One-pot synthesis of g-C3N4-doped amine-rich porous organic polymer for chlorophenol removal

Abstract

A novel graphitic carbon nitride (g-C₃N₄)/amine-rich porous organic polymer (RAPOP) was synthesized via one-pot polymerization using various molar ratios of melamine (MA)/terephthalaldehyde (TA)/g-C₃N₄ of 4/4/1, 4/4/2 and 4/4/4. The g-C₃N₄ was used as a supporting scaffold, and its stratified structure provided a skeleton. Polymerization between MA and TA mostly occurred on the surface of g-C₃N₄, which formed porous spatial structures, in particular, that of MA/TA/g-C₃N₄ (4/4/2), of which the surface area and pore volume reached 540.36 m² g⁻¹ and 1.502 cm³ g⁻¹, respectively. Their excellent adsorption performance towards 2,4-dichlorophenol was investigated under different conditions. A solution pH of 7 was favorable for adsorption. The presence of Na⁺ and Cl⁻ ions had no adverse effects on the adsorption process, whereas humic acid (HA) led to a slight decrease in performance. Adsorption equilibrium was reached within 40 seconds, and the maximum adsorbed amounts were 188.70 mg g⁻¹, 217.39 mg g⁻¹, 238.10 mg g⁻¹ and 270.27 mg g⁻¹ for MA/TA (4/4), MA/TA/g-C₃N₄ (4/4/4), MA/TA/g-C₃N₄ (4/4/1) and MA/TA/g-C₃N₄ (4/4/2), respectively, at 298 K. Thermodynamic tests indicated that the adsorption proceeded spontaneously and endothermically. Moreover, the adsorbents maintained their high performance and stability after regeneration via treatment with alkali. This work demonstrates that g-C₃N₄/RAPOP can be practically employed to remove chlorophenols from aqueous solutions.