Full-solar-spectrum absorption photocatalytic selective oxidation coupling of benzylamine over a nitrogen-rich conjugated covalent organic framework

Two-dimensional conjugated covalent organic framework (COF) materials, such as aza-COF based on 1, 4, 5, 8, 9, 12-hexaazatriphenylene (HAT), are gaining prominence in the field of photocatalytic selective organic transformations. This study focused on the application of aza-COF in the full-solar-spectrum photocatalytic selective oxidation coupling of benzylamine derivatives. The crystalline aza-COF, characterized by a narrow energy band gap (1.09 eV), a broad visible light absorption range (200–1600 nm), and excellent charge separation capability, exhibited significant potential for this transformation. Utilizing oxygen as the oxidizing radical species, the photocatalytic system achieved near-complete conversion (86–99 %) and high selectivity for ten substrates at room temperature, resulting in the formation of imine adducts. The study highlights the exceptional functional group compatibility and tolerance of the COF-based heterogeneous photocatalytic system. Notably, the aza-COF photocatalyst demonstrated excellent recyclability, maintaining its catalytic efficiency over five consecutive cycles. These findings underscore the unique and efficient platform that crystalline aza-COF provides for selective organic transformations via photocatalysis under mild conditions.