Chemisorption-Induced Activation of MgCl₂ Film as Realistic Route for Heterogeneous Ziegler–Natta Surfaces under Ultrahigh Vacuum

The preparation of model Ziegler–Natta (ZN) surfaces under ultrahigh vacuum necessitates the activation of MgCl₂ films deposited on a substrate, since these films unexceptionally expose the energetically most stable but catalytically inactive (001) face. Here, we present a method to activate MgCl₂ films with the inactive (001) termination, which was based on the chemisorption of a Lewis base in an analogous way to industrial powder catalyst preparation. We found that a (001)-terminated MgCl₂ film on Cu(110) was activated into a MgCl₂·Lewis base adduct when exposed to a pyridine vapor at a nearly saturated vapor pressure. A dynamic response of the MgCl₂ film to the chemisorption and desorption of a Lewis base was uncovered using low-energy electron diffraction and temperature-programmed desorption.