Aminoguanidine Derived N‐Rich Mesoporous Carbon Nitrides with Tunable Nitrogen Contents for Knoevenagel Condensation
Sujanya Maria Ruban, Gurwinder Singh, Kavitha Ramadass, Stalin Joseph, Arsh Ismaili, Chien‐Yu Huang, Xinwei Guan, Prashant Kumar, Yoshihiro Sugi, Ajayan Vinu
Abstract
Abstract Nitrogen‐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 C 3 N 6 having a six‐membered aromatic ring with diamino‐ s ‐tetrazine moiety, whereas C 3 N 5 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 m 2 g −1 ), and large pore volume (0.74 cm 3 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.