Soft and hard templates assisted synthesis mesoporous CuO/g-CN heterostructures for highly enhanced and accelerated Hg(II) photoreduction under visible light.

Herein, triblock copolymer surfactant (F127) and mesoporous silica (MCM-41) as soft and hard templates were employed to synthesize of mesoporous CuO/g-CN heterostructures with large surface areas for Hg(II) photoreduction in existence of formic acid as a holes sacrificial. TEM image for mesoporous CuO/g-CN indicated that CuO NPs are homogeneously distributed with spherical shape in particle size ~5 nm onto the surface of g-CN. Mesoporous 2%CuO/g-CN heterostructure was achieved a high Hg(II) photoreduction rate of 628.74 µmolgh and high photoreduction efficiency of ~100% within 50 min compared with the pure either mesoporous CuO NPs (130.11 µmolgh, 21%) and g-CN (88.54 µmolgh, 14%). The highest Hg(II) photoreduction rate achieved was 628.74 µmolgh, which is 4.83 and 7.1 magnitudes stronger than mesoporous CuO NPs and g-CN. The excellent photocatalytic performance of mesoporous CuO/g-CN heterostructures for Hg(II) photoreduction is referred to highly dispersed mesoporous CuO NPs with small particle size onto g-CN, narrow bandgap, large surface area, a rapid transfer of Hg(II) ions and HCOOH to easily reach the active sites due to the facile penetration through the mesostructure, thus promoting the utilization of porous structure of CuO/g-CN heterostructures for efficient diffusion of Hg(II) ions. The intense interaction between mesoporous CuO NPs and porous g-CN confirms the durability of the CuO/g-CN heterostructures during recyclability for five times.