Immobilizing Molecular Metal Dithiolene–Diamine Complexes on 2D Metal–Organic Frameworks for Electrocatalytic H₂Production

Carbon electrocatalysts consisting of metal complexes such as MN_xor MS_xare promising alternatives to high-cost Pt catalysts for the hydrogen evolution reaction (HER). However, the exact HER active sites remain elusive. Here, molecular metal dithiolene-diamine (MS₂N₂, M=Co and Ni), metal bis(dithiolene) (MS₄), and metal bis(diamine) (MN₄) complexes were selectively incorporated into carbon-rich 2D metal–organic frameworks (2D MOFs) as model carbon electrocatalysts. The 2D MOF single layers, powders, and composites with graphene were thus prepared and showed definite active sites for H₂generation. The electrocatalytic HER activity of the 2D MOF-based catalysts with different metal complexes follow the order of MS₂N₂>MN₄>MS₄. Moreover, the protonation preferentially occurred on the metal atoms, and the concomitant heterolytic elimination of H₂was favored on the M–N units in the MS₂N₂active centers. The results provide an in-depth understanding of the catalytic active sites, thus making way for the future development of metal complexes in carbon-rich electrode materials for energy generation.