Lewis acidic porous element organic frameworks for the selective catalytic transformation of monosaccharides

• Applicants: Dr. Irina Delidovich, Ph.D.; Professor Dr. Marcus Rose
• Subject Area: Technical Chemistry
• Term: since 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 450360023

Element-organic frameworks are a rather young class of nanoporous inorganic-organic hybrid materials and offer high potential in heterogeneous catalysis. Especially tin-based materials are important based on the well-known catalytic properties of Sn-doped zeolites. Based on their active Lewis-acidic sites especially the conversion of biomass-based platform chemicals has been investigated in recent years and particularly with the isomerization of saccharides, a relatively new area for heterogeneous chemocatalysis has been opened up. The Sn-organic frameworks (Sn-OF) exhibit active Sn sites embedded in an organic matrix with the internal surface chemistry differing significantly from that of the zeolites. In preliminary work it was shown that the Sn-OF show a high activity for the conversion of sugars. However, the epimerization of the aldoses is preferably catalyzed instead of the isomerization of aldoses to ketoses in case of the zeolites. This invers selectivity can be explained by a different reaction mechanism, which is probably defined by the type of active sites and their chemical environment. This selective epimerization enables access to a large number of rare aldoses for use in the pharmaceutical and food industries. In this project, this catalytic system will be further investigated and developed in a complementary collaboration by two groups in technical chemistry from TU Darmstadt and RWTH Aachen University. At TUDA the Sn-OF synthesis will be systematically modified in order to tailor the type and number of active sites in the form of defects. An alternative synthesis route towards new materials with more precisely defined active sites will be developed and comprehensively characterized. The epimerization catalysis is carried out in a continuously operated fixed-bed reactor in order to determine the most important reaction parameters and to evaluate the technical feasibility. At higher temperatures, the formation of shorter-chain by-products for other bio-based value chains will be investigated. At RWTH the focus is on mechanistic studies of the epimerization and the characterization of the active sites in order to systematically derive structure-activity relationships for a further development of the catalysts. Finally, the preparation of rare aldoses is optimized through epimerization using the approach of preparative catalysis. Overall, the project deals with an innovative approach based on a new catalyst system for the selective transformation of monosaccharides. It combines basic research for new catalyst materials with the knowledge-based development of a new heterogeneous catalytic process for the utilization of renewable raw materials in new value chains.

• DFG Programme: Research Grants
• International Connection: Austria