<p>A sustainable cellulose-based hydrogel was developed from the invasive aquatic plant <i>Typha angustifolia</i>, utilizing plant-derived cellulose as a robust matrix and plant extract as a reducing agent for CuO nanoparticle synthesis, resulting in a green nanocomposite hydrogel (CuO–CNCH). The nanocomposite was synthesized via an environmentally friendly method, and comprehensive characterization using FTIR, XRD, SEM, EDX, TEM, and XPS confirmed successful crosslinking, uniform embedding of CuO nanoparticles, and homogeneous structural integrity, while XPS analysis verified the + 2 oxidation state of Cu and surface composition of CuO NPs in CuO–CNCH. SEM and TEM analyses revealed a well dispersed nanoparticle distribution within the hydrogel pores. Thermal analysis (TGA/DTG) demonstrated enhanced thermal stability of CuO–CNCH upto 280&#xa0;°C compared to pure cellulose hydrogel, indicating suitability for high temperature applications and potential industrial use. The catalytic performance of CuO–CNCH was evaluated for the degradation of four synthetic dyes Rhodamine B (RhB), Crystal Violet (CV), Chicago Blue (CB), and Methyl Orange (MO) under visible light in the presence of sodium borohydride (NaBH₄). Using catalyst doses of 1.85–2.75 gm and optimized NaBH₄ concentrations, the hydrogel achieved exceptionally high degradation efficiencies of 95.12 ± 1.8% (RhB), 93.60 ± 2.0% (CV), 96.02 ± 1.9% (CB), and 90.80 ± 2.2% (MO). The CuO–CNCH achieved remarkable turnover numbers (TON) up to 30.54 and rate constants (k) ranging from 0.0865 to 0.1808&#xa0;min⁻¹, with the catalyst maintaining its activity over six consecutive cycles, demonstrating excellent stability and recyclability. LC–MS and TOC analyses confirmed complete mineralization and reduced ecotoxicity of dyes, demonstrating that the CuO–CNCH derived from invasive plant biomass is a thermally stable, eco-friendly, and highly effective catalyst for sustainable industrial wastewater remediation.</p> Graphical abstract <p></p>