Adsorption and ring-opening of lactide on the chiral metal surface Pt(321)S studied by density functional theory

Abstract

We study the adsorption and ring-opening of lactide on the naturally chiral metal surface Pt(321)(S). Lactide is a precursor for polylactic acid ring-opening polymerization, and Pt is a well known catalyst surface. We study, here, the energetics of the ring-opening of lactide on a surface that has a high density of kink atoms. These sites are expected to be present on a realistic Pt surface and show enhanced catalytic activity. The use of a naturally chiral surface also enables us to study potential chiral selectivity effects of the reaction at the same time. Using density functional theory with a functional that includes the van der Waals forces in a first-principles manner, we find modest adsorption energies of around 1.4 eV for the pristine molecule and different ring-opened states. The energy barrier to be overcome in the ring-opening reaction is found to be very small at 0.32 eV and 0.30 eV for LL- and its chiral partner DD-lactide, respectively. These energies are much smaller than the activation energy for a dehydrogenation reaction of 0.78 eV. Our results thus indicate that (a) ring-opening reactions of lactide on Pt(321) can be expected already at very low temperatures, and Pt might be a very effective catalyst for this reaction; (b) the ring-opening reaction rate shows noticeable enantioselectivity.

How Au Outperforms Pt in the Catalytic Reduction of Methane Towards Ethane and Molecular Hydrogen

“…Regarding the comparison with related available experimental information, we have to point out that several works in the literature have inspired the present study. In particular, those on several faces of Pt, Pd and Ni[6,48–50] and clusters of Pt[51]. These experiments agree in general terms with the adsorption energies and barriers that we obtain, but none of them focuses on the final effort to clean the catalyst and start a new cycle again.…”

Room-temperature preparation of a chiral covalent organic framework for the selective adsorption of amino acid enantiomers

“…The larger k 2 values of D-AAs than those of L-AAs indicate different interactions of CTzDa with D-AAs and L-AAs (Table S3, ESI †). 33,34 The adsorption isotherms were evaluated in an initial concentration range of 10-100 mg L À1 at four different temperatures (20-50 C) (Fig. S19, ESI †).…”