Metal-free activation of molecular oxygen by covalent triazine frameworks for selective aerobic oxidation.

Abstract

Oxygen activation is a critical step in ubiquitous heterogeneous oxidative processes, most prominently in catalysis, electrolysis, and pharmaceutical applications. We present here our findings on metal-free O₂ activation on covalent triazine frameworks (CTFs) as an important class of N-rich materials. The O₂ activation process was studied for the formation of aldehydes, ketones and imines. A detailed mechanistic study of O₂ activation and the role of nitrogen heteroatoms were comprehensively investigated. The electron paramagnetic resonance (EPR) and control experiments provide strong evidence for the reaction mechanism proving the applicability of the CTFs to activate oxygen into superoxide species. This report highlights the importance of a self-templating procedure to introduce N functionalities for the development of metal-free catalytic materials. The presented findings reveal an important step toward the use of CTFs as inexpensive and high-performance alternatives to metal-based materials not only for catalysis but also for biorelated applications dealing with O₂ activation.