Conductive Metal–Organic Frameworks with Extra Metallic Sites as an Efficient Electrocatalyst for the Hydrogen Evolution Reaction

Abstract

The 2D conductive metal–organic frameworks (MOFs) are expected to be an ideal electrocatalyst due to their high utilization of metal atoms. Exploring a new conjugated ligand with extra active metallic center can further boost the structural advantages of conductive MOFs. In this work, hexaiminohexaazatrinaphthalene (HAHATN) is employed as a conjugated ligand to construct bimetallic sited conductive MOFs (M23(M13∙HAHATN)2) with an extra M–N2 moiety. Density functional theory (DFT) calculations demonstrate that the 2D conjugated framework renders M23(M13∙HAHATN)2 a high electric conductivity with narrow bandgap (0.19 eV) for electron transfer and a favorable in‐plane porous structure (2.7 nm) for mass transfer. Moreover, the metal atom at the extra M–N2 moiety has a higher unsaturation degree than that at M–N4 linkage, resulting in a stronger ability to donate electrons for enhancing electroactivity. These characteristics endow the new conductive MOFs with an enhanced electroactivity for hydrogen evolution reaction (HER) electrocatalysis. Among the series of M23(M13∙HAHATN)2 MOF, Ni3(Ni3∙HAHATN)2 nanosheets with the optimal structure exhibit a small overpotential of 115 mV at 10 mA cm−2, low Tafel slope of (45.6 mV dec−1), and promising electrocatalytic stability for HER. This work provides an effective strategy for designing conductive MOFs with a favorable structure for electrocatalysis.

Designing MOF Nanoarchitectures for Electrochemical Water Splitting

“…[10,11] Owing to the intrinsic features of large surface areas, adjustable chemical components, tunable pore structures, and diverse topologies, a large number of MOFs have been employed for electrochemical water splitting. [12][13][14][15][16][17] Moreover, the properties of MOFs can be improved or modified by coupling various functional materials, including polyoxometalates (POMs), metal compounds, carbon nanotubes (CNTs), and other conductive substrates to form guests@MOFs or MOF/substrates. [18][19][20][21][22] The superior electrochemical performance of water splitting can be achieved from the combined advantages of more active sites and enhanced conductivity through functionalization.…”

Exposing unsaturated Cu 1 -O 2 sites in nanoscale Cu-MOF for efficient electrocatalytic hydrogen evolution

“…Conductive metal-organic frameworks (MOFs), with dispersed planar metal nodes and unique two-dimensional -conjugated structures (13)(14)(15), have been intensively reported as potential promising electrocatalysts toward hydrogen evolution (16)(17)(18), oxygen evolution and reduction (19,20), electric energy storage (21,22), and so on. Despite fast charge transfer behaviors, conductive MOF in bulk generally has limited redox capability and moderate HER activity, due to the coordinatively saturated metal nodes and small amount of exposed active sites (23,24).…”

Metal–organic framework based bifunctional oxygen electrocatalysts for rechargeable zinc–air batteries: current progress and prospects

“…The main limitations of pristine MOFs for electrocatalysis are their low conductivities and poor stability. Although highly conductive conjugated systems and twisted quadrilateral congurations have been developed to improve the conductivities of MOFs, which pave new ways for applications of pristine MOFs, [170][171][172][173] they are still in the exploration stage and it is very meaningful and important to construct more conductive and stable MOFs.…”