Unraveling the conglomeratic nature of methanol clusters adsorbed on graphene surfaces. Insights from molecular dynamics simulations

Abstract

The expression of chirality in adsorption phenomena constitutes an important topic, not only relevant to asymmetric transformations involving solid surfaces, but also to the emergence of homochirality in both terrestrial and extraterrestrial scenarios. Methanol (MeOH) aggregation on graphite/graphene, one of the most idealized adsorbate–adsorbent systems, leads to islands of cyclic clusters of different sizes (Nano Lett., 2016, 16, 3142–3147). Here, we show that this aggregation occurs enantioselectively affording 2D conglomerates depending on the size of clusters, in close analogy to a Pasteurian racemate. Homochiral sequences are held together by hydrogen bonding and other non-covalent interactions, whose absolute configurations can be appropriately specified. A discussion involving the dichotomy between 2D racemates and conglomerates, is offered as well. In addition, the present simulations showcase a broad range of acyclic and cyclic structures, even if some discrete rings are the dominant species, in agreement with previous experimental data and theoretical modeling. Our results indicate that MeOH clusters show binding energies close to the experimental values, remaining intact at temperatures as high as 120 K and up to 150 K.