytic performance in 1 M KOH, with overpotentials and Tafel slopes for hydrogen and oxygen evolution reactions of 177 mV (η10 HER), 126.9 mV dec-1 and 370 mV (η50 OER), 36.3 mV dec-1, respectively, outperforming its precursors and most reported literature. The good activity is ascribed to host-guest structure, high conductivity of HRBNU-5 for electron-transfer, and porous structure that facilitates mass transport. This provides new inspiration for the design of Anderson-type POMOFs electrode materials with multiple active sites and a clear structure.