Bis(diimino)nickel Coordination Nanosheets Modified with Triptycene Moieties for Facile Exfoliation and Enhanced Hydrogen Evolution Catalytic Activity

High Resolution Image Download MS PowerPoint Slide Two-dimensional, π-conjugated coordination nanosheets (CONASHs) have attracted significant attention because of their potential applications in electronics and electrode materials. However, multilayer stacking induced by π–π interlayer interaction originating from their flat chemical structures shields the metal complex sites and decreases their performance. The triptycene-linker ligands in CONASHs form square-planar complexes perpendicular to the horizontal planes of the nanosheets, and the C–H bonds in the ligand are directed out of the plane. These features prevent π–π interlayer interactions and expose the axial positions of the metal complexes to pores. In this study, 2,3,6,7,14,15-hexaaminotriptycene (HATT) was used as a ligand to synthesize triptycene-bridged bis(diimino)nickel complex coordination nanosheets (Ni-HATT) in a film using a gas–liquid interfacial synthesis method. Facile exfoliation into a thin film several nanometers thick with lateral dimensions of a few micrometers was achieved by ultrasonication in isopropanol owing to weakened interlayer interactions. Furthermore, Ni-HATT-modified electrodes prepared by an electrochemical oxidation method exhibited greater hydrogen evolution reaction (HER) electrocatalytic performance than electrodes modified with conventional CONASH composed of a flat-conjugated ligand owing to easy access to the active sites realized by the chemical structure design obtained by the introduction of the HATT ligand.