Template‐Free Synthesis of Three‐Dimensional Nanoporous Bulk Graphitic Carbon Nitride with Remarkably Enhanced Photocatalytic Activity and Good Separation Properties

A facile template-free method is presented for the fabrication of three-dimensional (3D) nanoporous bulk graphitic carbon nitride (g-C3N4) with an interconnected framework. Various techniques, namely, X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, elemental analysis, specific surface area measurements (Brunauer–Emmett–Teller method), UV/Vis diffuse reflectance spectroscopy, time-resolved fluorescence decay spectroscopy, electron paramagnetic resonance spectroscopy, and photoelectrochemical measurements, were adopted to analyze the structures and physicochemical properties of the as-prpared samples. The results show that the nanoporous bulk g-C3N4 with a particle size of ca. 20 μm exhibits a high specific surface area, which is ca. 30.9 times higher than that of the original material. The g-C3N4 with such a structure exhibits an improved adsorption capacity for the target pollutants and is readily separable from the photocatalysis reaction system. It is believed that a two-step protonation process plays a key role in the formation of the structure. Furthermore, this 3D nanoporous bulk g-C3N4 also shows more-efficient photogenerated carrier transfer and separation. As a result, the visible-light photocatalytic activity of g-C3N4 is significantly enhanced, and the degradation rates of methyl orange (MO) and rhodamine B (RhB) dyes over the nanoporous bulk g-C3N4 are ca. 5.0 and 22.3 times higher, respectively, than that over the original material.