Surface Termination of the Metal-Organic Framework HKUST-1: A Theoretical Investigation

The surface morphology and termination
of metal-organic frameworks
(MOF) is of critical importance in many applications, but the surface
properties of these soft materials are conceptually different from
those of other materials like metal or oxide surfaces. Up to now,
experimental investigations are scarce and theoretical simulations
have focused on the bulk properties. The possible surface structure
of the archetypal MOF HKUST-1 is investigated by a first-principles
derived force field in combination with DFT calculations of model
systems. The computed surface energies correctly predict the [111]
surface to be most stable and allow us to obtain an unprecedented
atomistic picture of the surface termination. Entropic factors are
identified to determine the preferred surface termination and to be
the driving force for the MOF growth. On the basis of this, reported
strategies like employing “modulators” during the synthesis
to tailor the crystal morphology are discussed.