Fabrication of Nanoporous 3D Carbon Nitride from Poly(ionic liquid)s for Regiospecific Synthesis of Benzimidazole Frameworks

Abstract

The traditional form of carbon nitride materials poses limitations, particularly in catalysis, due to a limited number of active sites and low surface area. In response to these challenges, two porous carbon nitride tubes (CNTs) with diverse properties were designed and fabricated by introducing different poly(ionic liquid)s (PILs) as templates. Imidazolium-based PILs were synthesized with different ion pairs, including halogen (Br) and chiral amino acid (L-phenylalanine). The results indicate that the morphology and properties of CNTs are influenced by the nature of PIL ion pairs. Synthesized CNT, assisted by PIL-Br (designated as CNT1), demonstrated superior characteristics in terms of thermal stability (up to 640 °C), specific surface area (73.5 m2/g), and recoverability (six runs without a significant decrease in reaction yield), which are the key factors of a high-performance catalyst. In the following, CNT architectures were employed as heterogeneous catalysts, and their catalytic efficiencies were compared in the regiospecific synthesis of benzimidazole ring systems. As expected, CNT1 demonstrates superfast synthesis (8−12 min) of various pharmaceutical benzimidazole scaffolds with excellent yields (up to 95%) under ultrasound irradiation. In a groundbreaking achievement, this is the first report that presents the preparation of a superactive catalyst through the integration of two distinct categories of advanced materials, including ionic polymers and graphite carbon nitrides, for regiospecific multicomponent reactions. This study offers a fresh perspective on enhancing the catalytic activity of graphitic carbon nitride by changing ion pairs of PILs for advanced technological applications.