Realizing Co-Based Coordination Architectures Templated by Polyoxotungstate toward Electrocatalytic Water Splitting...

Two new polyoxotungstate (POT)-templated metal-organic complexes (MOCs) with various architectures, namely, {[Co4(3-dpap)4][W10O32](OH)4}·12H2O (1) and {[Co2(3-Hdpap)2(H2O)4][TeW6O24]}·3H2O (2), were synthesized with an N3,N5-bis(pyridin-3-ylmethyl)-4H-pyrazole-3,5-dicarboxamide (3-dpap) ligand via solvothermal methods. Complex 1 is a two-dimensional (2D) layer constructed from 2D [Co4(3-dpap)4]8+ architectures and free [W10O32]4- anions. Conversely, a 1D supramolecular chain is generated for complex 2 via the hydrogen bond interaction, where the butterfly-like metal-organic units exist in this architecture. The templating effect from POTs played a crucial role in leading to the different architectures and spatial distribution of metal-organic units, as well as their electrocatalysis activity. The electrocatalytic properties of the carbon cloth electrodes decorated with the title complexes (1-2/CC) were studied, and the hydrogen evolution reaction (HER) was systematically evaluated in both alkaline and simulated seawater media. Notably, 1/CC demonstrated superior activity, requiring an overpotential of only 41.67 mV to achieve a current density of 10 mA cm-2 for HER in alkaline solution. Furthermore, at the current density of 100 mA cm-2, 1/CC also showed enhanced activity for the oxygen evolution reaction overpotential (η) of 0.5498 V. Density Functional Theory (DFT) calculations indicated that the POT species and the 2D [Co4(3-dpap)4]8+ architectures have a pronounced impact on the electrocatalytic performance.