Frustrated Lewis-Pairs in porous polymer networks for the metal-free activation of small molecules and heterogeneously catalyzed hydrogenation

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Frustrated Lewis pairs (FLP) are compounds or mixtures of Lewis-acids and Lewis-bases which do not form neutralized adducts due to sterical hindrance. Since their discovery in 2006 they have evolved into an independent field of research within the synthetic organic chemistry and molecular organocatalysis community. Due to their high reactivity FLP can activate small molecules such as hydrogen. Thus, they pose enormous potential for the development of transition metal-free hydrogenation catalysts as well as new catalytic processes. To exploit the potential of the FLP and, on this basis on the long term, to develop new chemical processes, their heterogenization is of great importance. So far not mentioned in the scientific and patent literature, this topic will be addressed within this project by the concept Frustrated Lewis pairs in porous polymers. Porous polymers or organic frameworks are ideally suited for the heterogenization of FLP, since due to the modular concept, at least one FLP partner can be used as a monomer and thus, forms an integral part of the porous network. By different synthetic routes porous polymers with Lewis acidic or basic centers are synthesized. These polymers are then used as solid supports with maximum dispersion of the easily accessible active centers and loaded from solution with selected molecular Lewis partners. With a suitable sterical hindrance and electronic structure of the Lewis centers the FLP are formed within the porous networks. They are characterized with a focus on structural, chemical and thermal properties of the networks before and after loading and the catalytic experiments. The catalytic activity of the heterogenized FLP is investigated in accordance with test reactions in the liquid phase that are known from literature for molecular species. The focus is on the hydrogenation of imines, electron-poor alkenes as well as polycyclic aromatic hydrocarbons. Besides hydrogen activation also the activation of carbon dioxide is investigated which is known for a few molecular FLP. In addition, a proof of concept of the heterogeneously transition metal-free gas phase activation of hydrogen and carbon dioxide is aspired. Overall, the project establishes the foundation and initiates new incentives for the interdisciplinary extension of the research field of FLP that was so far dominated by synthetic organic chemistry. It combines further basic research on the preparation and characterization of new functional materials based on FLP and their structure-activity relationships with the application-related development of new technologies in heterogeneous catalysis.