Research area

 

The research in the Stock group is focused on the synthesis and characterization of inorganic-organic hybrid compounds. It can be divided into two main topics, the synthesis of colloidal core-shell-particles and the synthesis of new crystalline hybrid compounds. An important tool for the latter project is the application of high-throughput methods, which were developed in the past few years. These allow a fast, efficient and systematic investigation of complex parameter systems. The final goal of our studies are the discovery of new highly porous compounds and the investigation of their potential use in gas seperation and storage, as sensor materials, catalysts or molecular sieves or in slow release processes. Here, we are also interested in the switching of properties.

 

High-throughput methology:

 

The developement of high-throughput reactors is almost complete. There are reactors that contain 48 or 24 reaction vessels. They can be used at temperatures up to 200 °C. In addition, we were able to incorporate a temperature gradient reactor for temperatures up to 100 °C that has been successfully used in recent studies. To expand the synthetic possibilities in our group, a microwave high-throughput reactor for 24 samples at time is currently developed in collaboration with Anton-Paar.

 

Exploratory synthesis of inorganic-organic hybrid compounds:

 

A very large part of the research in our group is concerned with the synthesis of compounds under hydrothermal reaction conditions. A large variety of reactions systems such as metal phosphonates, borates, arsenates or molybdates have been investigated (often in collaboration with other groups), but my own interest is more focused on the exploratory investigation of inorganic-organic hybrid compounds. Systems which were systematically studied are based on metal phosphonates, phosphonocarboxylates and carboxylates. Recently, we have also startet to look at new hybrid compounds such as the ones based on metal phosphonosulfonate and metal organogermanates. Especially the studies using dicarboxylic acids have led to highly porous materials, mostly based on the well known MIL-compounds. One main interest is the introduction of functional groups that allow modifying the properties of the pore walls. Here, post-synthetic modification reactions play a major role.

 

Post-synthetic modification:

 

Another focus in recent project lies on the post-synthetic modification of porous compounds (especially MOFs) in order to introduce new functionalities or specific host-guest interactions. Promising parent structures of MILs and MOFs are used, such as MOF-5, MIL-101 or MIL-53. The introduction of simple functional groups can be accomplished by starting from carboxylic acids containing a methyl, amino, hydroxy, bromo, etc... Those can be used for further organic reactions to introduce larger molecules.

 

Synthesis of stimuli responsive core-shell particles:

 

Environmentally responsive polymeric core-shell particles in the nano- to micrometer range have attracted great attention in recent years, due to their practical and potential applications for expample in controlled release systems, encapsulation and heterogeneous catalysis. The diffusion through the polymer shell can be controlled by external stimuli (temperature, pH-value, solvent quality, magnetic and electric field), which directly influences the transport properties of guest molecules in and out of the inner core. Poly-N-isopropylacrylamide (PNIPAm) based polymergels are known to undergo a temperature induced volume phase transition, characterized by a lower critical solution temperature (LCST) of about 32 °C. The combination of this function with the well defined porosity of zeolites, periodic mesoporous silica (PMS) or metal organic frameworks (MOFs) could lead to materials with temperature controlled size selectivities of guests. The aim of our work is the synthesis and characterization of colloidal core-shell particles with a porous core and a temperature-sensitive PNIPAm shell.



These projects are supported by the following programs

 

 

 

DFG STO 643/2: Hochdurchsatz-Methoden zur systematischen Untersuchung neuer anorganisch-organischer Hybridverbindungen auf Basis polyfunktionalisierter Phosphonsäuren

 

DFG SPP 1362: Targeting selective host-guest interactions in functionalized MOFs synthesis NMR-studies and sensor design

 

DFG SPP 1259: Bifunktionale core-shell Partikel mit anorganischem porösem Kern und "intelligenter" Hydrogel-Hülle