h-BN Defective Layers as Giant N-Donor Macrocycles for Cu Adatom Trapping from the Underlying Metal Substrate

In the confined zone between a bidimensional material and a metal surface, unexpected effects can take place. In this study, we show that when a nonregular two-dimensional h-BN layer is grown on a Cu(111) surface, metal adatoms spontaneously pop up from the bulk to fill the holes in the structure. We provide ample theoretical support to our findings based on a large set of dispersion-corrected density functional theory calculations and on a detailed analysis of the electronic properties and of the chemical processes at this peculiar interface. The observation can be rationalized in terms of a high affinity of Cu adatoms toward N-donor species. Defective h-BN, exposing N-terminated edges, behaves like a giant multi-N-donor macrocyclic ligand that can encapsulate metal atoms as a consequence of a huge stabilization deriving from the Cu-N bond formation. Our conclusions could apply to other metal surfaces and could even stimulate the idea of trapping different metal atoms from those of the underlying surface (e.g., more precious but more active metals) for catalytic purposes.