Novel construction of Z–scheme g–C3N4/PDI organic photocatalyst for excellent sulfamethoxazole degradation rate in water

To improve the generation of main active substances (·O 2 – and h + ) in sulfamethoxazole (SMX) photocatalytic processes by g–C 3 N 4 , graphitic carbon nitride/perylene diimide (g–C 3 N 4 /PDI, CNPDI) organic photocatalyst with Z–scheme heterojunction was synthesized. Simultaneously, the in–situ self–assembled PDI was realized by introducing short straight–chain alkanes containing terminal carboxylic acid groups at the imide position of PDI molecule and regulating the pH value of the reaction system. g–C 3 N 4 and PDI successfully combined via the formation of –O C–NH– during the preparation process. The π–π interaction between them was conducive to the charge migration at the heterogeneous interface. The addition of PDI in g–C 3 N 4 significantly improved the absorption ability of visible light and facilitated the transportation of photogenerated carriers, leading to enhanced photocatalytic properties. When 2 mg of PDI combined with 500 mg of g–C 3 N 4 , the obtained CNPDI–2 demonstrated the optimal degradation rate for SMX. When reacted for 120 min under visible light, the SMX photodegradation rate by CNPDI–2 was up to 96.3 % because more ·O 2 – and h + generated and participated in the reaction process. The corresponding pseudo–first–order kinetic constant (0.0281 min –1 ) in CNPDI–2 photocatalytic system was 2.4 and 51 times than that in g–C 3 N 4 system (0.0105 min –1 ) and PDI system (0.0005 min –1 ), respectively. Additionally, CNPDI–2 demonstrated the commendable stability, which was suitable for SMX removal in water environment.