Preparation and properties of carmine radish cellulose/nano-Cu composite porous material and its application for catalytic degradation of organic dyes.

Transforming agricultural waste into functional catalysts addresses both environmental and resource challenges. Specifically, cellulose from discarded carmine radish residue (CRC) was made into a porous support for copper nanoparticles (Cu NPs). Inherent brittleness limits cellulose-based materials' practical use, so hexamethylene diisocyanate (HDI) was introduced as a covalent crosslinker. This approach replaces partial interchain hydrogen bonds with urethane linkages, building a resilient three-dimensional (3D) network in the CRC matrix. FTIR, XRD and 2D-WAXS verified the crosslinking, while low-field NMR showed the chemical network accounted for roughly 66.77% of the system. Mechanical properties were notably enhanced: compressive modulus rose from 30 kPa to 130 kPa, compressive strength stayed at 80 kPa, and compressive strain increased from approximately 62% to 81%. Molecular dynamics simulations confirmed cohesive energy dropped from 101.83 kJ mol-1 to 56.27 kJ mol-1, explaining improved energy dissipation. The toughened CRC scaffold was loaded with ~35 nm Cu NPs to form a CRC/nano-Cu composite. When applied to catalytic dye degradation using NaBH4, the composite achieved near-complete degradation of methylene blue (MB) within 25 min. This performance dramatically outperforms the non-catalytic reaction, which only achieved 29% degradation after 240 min. Furthermore, electrostatic interactions driven by the electron-rich Cu surface conferred strong charge-selectivity for cationic dyes, while the composite retained robust reusability over 5 cycles and high activity under severe ionic interference. This work offers a novel strategy for high-value biomass waste utilization and a mechanism for designing strong bio-based catalytic materials by enhancing energy dissipation through covalent crosslinking.