Physical Chemistry with Focus on Spectroscopy

Dynamic processes in porous materials are crucial for their applications, ranging from sensor technology over molecular mixture separation to storage and conversion of energy. Furthermore, such processes are the key to the realization of smart materials which dynamically respond to external stimuli.

Well-defined porous films of metal-organic frameworks (MOFs, Nobel Prize in Chemistry 2025) are particularly fascinating. The interaction with the framework and the diffusion of the guest molecules in the pores as well as confinement effects are among the research interests of the work group.

Diffusion and mass transfer

Loading with guest molecules is the key for most applications of nanoporous materials, such as MOFs. Using a quartz crystal microbalance (QCM), time-resolved infrared (IR) or UV-vis spectroscopy, we investigate the mass transfer of various molecules in the nanoporous framework under different conditions.

 

 

Unique sensors and electronic noses

Due to their unique properties, MOF films are an ideal active material for various sensors, especially gas sensors. We make electronic noses (i.e. arrays of gas sensors) with different functional MOF films and use them to identify/"smell" a wide variety of molecules. With the help of homochiral MOF films in a sensor array, the enantiomers of many different chiral molecules could be detected and differentiated simultaneously for the first time. Based on selected MOF films, it is possible for the first time to determine ternary isomer mixtures (e.g. mixtures of the three xylene isomers). In addition to gravimetric sensors, the MOF films are also used as an active material in other types of sensors, such as photonic sensors or graphene transistor sensors.

Smart Nanoporous Coatings – Photoswitchable MOF films

The remote control of physical and chemical properties plays a key role in for intelligent, functional materials. The great potential of thin MOF films containing photoswitchable moieties is being explored. The photoswitchable moieties, such as azobenzene and spiropyran, can be reversibly switched by light of different wavelengths between different forms. This photoswitching influences the interaction between the host framework and the guest molecules, modifying the physicochemical properties. In this way, we realize membranes with remote-controllable permeation, thin films with photoswitchable ionic or electronic conductivity and photo-programmable sensors.

 

       

Ionic Liquids in Confinement

Room temperature ionic liquids confined in porous materials find application in supercapacitors and batteries, as well as in ion-based signal processing. These materials show unique structural and dynamic properties, which we explore.

Ionic liquids in nano-confinement, i.e. in the pores of a nanoporous material, are used in supercapacitors and batteries as well as in ion-based signal processing. The detailed study of the ion dynamics reveals unique and unexpected structural and dynamic properties. For that, the MOF films are a unique model system.

Electric and Semiconductor Properties of MOF films

By incorporating functional organic semiconducting groups in the crystalline lattice, MOFs may have highly interesting semi-conductor properties. This enables photoconduction in MOF thin films (e.g. for light detectors) and p-n junction (like diodes) with a crystalline interface.