Abstract:
Rational design and development of acid–base bifunctional heterogeneous catalysts for organic
synthesis is a tough process. A highly efficient, non-toxic, metal-free, low-cost, acid–base bifunctional
sulfonated graphitic carbon nitride (S-g-C3N4) catalyst has been developed. The as-synthesized
S-g-C3N4 catalyst exhibits high catalytic potential towards Knoevenagel condensation and sequential
tandem reactions. The as-synthesized catalyst was developed by sulfonation of graphitic carbon nitride
(g-C3N4). The sulfonation leads to surface functionalization of –SO3H groups onto the catalyst surface.
These –SO3H groups impart acidic nature to the S-g-C3N4 catalyst along with the preexisting basic
nature of the catalyst due to the presence of N-containing moieties. These dual acid–base functionalities
behave as active sites for the sequential catalytic reactions to occur. The S-g-C3N4 catalyst exhibits high
turnover numbers (TON) and high yields in shorter reaction time at optimum conditions of temperature
which demonstrates the high catalytic activity of the S-g-C3N4 nanosheets. The corresponding green
metrics parameters were also calculated, in addition to demonstrating the excellent catalyst recyclability
and reusability. The as-synthesized S-g-C3N4 catalyst provides a metal-free, sustainable and green
approach for utilizing acid–base bifunctional catalysts for sequential organic synthesis.
