Tailoring the hydration of melamine by on-surface confinement

Melamine is the building block of polymeric carbon nitrides (p-CNH), that are able to catalyze the water-splitting reaction under visible light irradiation. We reveal that, upon water adsorption, two adjacent melamine molecules concurrently work for stabilizing the H-bonded water-catalyst complex. V. Lanzilotto et al. DOI:10.1039/D0NA01034K

With the perspective to shed light on the water-splitting mechanism with p-CNH materials, we have studied the hydration properties of one monolayer (1 ML) of melamine grown on the Cu(111) surface under ultra-high-vacuum conditions. The affinity of the amino nitrogen for the copper surface drives the melamine molecules to chemisorb strongly tilted (~65° off the surface) through two partially de-hydrogenated amino groups (NH-Cu). Upon water adsorption, the free amino N of melamine molecule acts as H-donor towards it (N-H⋯OHH)  cooperatively working with an adjacent molecule that acts as a H-acceptor via the triazine-N (CN⋯HOH).

Our study has shown how hydration properties of carbon nitride-based photocatalysts strongly depend on (i) the sample morphology and (ii) the co-presence of different types of functional groups. Retrieve article Tailoring surface-supported water–melamine complexes by cooperative H-bonding interactions, V. Lanzilotto, C. Grazioli, M. Stredansky, Teng Zhang, L. Schio, A. Goldoni, L. Floreano, A. Motta, A. Cossaro, C. Puglia, Nanoscale Adv. 3, 2359 (2021) DOI:10.1039/D0NA01034K