A Tailored Heptazine-Based Porous Polymeric Network as a Versatile Heterogeneous (Photo)catalyst

A heptazine-based microporous polymeric network, HMP-TAPA was synthesised by direct coupling of trichloroheptazine and tris(4-aminophenyl)amine (TAPA). A high surface area of 424 m² /g was achieved, which is the highest surface area among heptazine-based polymeric networks (HMPs). The tailored electron-donor and -acceptor units in HMP-TAPA give broad visible-light absorption. HMP-TAPA was employed as metal-free photocatalyst for oxidative coupling of amines to imines under visible light irradiation with 98 % selectivity. Furthermore, the surface basicity of HMP-TAPA was used to achieve metal-free heterogeneous base catalysis for Knoevenagel condensation under base-free conditions with >99 % conversion. In addition, HMP-TAPA showed extreme robustness over a wide pH range (1-14). The versatility and flexibility of the current material design is beneficial for understanding its photoactivity and surface basicity so as to design dual active (photo)catalyst materials for specific applications.