Imaging Multistep s‑Triazine Oligomerization via Cobalt-Assisted Deamination and Selective C-C Coupling

Area of Science:

• Materials Science
• Surface Chemistry
• Nanotechnology

Background:

• Tailoring monolayer carbon nitrides requires understanding polymerization mechanisms.
• Visualizing early-stage polymerization, including C/N/H activation and intermediate states, is challenging.
• Existing knowledge lacks detailed molecular-level insights into carbon nitride formation.

Purpose of the Study:

• To elucidate the molecular-level mechanisms of melamine polymerization on a Au(111) surface.
• To characterize the evolution of intermediate states during on-surface synthesis.
• To investigate the role of coadsorbed cobalt in influencing reaction pathways and product structures.

Main Methods:

• Utilizing bond-resolved scanning probe microscopy (SPM) for real-space visualization.
• Employing density functional theory (DFT) calculations to complement experimental observations.
• Analyzing multistep reactions of melamine with coadsorbed cobalt on Au(111).

Main Results:

• Observed the condensation of melamine monomers into s-triazine tetramers as an initial step.
• Identified the transformation of tetramers into C-C-linked octamers and longer oligomers.
• Demonstrated that the Au-Co-N motif affects intermediate configurations, influencing C-N cleavage and C-C coupling.

Conclusions:

• Provided detailed mechanistic insights into the on-surface polymerization of melamine.
• Established a link between intermediate state evolution and the formation of predictable monolayer carbon nitride structures.
• Highlighted the crucial role of metal coadsorbates in controlling material properties.