An environmentally benign and widely available precursor, guanidinium chloride, has been employed, for the first time, for the synthesis of mesoporous g-C₃N₄ materials via a nanocasting method using 12 nm colloid silica as a hard template. A series of mesoporous g-C₃N₄ (C₃N₄-G-r) samples with bimodal pore systems (1.8 and 13.4 nm), and high surface areas (146–215 m² g⁻¹) along with large pore volumes (0.57–0.84 m³ g⁻¹), depending on the amount of templates, have been successfully prepared. Several techniques including X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, and CHN elemental analysis have confirmed the formation of graphitic structures and extremely high nitrogen content of the synthesized C₃N₄-G-r materials. In Friedel–Crafts acylation reaction between hexanoyl chloride and benzene, C₃N₄-G-r samples, especially C₃N₄-G-1.0 with a large surface area of 215 m² g⁻¹, have demonstrated high catalytic conversions, affording a maximum yield of 86% of n-hexanophenone in 4 h at 80 °C.

Mesoporous carbon nitride grafted n-bromobutane shows high catalytic activity in the solvent-free cycloaddition of CO₂ with propylene oxide to propylene carbonate, affording a maximum yield of 88% with a TOF up to 10.7 h⁻¹.