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.