Rationally Engineered Heterometallic Metalladithiolene Coordination Nanosheets with Defined Atomic Arrangements

Coordination nanosheets are 2D polymers formed by coordination bonds between metal ions and planar organic molecules. They offer high molecular design freedom and unique electronic and chemical properties, making them suitable for various usage. In the two-phase interfacial reaction of metal ions with benzenehexathiol (BHT), highly conductive coordination nanosheets are generated. For nickel ions, porous NiDT (=Ni₃BHT₂) and nonporous NiBHT (=Ni₃BHT) structures are obtained. However, a rational selective synthesis method for these structures is not well-developed. In this study, selective synthesis of NiDT and NiBHT colloidal solutions is achieved by adjusting the BHT to metal ion ratio in a single phase. These colloidal solutions serve as hydrogen evolution catalysts by coating them on an electrode and NiDT is the better catalyst than NiBHT. CuBHT and ZnBHT colloidal solutions are also successfully prepared. Furthermore, nonporous NiCu₂BHT and a new material, NiZn₂BHT are synthesized by filling the NiDT pores with another metal and BHT. These approaches lead to the production of coordination nanosheet inks and the synthesis of heterometallic coordination nanosheets with controlled molecular structures. The introduction of the second metal significantly changes the electrical conductivity. Furthermore, a method is discovered to convert NiBHT to NiCu₂BHT using a transmetallation reaction.