PHOTOCATALYSIS · Recyclable Metal-free Photocatalysts for Synthetic Chemistry based on Covalent Organic Frameworks

The discovery of smart and highly efficient catalysts for solar energy conversion and green fuel production is a global scientific challenge due to increasing energy demand and related environmental consequences. Synthetic photocatalysis is highly promising, but employs to date expensive and/or toxic metals, such as Pt, Au, Ru, Cd, Ag, and Ir. This hampers the development of large-scale and introduces environmental issues. The aim of this proposal is to develop stable, recyclable and metal-free heterogeneous photocatalysts for the Diels-Alder (D–A) reaction. D–A reactions are one of the most powerful synthetic protocols for the synthesis of unsaturated six-membered rings, yet to be well established for the industry. Herein, we selected porous organic polymers, namely Covalent Organic Frameworks (COFs) and Covalent Triazine Frameworks (CTFs), because they allow synergistic utilization of their skeleton and pores. Due to their high porosity and uniform pores, they allow for confined space synergies and easy mass transport. The pi-species in these catalysts are highly photo-catalytically active. These metal-free insoluble-polymer-catalysts are expected to show high thermal and chemical stability. Therefore, these catalysts can be easily separated out from the reaction mixture and re-activated for cycle use. Furthermore, we will use these catalysts in a continuous-flow reactor, which could open up a new avenue for catalyst industry.