Enhanced photocatalytic oxidation activity of supramolecular self-assembled spherical binuclear Zn2Pc2(EP)4/g-C3N4 via π-π stacking interactions for dye-containing wastewater

Enhanced photocatalytic degradation of dyes in wastewater remains a major focus in environmental research. Herein, a novel spherical binuclear metallophthalocyanine (Zn 2 Pc 2 (EP) 4 ) featuring a planar conjugated structure was self-assembled onto g-C 3 N 4 via π-π stacking interactions. This self-assembly, achieved through a facile “in situ” hydrothermal method, resulted in the construction of a g-C 3 N 4 /Zn 2 Pc 2 (EP) 4 biomimetic photocatalyst. A strong π-π stacking interaction between Zn 2 Pc 2 (EP) 4 and g-C 3 N 4 is evidenced by the red shift of the Q-band absorption peak and the elevated Zn 2p 3/2 binding energy. Furthermore, the luminescence intensity of g-C 3 N 4 /Zn 2 Pc 2 (EP) 4 decreases to 53% of that of pure g-C 3 N 4 , indicating that the π-π stacking interaction promotes the separation of photogenerated electron–hole pairs. The g-C 3 N 4 /Zn 2 Pc 2 (EP) 4 photocatalysts showed good photocatalytic oxidation activity toward methylene blue. The catalytic efficiency of g-C 3 N 4 /Zn 2 Pc 2 (EP) 4 for methylene blue reaches 85.1% after 3h of treatment at room temperature, which is 1.94 times higher than that of pure g-C 3 N 4 . The measured first-order kinetic rate constant is 0.0086 min −1 , exhibiting a 3.44-fold enhancement relative to that of pure g-C 3 N 4 . Mechanistic investigations indicated that the highly reactive intermediate g-C 3 N 4 (e − )/[Zn 2 Pc 2 (EP) 4 ]⁺– * O 2 significantly promoted the photocatalytic oxidative degradation of methylene blue in wastewater. The self-assembled supramolecular g-C 3 N 4 /Zn 2 Pc 2 (EP) 4 offers great potential for developing high-efficiency and environmentally friendly photocatalysts for dye-containing wastewater.