# TEMPO-Oxidized Cellulose Hydrogels Loaded with Copper Nanoparticles as Highly Efficient and Reusable Catalysts for Organic Pollutant Reduction

## TL;DR

Researchers created a reusable hydrogel with copper nanoparticles that efficiently breaks down organic pollutants, offering a low-cost and eco-friendly alternative to expensive catalysts.

## Contribution

A novel hydrogel with copper nanoparticles is developed using a green solvent and TEMPO oxidation for efficient and reusable catalytic pollutant reduction.

## Key findings

- The hydrogel retains its structure and catalytic performance after five cycles of use.
- The hydrogel effectively degrades organic dyes like methyl orange and Congo red.
- The combination of LiBr solvent and TEMPO oxidation enhances nanoparticle loading and catalytic activity.

## Abstract

To successfully prepare cellulose hydrogels through a dissolution–regeneration process, 60 wt% LiBr aqueous solution was used as a green solvent. Carboxyl groups were precisely introduced onto the surface of the cellulose hydrogels through a TEMPO-mediated oxidation reaction, while the three-dimensional network structure and open pore morphology were completely retained. This modification strategy significantly enhanced the loading capacity of the hydrogels with copper nanoparticles (Cu NPs). The experimental results show that the LiBr aqueous solution can efficiently dissolve cellulose, and the TEMPO oxidation introduces carboxyl groups without destroying the stability of the hydrogels. Cu NPs are uniformly dispersed and highly loaded on the surface of the hydrogel because of the anchoring effect of the carboxyl groups. Cu NP-loaded hydrogels exhibit excellent catalytic activity in the NaBH4 reduction of 4-nitrophenol (4-NP). Cu NP-loaded hydrogels maintain their complete structure and good catalytic performance after five consecutive cycles. Moreover, Cu NP-loaded hydrogels demonstrate high efficiency in degrading organic dyes such as methyl orange and Congo red. This study successfully developed efficient, low-cost, and environmentally friendly Cu NP-loaded hydrogel catalysts through the synergistic effect of LiBr green solvent and TEMPO oxidation modification, providing a feasible alternative to noble metal catalysts.