Exfoliated Graphitic Carbon Nitride Nanosheets/Gold Nanoparticles/Spherical Montmorillonite Ternary Porous Heterostructures for the Degradation of Organic Dyes

Water-soluble organic carcinogenic pollutants have become a serious threat to both health and environment. Here, porous ternary spherical montmorillonite/exfoliated graphitic carbon nitride nanosheets/gold nanoparticles (SMt/g-C3N4/Au NPs) heterostructures were facile and green synthesized through a polydopamine chemistry method. These involved the coating of porous SMt with exfoliated g-C3N4 nanosheets and in situ growth of Au NPs. The prepared heterostructures exhibited a universal catalytic ability toward organic dyes, such as methylene blue (MB), rhodamine 6G, and Congo red, in the presence of sodium borohydride (NaBH4). The catalytic activity would improve under high SMt/g-C3N4/Au NPs concentration, high temperature, and high pH values. For example, the apparent reduction rate constant (kapp) and turnover frequency (TOF) toward MB can reach 5.91 min–1 and 302 h–1, respectively, at 35 °C and pH values of 11. Furthermore, the influences of the pH values on the catalytic performance were investigated, and the reason can be attributed to the strong enhanced adsorption capacity of SMt/g-C3N4/Au NPs heterostructures toward organic dyes under the high pH values for facilitating electron transfer from NaBH4 to organic dyes. Moreover, the SMt/g-C3N4/Au NPs heterostructures were quite stable, being recycled at least 10 times with almost unchanged kapp. The excellent catalytic performance and recyclability recommend our synthesized SMt/g-C3N4/Au NPs heterostructures for a wide range of applications in environment and wastewater treatment.