Development and application of heterogeneous POM-based catalysts
Polyoxometalates (POMs) are well-defined metal-oxyanions linked with oxygen bridges of early transition metals of the main groups 5 or 6 at their highest oxidation state. They can also contain a multitude of hetero anions like phosphate or silicate to improve their chemical and thermal stability. POMs have attracted considerable attention due to their fascinating architectures and attractive physico-chemical properties including strong Brønsted acidity, high proton mobility, fast multi-electron transfer, high solubility in polar solvents and resistance to hydrolytic and oxidative degradations. Many properties of POM materials can be tailored by changing the constituents and counter cations. Especially the enormous multifunctionality of POMs made them in particular attractive for various homogeneous catalysed applications.
However, homogeneous catalysis leads to several drawbacks like difficulties in catalyst separation and recycling as well as purification of the products. Furthermore, the low specific surface area of bulk POM-catalysts limits the field of application. Therefore, the development of heterogeneous POM-based catalysts with higher specific surface area has attracted much attention. Beside a better catalyst separation and catalyst recycling, especially extending the field of applications of POM-based materials to liquid-phase reactions in non-polar solvents and gas-phase reactions is one of the main goals.
There are several possibilities for heterogenization of polyoxometalates:
- Impregnation on a porous support (via physical adsorption)
- Chemical immobilization via grafting on a porous support (covalent bondings using linker molecules)
- Complexation with organic or inorganic cations
- Encapsulation in highly porous frameworks
In the research group “biomass and sustainable production of platform chemicals” we are developing tailored heterogeneous POM-based materials using those heterogenization methods for technical liquid phase and gas-phase applications.
This project is funded by FAU through a Grant of the “Emerging-Talents Initiative (ETI)” (2019/1_Tech_02) for a period of 12 months for the preparation of an ERC Starting Grant proposal.