Forschung

The introduction of defined nanostructures in materials can improve their properties or even create entirely new properties. In the group we deal with two different types of nanostructured inorganic materials. One focus are mesoporous silicates and metal oxides, which are created by solg-gel and templating strategies. The other are metal nanoparticles made by colloidal synthesis. For both material classes of substances, the nanostructuring greatly increases the surface-to-volume ratio. This makes these materials predestined for all applications in which surface (atoms) play a role, mainly catalysis. In a number of projects, e.g. in the UniSysCat Cluster of Excellence, we are therefore researching nanostructured materials as catalysts, among other things for electrocatalytic water splitting or the conversion of CO₂ into valuable chemicals. 

Covalent Organic Frameworks (COFs) are crystalline porous polymeric materials comprised of light weight organic struts connected by covalent linkages. The reticulation of COFs into the thermodynamically favored crystalline products is generally achieved by exploiting reversible processes called dynamic covalent chemistry. By linking such molecular building blocks via strong covalent bonds to crystalline open scaffold materials, our synthetic toolbox has expanded significantly to create materials with an unprecedented level of control over chemistry, structure and porosity. Today a variety of binding patterns, structures and topologies of COFs are known. The Thomas group develops novel COF materials for a range of applications, from catalysis, photo- and electrocatalysis to energy storage devices.

Microporous Polymer Networks (MPNs) feature pores of diameters below 2 nm and consequently very high surface areas and are exclusively built up from organic matter connected by covalent bonds. The synthetic concepts to prepare microporous polymers are highly diverse and range from metal catalyzed couplings to metal-free condensation reactions. The generation of microporosity and sometimes astonishing high surface areas in such polymers stems from the stable, covalent connection of rigid, contorted molecules, with at least two but most often three and more functional and polymerizable groups. Robustness and the possibility of introducing various functional groups make MPNs highly suitable candidates for a range of applications. Probably most intriguing is the possibility to bridge the gap between homogeneous and heterogeneous catalysis by using molecular catalysts as maintaining building block for the generation of highly microporous networks, without the need for an additional porous support. This concept enables the introduction of the highest amount of catalytic active sites per surface area and mass of material.

The replacement of fossil resources by sustainable and green synthetic fuels and chemicals is inevitable to reduce the emission of CO₂ significantly and thus to combat climate change. Direct photocatalysis is an appealing one-step method to generate hydrogen as storable fuel from water using sunlight as energy source, especially because no complicated setups are required, thus such a process could be easily decentralized and also carried out in industrially less-developed areas. The key compound for photocatalysis is a solid semiconductor, which after light irradiation generates charge carriers, to drive the required reduction/oxidation reactions. The Thomas group develops porous organic photocatalysts, such as COFs and CMPs which can be prepared at ambient conditions, allowing to tailor their structure and optoelectronic properties for the desired reaction. Beside photocatalytic water splitting we are also working on photocatalytic CO₂ reduction, H₂O₂ production and metallaphotocatalysis.