Group Additivity for Thermochemical Property Estimation of Lignin Monomers on Pt(111)

Conversion of biomass
has received considerable attention, but
theoretical investigation is challenging due to the large computational
burden. In this contribution, we explore group additivity for computing
the thermochemistry of lignin monomers, and by extension to single-ring
aromatic hydrocarbons, on Pt(111). We find that the previous framework
developed for open-chain molecules and furanics is inadequate for
lignin monomers due to conjugation. Using quantum theory of atoms
in molecules (QTAIM), we find that the type of binding of the adsorbate
atoms with the surface sites, for example, σ, σσ,
or σπ, has an important impact on the conjugation of bonds
in adsorbates. We introduce two new models that account for the type
of binding of the central atom and its nearest neighbors, namely,
a conjugation-based and a site-based scheme, which result in significant
improvement. A total of 591 density functional theory data points
were regressed; cross-validation of the site-based scheme reveals
that mean absolute errors are 2.81 kcal/mol in ΔHf,298, 1.07 cal/(mol K) in ΔS298, and 0.25 cal/(mol K) in Cp,300. The slightly simpler conjugation-based model, which does not resolve
the binding type of all nearest neighbors, also performs well.