In Situ Monitoring of Copper Benzenehexathiol Coordination Polymer Formation via High-Resolution Liquid-Cell Transmission Electron Microscopy

Liquid-cell transmission electron microscopy (LC-TEM) represents a promising technique for obtaining detailed knowledge about crystal nucleation and growth. For conjugated coordination polymer (c-CP) crystals, which are constructed by linking conjugated organic ligands with metal nodes, the growth mechanism remains poorly understood, making LC-TEM an ideal method to fill this gap. However, the general low stability of these materials under the electron beam has hindered high-resolution experiments. Here, we overcome this obstacle and demonstrate high-resolution LC-TEM experiments for the growth of a copper-linked benzenehexathiol (BHT) c-CP. Surprisingly, the synthesis led to the formation of Cu4(BHT) instead of the expected Cu3(BHT), which is found in corresponding ex-situ experiments. We attribute the formation of different structures in ex-situ and in situ experiments to radiolysis occurring during the interaction of the electron beam with the solutions inside the liquid cell, as well as the restrictions dictated by the laminar flow in the microfluidic system.