Synergistic potential of 0D/2D amine-functionalized carbon quantum dots/g-C₃N₄ composites in thin film nanocomposite membranes for nanofiltration

Water pollution has emerged as a major global concern with industrial development, emphasizing the need to maintain water quality and reduce pollution. Thin film nanocomposite (TFN) membranes offer energy efficiency, eco-friendliness, and high separation performance for water purification. While 0D/2D nanofillers have been extensively studied in hydrogen evolution and photocatalysis, their potential in membrane applications remained underexplored. Additionally, the use of toxic chemicals poses a barrier to advancing green and sustainable membrane fabrication. In this study, conventional piperazine was partially substituted with greener α-cyclodextrin during interfacial polymerization. Next, an eco-friendly hydrothermal method was employed to synthesize 0D amine-functionalized carbon quantum dots (NCQDs) using sustainable materials such as citric acid and urea. Finally, 0D/2D NCQDs/g-C₃N₄ (CG) composites were incorporated into polyesteramide selectivity layer. The as-synthesized CG-PCT membrane demonstrated a synergistic effect with a 1.6-fold improvement in pure water permeability (PWP) with respect to pristine PCT membranes, alongside high rejection rates for Na₂SO₄, MgSO₄, and MgCl₂, driven by Donnan exclusion and size exclusion mechanisms. This study highlights the potential of 0D/2D nanofillers in TFN membranes for nanofiltration, advancing green and sustainable membrane fabrication methods.