Aminoguanidine Derived N‐Rich Mesoporous Carbon Nitrides with Tunable Nitrogen Contents for Knoevenagel Condensation

Abstract

AbstractNitrogen‐rich carbon nitrides are desired materials for base‐catalysed transformations; however, their synthesis is challenging due to the volatile nature of N at high temperatures. Herein, we report on the temperature‐controlled synthesis of ordered N‐rich mesoporous carbon nitrides (MCNs) via pyrolysis of aminoguanidine by using SBA‐15 as a hard template. The properties and the nitrogen content of the materials were tuned by varying the carbonization temperature in the range of 350–500 °C. At 350 and 400 °C, higher amounts of N could be retained in the MCN framework with the predominant formation of C3N6 having a six‐membered aromatic ring with diamino‐s‐tetrazine moiety, whereas C3N5 with 1‐amino/imino‐1,2,4‐triazole moieties was produced at 450 and 500 °C. The base catalytic activity of MCNs in Knoevenagel condensation of benzaldehyde with malononitrile revealed that the MCN‐400 exhibited the highest catalytic performance by displaying a 96.4 % product yield with toluene as a solvent. The superior catalytic activity of MCN‐400 is attributed to high N content (62.6 wt%), high surface area (235 m2 g−1), and large pore volume (0.74 cm3 g−1). The optimum temperature for obtaining the highest yield of the products is 80 °C, and the catalyst showed good cycling stability for 5 consecutive cycles.