Hard Carbon–Zeolite composites from textile cotton waste: a sustainable route to porous functional materials

NaX–hard carbon (HC) hybrid materials were synthesized by direct incorporation of biowaste-derived HC, obtained from cotton textile waste, into the zeolitic sol–gel precursor during hydrothermal crystallization. The synthesis conditions were optimized to suppress the formation of competing NaP phases, enabling the crystallization of phase-pure FAU-type NaX even at HC loadings as high as 49 wt%. XRD, 29 Si and 27 Al MAS NMR, and XPS analyses confirmed that the zeolite framework remains structurally preserved after HC incorporation. Textural characterization by N 2 , CO 2 and Ar adsorption revealed the coexistence of zeolitic micropores and carbon-derived ultramicropores, giving rise to hybrid materials with complementary microporosity and tunable structural and textural properties. Despite the high carbon content, the composites retained high surface areas and micropore volumes, suggesting that the hard carbon phase contributes complementary accessible porosity in addition to the intrinsic zeolitic microporosity. Overall, this work demonstrates a simple and sustainable strategy for transforming textile waste into functional zeolite–carbon hybrid materials, providing a promising platform for future studies on adsorption and related porous-material applications.