The development of a negative electrode for supercapacitors is a critical challenge for the next-generation of energy-storage devices. Herein, we describe two new electrodes formed by the coordination polymers [Ni(itmb) 4 (HPMo 12 O 40 )]•2H 2 O (1) and [Zn(itmb) 3 (H 2 O)(HPMo 12 O 40 )]•4H 2 O (2) (itmb = 1-(imidazo-1-ly)-4-(1,2,4-triazol-1-ylmethyl)benzene), synthesized by a simple hydrothermal method. Compounds 1 and 2 show high capacitances of 477.9 and 890.2 F g -1 , respectively. An asymmetric supercapacitor device assembled using 2 which has novel water-assisted proton channels as negative electrode and active carbon as positive electrode shows ultrahigh energy density and power density of 23.4 W h kg -1 and 3864.4 W kg -1 , respectively. Moreover, the ability to feed a red LED also demonstrates the This article is protected by copyright. All rights reserved. feasibility for practical use. Our results allow a better elucidation of the storage mechanism in polyoxometalate-based coordination polymers and provide a promising direction for exploring novel negative materials for new-generation high-performance supercapacitors.

A new coordination polymer, (Hbpe)(Hbpe){[Cu(pzta)(HO)][PWO]}·5HO (1) (pztaH = 5-(2-pyrazinyl) tetrazolate, bpe = bis(4-pyridyl)ethylene), was synthesized by the hydrothermal method. The structure was determined by single crystal X-ray diffraction analyses and further characterized by the SEM, EDS, BVS, FTIR, and PXRD techniques. In 1, the [PWO] (PW) clusters as bidentate connectors link [Cu(pzta)(HO)] dinuclear copper(ii) complexes to form inorganic-organic chains. These chains and the [Hbpe] counter-cations are fused together via hydrogen bonding to form a 3D supramolecular architecture. While 1 was employed as the electrode in a supercapacitor, the cycling stability (90.7% capacitance retention after 1000 circles) and specific capacitance (168 F g at a current density of 5 A g) of the 1-based electrode are better than those of the parent α-KPWO-based electrode, demonstrating more outstanding electrochemical performances of 1. Besides, the 1-based electrode showed excellent electrocatalytic activities towards the reduction of HO and KIO.