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Rationally designing distinct acidic and basic sites can greatly enhance performance and deepen our understanding of reaction mechanisms. In our current investigation, we studied the utilization of Brønsted acid sites within layered graphitic carbon nitride (g-C3N4) for the first time to enhance the rate of the Friedländer synthesis. The structural and surface analyses confirm the effective integration of -COOH and -SO3H groups into the g-C3N4 lattice. The surface-functionalized g-C3N4-CO-(CH2)3-SO3H exhibits a remarkable acceleration in quinoline formation, surpassing previously mentioned catalysts, and demonstrating notable recyclability under optimized mild reaction conditions. The heightened reaction rate observed over g-C3N4-CO-(CH2)3-SO3H is attributed to its elevated surface acidity. By probing the Friedländer reaction mechanism through surface characterization, examination of reaction intermediates, and investigation of substrate scope, we elucidate the pivotal role of Brønsted acid sites. This study constitutes a comprehensive exploration of metal-free heterogeneous catalysts for the Friedländer reaction, offering a unique contribution to the field. [ABSTRACT FROM AUTHOR]

Rationally designing distinct acidic and basic sites can greatly enhance performance and deepen our understanding of reaction mechanisms. In our current investigation, we studied the utilization of Brønsted acid sites within layered graphitic carbon nitride (g-C3N4) for the first time to enhance the rate of the Friedländer synthesis. The structural and surface analyses confirm the effective integration of -COOH and -SO3H groups into the g-C3N4 lattice. The surface-functionalized g-C3N4-CO-(CH2)3-SO3H exhibits a remarkable acceleration in quinoline formation, surpassing previously mentioned catalysts, and demonstrating notable recyclability under optimized mild reaction conditions. The heightened reaction rate observed over g-C3N4-CO-(CH2)3-SO3H is attributed to its elevated surface acidity. By probing the Friedländer reaction mechanism through surface characterization, examination of reaction intermediates, and investigation of substrate scope, we elucidate the pivotal role of Brønsted acid sites. This study constitutes a comprehensive exploration of metal-free heterogeneous catalysts for the Friedländer reaction, offering a unique contribution to the field. [ABSTRACT FROM AUTHOR]

We have successfully synthesized quinoline derivatives that exhibit easy scalability and responsiveness to multiple stimuli. These derivatives are capable of forming self-assembled nanoscopic aggregates in an aqueous medium. Consequently, when placed in an aqueous environment, we observe dual fluorescence originating from both twisted intramolecular charge transfer and aggregation-induced emission. The introduction of nerve gas agents, such as diethyl chlorophosphate (DClP) or diethylcyanophosphate (DCNP), to the probe molecules facilitates the charge-transfer process, resulting in a red-shift in absorption maxima. Notably, when operating in fluorescence mode, both of these analytes produce distinct output signals, making them easily distinguishable. DCNP generates a blue fluorescence, while the addition of DClP yields cyan fluorescence. Our mechanistic investigation reveals that the initial step involves phosphorylation of the quinoline nitrogen end. However, in the case of DCNP, the released cyanide ion subsequently attacks the carbonyl carbon centre, forming a cyanohydrin derivative. The response to these target analytes appears to be influenced by the nucleophilicity of the quinoline nitrogen end and the electrophilic nature of the carbonyl unit. [ABSTRACT FROM AUTHOR]