Improved supercapacitors and water splitting performances of Anderson-type manganese(III)-polyoxomolybdate through assembly with Zn-MOF in a host–guest structure

Enhancing performance through the combination of polyoxometalates (POMs) clusters with metal–organic frameworks (MOFs) that contain various transition metals is a challenging task. In this study, we synthesized a polyoxometalate-based metal–organic framework (POMOF) named HRBNU-5 using a solvothermal method. HRBNU-5 is composed of Zn[N(C 4 H 9 ) 4 ][MnMo 6 O 18 {(OCH 2 ) 3 CNH 2 } 2 ]@Zn 3 (C 9 H 3 O 6 ) 2 ·6C 3 H 7 NO, which includes two components: Zn[N(C 4 H 9 ) 4 ][MnMo 6 O 18 {(OCH 2 ) 3 CNH 2 } 2 ]·3C 3 H 7 NO ({Zn[MnMo 6 ]}) and Zn 3 (C 9 H 3 O 6 ) 2 ·3C 3 H 7 NO (Zn-BTC). Structural characterization confirmed the host–guest structure, with Zn-BTC encapsulating {Zn[MnMo 6 ]}. In a three-electrode system, HRBNU-5 exhibited a specific capacitance of 851.3 F g −1 at a current density of 1 A/g and retained high stability (97.2 %) after 5000 cycles. Additionally, HRBNU-5 performed well in aqueous-symmetric/asymmetric supercapacitors (SSC/ASC) in terms of energy density and power density in a double-electrode system. Moreover, it demonstrated excellent catalytic performance in a 1.0 M KOH solution, with low overpotentials and Tafel slopes for hydrogen and oxygen evolution reactions: 177.1 mV (η 10 HER), 126.9 mV dec –1 and 370.3 mV (η 50 OER), 36.3 mV dec –1 , respectively, surpassing its precursors and most reported studies. HRBNU-5′s positive performance is attributed to its host–guest structure, high electron-transfer conductivity, and porous structure that enhances efficient mass transport. This work inspires the design of Anderson-type POMOF electrode materials with multiple active sites and a well-defined structure.