Selectivity of single-molecule dynamics in 2D molecular sieves

The size and shape selectivity of a two dimensional (2D) molecular sieve, consisting of a molecularly engineered host matrix that is self assembled at the liquid solid interface is described. The size and shape dependant dynamics of various guest molecules was analyzed in situ and in real time. The temperature dependence of the diffusion dynamics of the different guests was compared, which permits molecular engineering rules for turning the selectivity of the cavities and channels to be derived. Typical room temperature scanning tunneling microscopy (STM) image was obtained from self-assembled aromatic compound on highly oriented pyrolytic graphite (HOPG) before the addition of guest molecules. The experimental data obeys an Arrhenius dependence for each of the guest molecules, with a pre-exponential factor of the order of 5×10×¹⁴ Hz that could be considered as an intrinsic parameter directly related to the diffusion process in a 2D matrix.