Mechanochemical Molecular Motion Using Noncovalent Interactions on Graphene and Its Application to Tailoring the Adsorption

Herein we propose a new way to drive and control directional molecular motion on graphene by modifying the noncovalent interactions (NCIs). We show that molecules noncovalently interacting with graphene selectively diffuse away from the mountain (negative curvature) regions to the valley (positive curvature) regions. This is in contrast to previously reported molecular migration from the valley to the mountain of covalently attached molecules on graphene. To generalize the concept, we investigate a series of NCIs, including pi-pi, C-H--pi, lone pair-pi, halogen-pi, cation-pi, and anion-pi, and find the same robust trend. We further demonstrate that such directional motion of noncovalently bonded molecules can be exploited to create binding sites with tunable chemisorption energy on curved graphene. As a proof-of-concept demonstration, we consider the motion of strong electron acceptor tetracyanoquinodimethane (TCNQ) and show that a noticeable change in chemisorption energy can be attained for a set of adsorbates as a consequence of NCI-driven molecular migration of TCNQ. Thus, we propose that NCI-driven molecular migration can provide an additional controllable dimension to overcome the fundamental limitations of heterogeneous catalysis using 2D materials.