  Two-dimensional organic porous networks (2DOPNs) have opened new vistas for
tailoring the physicochemical characteristics of metallic surfaces. These
typically chemically bound nanoporous structures act as periodical quantum
wells leading to the 2D confinements of surface electron gases, adatoms and
molecular guests. Here we propose a new type of porous network with weakly
interacting 2,4,6-triphenyl-1,3,5-triazine (TPT) molecules on a Cu(111)
surface, in which a temperature-driven (T-driven) phase transition can
reversibly alter the supramolecular structures from a close-packed (CP-TPT)
phase to a porous-network (PN-TPT) phase. Crucially, only the low-temperature
PN-TPT exhibits subnano-scale cavities that can confine the surface state
electrons and metal adatoms. The confined surface electrons undergo a
significant electronic band renormalization. To activate the spin degree of
freedom, the T-driven PN-TPT structure can additionally trap Co atoms within
the cavities, forming highly ordered quantum dots. Our theoretical simulation
reveals a complex spin carrier transfer from the confined Co cluster to the
neighbouring TPT molecules via the underlying substrate. Our results
demonstrate that weakly interacting 2DOPN offers a unique quantum switch
capable of steering and controlling electrons and spin at surfaces via tailored
quantum confinements.

Materials Science;Mesoscale and Nanoscale Physics