Fabrication of complex hydrogels based on pullulan, nanocellulose and carbon dots using photo-Fenton process to eliminate doxycycline contamination

Overcoming the inherent activity–stability trade-off in photo-Fenton systems requires advanced material architectures that integrate multifunctional synergies. In this study, we developed a multifunctional hydrogel, termed PCCF, fabricated by confining Fe 3 O 4 @polydopamine (PDA) nanoparticles within a three-dimensional (3D) pullulan–nanocellulose matrix specifically tailored for efficient doxycycline (DOX) elimination. PCCF exhibited a hierarchically engineered structure based on three synergistic strategies: (1) a pullulan (Pu)–cellulose nanofibrils (CNF)@carbon dots (CD) co-network with a hierarchically porous architecture (surface area: 230.6 m 2 /g), enabling ultrahigh adsorption capacity (Q m  = 272.9 mg/g); (2) PDA-mediated nanoparticle immobilization to achieve spatial uniformity and reduce catalyst leaching (< 5 ppb Fe after five cycles); and (3) an optically transparent and mechanically resilient hydrogel framework (94.2 % transmittance at 500 nm, tensile strength: 41.7 kPa, elongation at break: 84.5 %). These integrated features synergistically improved the photo-Fenton degradation rate constant of PCCF by 3.03-fold compared to Fe 3 O 4 nanoparticles, while maintaining 90.4 % catalytic efficiency after five cycles. This work establishes a Pu hydrogel-based structural paradigm that harmonizes catalytic activity with long-term stability, offering a versatile blueprint for high-performance environmental remediation systems.