A Transparent, High-Strength, and Recyclable Core–Shell Structured Wood Hydrogel Integrated with Carbon Dots for Photodegradation of Rhodamine B

The opacity, fragility, and environmental unfriendliness of the traditional photocatalytic matrix cannot fully utilize the properties of photocatalysts and efficiently degrade pollutants. In this work, a transparent wood hydrogel with a core–shell structure was developed using transparent wood (TW) impregnated with polyacrylic acid (PAA) as the core layer and Bi-N-carbon dots/BiOBr (Bi-N-CDs/BiOBr) photocatalyst-initiated polymerization of acrylic acid (AA) monomers as the shell layer. In the shell layer, nanoscale CDs with rich hydrophilic groups built a link between BiOBr and PAA and strengthened the adsorption–photocatalysis synergistic removal for RhB. The original wood backbone well conserved during preparation led to an anisotropic structure in the resultant Bi-N-CDs/BiOBr@TW photocatalytic wood hydrogel. Namely, after introducing Bi-N-CDs/BiOBr as the linker and reinforcing agent, the tensile strength was up to 3.2 and 11.03 MPa along the radial (R-) and axial (A-) directions, which was 1.6- and 1.06-fold of R-TW and A-TW, respectively. Hence, Bi-N-CDs/BiOBr@TW with high strength furnishes multiple separations and reutilizations, and the RhB removal rate is approximately 85% after five cycles. The Bi-N-CDs/BiOBr@TW exhibited light transmittance up to 64.6 and 52.3% at 800 nm along the R- and A-directions, respectively. Moreover, the adsorption–photocatalysis synergistic rate of Bi-N-CDs/BiOBr@TW reached 93% in 300 min at pH = 7. This paper offers a strategy for fabricating wood hydrogels with outstanding stretchability, transparency, dye removal efficiency, and recyclability, opening a significant route for alleviating dye pollution.