On-Surface Self-Assembly Kinetic Study of Cu-Hexaazatriphenylene 2D Conjugated Metal-Organic Frameworks on Coinage Metals and MoS Substrates.

Supramolecular coordination self-assembly on solid surfaces provides an effective route to form two-dimensional (2D) metal-organic frameworks (MOFs). In such processes, surface-adsorbate interaction plays a key role in determining the MOFs' structural and chemical properties. Here, we conduct a systematic study of Cu-HAT (HAT = 1,4,5,8,9,12-hexaazatriphenylene) 2D conjugated MOFs (-MOFs) self-assembled on Cu(111), Au(111), Ag(111), and MoS substrates. Using scanning tunneling microscopy and density functional theory calculations, we found that the as-formed CuHAT -MOFs on the four substrates exhibit distinctive structural features including lattice constant and molecular conformation. The structural variations can be attributed to the differentiated substrate effects on the 2D -MOFs, including adsorption energy, lattice commensurability, and surface reactivity. Specifically, the framework grown on MoS is nearly identical to its free-standing counterpart. This suggests that the 2D van der Waals (vdW) materials are good candidate substrates for building intrinsic 2D MOFs, which hold promise for next-generation electronic devices.