sp2 carbon-conjugated covalent organic frameworks for efficient photocatalytic degradation and visualized pH detection

The design and fabrication of versatile covalent organic frameworks (COFs) with multiple properties for diverse applications is highly desirable. Here, the difunctional COFs material g–C 18 N 3 –COF was prepared and modified to be applied for efficient photocatalytic degradation of Rhodamine B (RhB) and pH detection, respectively. Owing to the triazine unit which was suitable for photocatalyst construction, g–C 18 N 3 –COF was sensitive to visible light and exhibited excellent photocatalysis capability toward RhB. Specially, the photocatalytic degradation of RhB with a high concentration of 300 ppm using g–C 18 N 3 –COF reached equilibrium within 6 h. Moreover, g–C 18 N 3 –COF was further grown in-situ onto the filter paper to generate a novel composite material g–C 18 N 3 –COF@Paper with bright yellow fluorescence. g–C 18 N 3 –COF@Paper could visualize the pH detection by remarkable changes in its fluorescent intensity and color in the range of pH value from 1 to 5, on account of the protonation of the nitrogen atoms from the triazine ring in g–C 18 N 3 –COF. The triazine-based sp 2 carbon-conjugated g–C 18 N 3 –COF, respectively, used as photocatalyst and sensor in this work offers a new strategy to construct the versatile COFs material, facilitating the application of functional COFs in the environmental protection field.