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

元素有机骨架是一类新兴的纳米多孔无机-有机杂化材料，在非均相催化方面具有很高的应用潜力。特别是锡基材料是重要的，基于众所周知的催化性能的掺锡沸石。近年来，基于生物基平台化合物的lewis -酸活性位点，特别是糖异构化的研究，为多相化学催化开辟了一个新的领域。Sn-有机骨架（Sn- of）表现出嵌入有机基质中的活性Sn位点，其内表面化学性质与沸石有很大不同。初步研究表明，Sn-OF具有较高的糖转化活性。然而，在沸石的情况下，醛糖的外映异构化被优选地催化，而不是醛糖到酮糖的异构化。逆反应的选择性可以用不同的反应机制来解释，这可能是由活性位点的类型和它们的化学环境决定的。这种选择性外聚化使获得大量用于制药和食品工业的稀有醛糖成为可能。在这个项目中，来自达姆施塔特工业大学和亚琛工业大学的两个技术化学小组将进一步研究和开发这种催化系统。在TUDA， Sn-OF的合成将被系统地修改，以调整缺陷形式的活性位点的类型和数量。一个替代的合成路线，以更精确地定义活性位点的新材料将开发和全面表征。为了确定最重要的反应参数和评价技术可行性，在连续运行的固定床反应器中进行了外异构化催化。在更高的温度下，将研究其他生物基价值链的短链副产物的形成。在RWTH，重点是外聚化的机理研究和活性位点的表征，以便系统地推导出进一步开发催化剂的结构-活性关系。最后，采用制备催化的方法，对制备稀有醛糖的异构化工艺进行了优化。总体而言，该项目涉及一种基于新催化剂系统的单糖选择性转化的创新方法。它将新型催化剂材料的基础研究与基于知识的新型多相催化工艺的开发相结合，以便在新的价值链中利用可再生原材料。

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.