Academic Talk: Covalent Two-dimensional Porous Networks – The Quest for Higher Structural Quality

Presenter: Prof. Dr. Markus LACKINGER

 (Deutsches Museum & Technische Universität München – Physics Department, Germany)

Topic: Covalent Two-dimensional Porous Networks – The Quest for Higher Structural Quality

Time: 10:30 AM, Sep. 6^th (Wednesday)

Location: Conference Room B, BLDG 909-1F

Abstract

Monolayer thick two-dimensional (2D) porous networks are not only ideal model systems for host-guest chemistry, but also offer promising and versatile possibilities for the large-scale functionalization of solid surfaces. High quality porous 2D networks with long-range order and low defect densities are routinely obtained by supramolecular self-assembly. The limited stability of the inherently weak connections between molecules, however, are detrimental for the overall network stability and can become limiting for applications. On the other hand, mechanically and thermally robust networks can be obtained by introducing strong covalent cross-links between the molecules. Yet, unless special precautions are taken, kinetic control of the underlying polymerization reactions in combination with the irreversibility of the newly formed bonds renders error correction during or post growth impossible. The resulting networks necessarily exhibit high defect densities, up to a degree of entire disorder and irregularity. Consequently, improving the structural quality still remains the central issue in the on-surface synthesis of covalent 2D porous networks.

The presentation discusses various approaches to improve the structural quality in surface-supported covalent 2D porous networks. A central concept facilitates error correction by taking advantage of bond reversibility either in the actual polymerization reaction or in the formation of an ordered precursor structure. In the latter case, an isostructural conversion is required to obtain the desired product, i.e. the similarly ordered covalent networks. The discussed examples include self-condensation of boronic acids under reversible conditions, on-surface Ullmann coupling with bond reversibility in a metastable organometallic intermediate, and preliminary results towards a topochemical photopolymerization in a self-assembled monolayer of a three-fold anthracene-triptycene derivative.

Biography

Educational and Professional Experiences：

-studies: physical engineering at the University of Applied Sciences Munich

-PhD in experimental physics from TU Chemnitz (Prof. Michael Hietschold)

-research stay at Columbia University (Prof. George W. Flynn)

-postdoc at the LMU München (Prof. Wolfgang M. Heckl)

-postdocs at the University of California Irvine (Prof. Wilson Ho)

-substitute professorship (LMU München)

-habilitation in material science (LMU München)

-habilitation in experimental physics (TU München)

-adjunct professor (LMU München)

-independent research group leader at the Deutsches Museum in cooperation with TU München

Research Interests：

-surface functionalization with organic molecules

-chemistry on solid surfaces with focus “on-surface polymerization”

-supramolecular self-assembly (kinetics & quantitative thermodynamics)

-scanning probe microscopy (under ambient conditions & in ultra-high vacuum)

-synchrotron based characterization

-x-ray photoelectron spectroscopy (XPS)

-x-ray absorption spectroscopy (NEXAFS)

-Low Energy Electron Diffraction (LEED)

Contact: Prof. Lifeng Chi