ABSTRACT
The presence of coordinatively unsaturated metal sites is a
particularly interesting feature of many MOFs. These sites can
serve as preferential adsorption sites or catalytically active centers,
thereby potentially enhancing the materials’ performance in gas
storage, gas separation, or catalytic applications. This chapter
reviews the different theoretical approaches to model the adsorp-
tion of small molecules (molecules having no more than three
nonhydrogen atoms) at these sites. After briefly presenting the
most important experimental techniques that are used to investigate
the localized adsorption at the metal sites, the first part of this
review surveys computational studies using electronic structure
methods, especially density functional theory (DFT). Thesemethods
are particularly useful to develop an atomistic understanding of
the interactions governing adsorption, and the most important
(sometimes conflicting) conclusions arising from DFT calculations
are outlined. The second part discusses molecular mechanics
calculations, primarily grand canonical Monte Carlo simulations.
This method is predominantly employed to predict macroscopic
quantities, such as adsorption isotherms. While calculations using
standard parameters may provide qualitative insights, the short-
comings of literature force fields tomodel localizedmetal-adsorbate
interactions are pointed out. In the last part, different approaches to
overcome these deficiencies are discussed. It is shown how recent
improvements that bridge the gap between electronic structure
calculations and molecular mechanics methods enable a more
realistic representation of localized interactions between metal
centers and adsorbed molecules.
