Dr. Markus Lackinger, Ludwig-Maximilians-University Munich (LMU)

Project:

The aim of the project is the preparation of covalently interconnected organic frameworks on crystalline surfaces and their characterisation by means of Scanning Tunneling Microscopy under Ultrahigh Vacuum conditions.

Two-dimensional (2D) organic frameworks are nano-porous (pore size ~1..5 nm) thin films on a solid substrate where pores are formed by arrangements of organic molecules. These frameworks represent a periodic arrangement of pores and can be used as a template for the adsorption of nanoscopic objects such as other molecules and metal or semiconductor clusters within the pores.

The stability of such networks is mainly determined by the strength of intermolecular bonds. So far, many hydrogen bonded supramolecular nano-porous systems have been prepared and characterized and a great variety of pore sizes and shapes has been accomplished. By introducing metal-coordination bonds the framework stability could already be greatly enhanced, but the final goal is to introduce covalent links between the molecular building blocks. The main challenge arises from the irreversibility of covalent bonds. Hence, during growth, error corrections are impossible which can result in poorly ordered arrangements.

In this project, we want to investigate different methods for the preparation of well ordered substrate supported 2D COFs. The common strategy is to use monomers with carbon-halogen bonds which serve as predetermined breaking points. The halogen substituents will be split off by means of thermal or photochemical activation, thereby generating radicals which will then form covalently bonded networks through addition reactions.

The goal of the project is to develop a fundamental understanding of the process involved and the influence of the most crucial parameters such as substrate material, molecular structure, substrate temperature, and deposition rate. Experimental techniques involve Organic Molecular Beam Epitaxy (OMBE), Scanning Tunneling Microscopy (STM) and Spectroscopy (STS) and potentially Low Energy Electron Diffraction (LEED).

cf. Chem. Commun., 2009, 4456-4458.

Further information:
http://www.2d-materials.com/