Novel sphere-like g-C₃N₄/BiOI composite photocatalysts were prepared by a one-pot EG-assisted solvothermal process in the presence of reactable ionic liquid 1-butyl-3-methylimidazolium iodine ([Bmim]I). The nanostructured heterojunction was formed with g-C₃N₄ covering the surface of BiOI microspheres uniformly. Multiple techniques were applied to investigate the structure, morphology and photocatalytic properties of as-prepared samples. During the reactive process, the ionic liquid acted as solvent, reactant, template and dispersing agent at the same time, leading to g-C₃N₄ being uniformly dispersed on the sphere-like BiOI surface. Three different types of dyes rhodamine B (RhB), methylene blue (MB), methyl orange (MO) were chosen as model pollutants to evaluate the photocatalytic activity of g-C₃N₄/BiOI composite. The as-prepared g-C₃N₄/BiOI composite exhibited much higher photocatalytic activity than the pure BiOI. At the same time, colourless endocrine disrupting chemical bisphenol A (BPA) and phenols 4-chlorophenol (4-CP) were chosen to further evaluate the photocatalytic activity of g-C₃N₄/BiOI composite. The g-C₃N₄/BiOI composite also exhibited much higher photocatalytic activity than the pure BiOI, which showed a broad spectrum of photocatalytic degradation activities. The results indicated that the formed heterojunction of g-C₃N₄ covers the BiOI microspheres contributed to improved electron–hole separation and enhancement in photocatalytic activity. A photocatalytic mechanism of g-C₃N₄/BiOI composites is also proposed.

Graphene-analogue nanostructures defined as a new kind of promising materials with unique electronic, surface and optical properties have received much attention in the fields of catalysis, energy storage, sensing and electronic devices. Due to the distinctive structure characteristics of the graphene-analogue materials, they brought novel and amazing properties. Herein, graphene-analogue carbon nitride (GA-C₃N₄) was synthesized by high-yield, large-scale thermal exfoliation from the graphitic C₃N₄-based intercalation compound. Graphene-analogue carbon nitride exhibited 2D thin-layer structure with 6–9 atomic thickness, a high specific surface area of 30.1 m² g⁻¹, increased photocurrent responses and improved electron transport ability, which could give rise to enhancing the photocatalytic activity and stability. The graphene-analogue carbon nitride had a new features that could make it suitable as a sensor for Cu²⁺ determination. So GA-C₃N₄ is a new but promising candidate for heavy metal ions (Cu²⁺) determination in water environment. The photocatalytic mechanism and photoelectrochemical selective sensing of Cu²⁺ were also discussed.

Due to their unprecedented electronic, surface and optical properties, the atomic-thick graphene-like materials have aroused great interest. Compared with the bulk counterparts, the graphene-like material can not only enhance the internal properties, but also gives rise to new promising properties. Herein, the graphene-like carbon nitride (graphene-like C₃N₄) was synthesized via liquid exfoliation from the bulk graphitic carbon nitride (g-C₃N₄) in 1,3-butanediol (1,3-BUT) for the first time. And the graphene-like C₃N₄ was characterized by X-ray diffraction (XRD), atomic force microscopy (AFM), transmission electron microscopy (TEM), thermogravimetric analysis (TG), and X-ray photoelectron spectroscopy (XPS). The obtained graphene-like C₃N₄ exhibited a two-dimensional thin-layer structure with about 3–6 atoms thickness, a high specific surface area of 32.54 m² g⁻¹, increased photocurrent responses, improved electron transport ability and enhanced photocatalytic activity. The photocatalytic reaction for the organic dye methylene blue (MB) by the graphene-like C₃N₄ followed first-order kinetics. Moreover, the graphene-like C₃N₄ exhibited a higher apparent rate of 0.1262 min⁻¹, which was 3.1 times higher than that of the bulk g-C₃N₄ (0.0409 min⁻¹). The enhanced photocatalytic reaction was due to a high specific surface area and a larger bandgap (by 0.14 eV). The yield of the graphene-like C₃N₄ was up to ∼0.35 mg mL⁻¹. Moreover, the graphene-like C₃N₄ had a new property that it could be used as the sensor for trace amounts of Cu²⁺ determination, so the graphene-like C₃N₄ is a new but promising candidate for heavy metal ions (Cu²⁺) determination in water environment. Photoelectrochemical selective sensing of trace amounts of Cu²⁺ was also discussed.

Novel carbon quantum dot (CQD) modified Bi₂MoO₆ photocatalysts were prepared via a facile hydrothermal process. The CQD modified Bi₂MoO₆ materials were characterized by multiple techniques. The CQDs with the average size of about 7 nm were distributed on the surface of Bi₂MoO₆ nanosheets. The photocatalytic activity of as-prepared CQD modified Bi₂MoO₆ materials was investigated sufficiently by the photodegradation of four different kinds of pollutants, such as ciprofloxacin (CIP), bisphenol A (BPA), tetracycline hydrochloride (TC), and methylene blue (MB). The improved photocatalytic activity was observed for CQD modified Bi₂MoO₆ samples compared with pure Bi₂MoO₆ under visible light irradiation. The CQD modified Bi₂MoO₆ photocatalysts with a CQD content of 2 wt% exhibited the optimum photocatalytic activity, which was found to increase by about 5 times than that of the pure Bi₂MoO₆ for the photodegradation of CIP. This improvement was attributed to the crucial role of CQDs, which acted as a photocenter for absorbing solar light, a charge separation center for suppressing charge recombination, and a catalytic center for pollutant photo-degradation. The main active species were determined to be ˙OH and O^˙− ₂ by the ESR technique and analyzed by calculations as well as XPS valence spectra, and a possible photocatalytic mechanism was also proposed.