A dual-carrier cellulose nanofibril hydrogel with spatially decoupled α-FeOOH and chitosan-derived carbon dot domains for synergistic Cr(VI) adsorption and photocatalytic reduction

Polysaccharide hydrogels are promising for coupled Cr(VI) adsorption and photocatalytic reduction, but conventional co-loaded designs provide limited control over functional-domain organization and catalyst–carrier contact. Here, we constructed a dual-carrier polysaccharide hydrogel (SH-3) in which two TEMPO-oxidized cellulose nanofibril (TOCNF) populations independently host the photocatalyst and electron-mediator domains. α-FeOOH was grown in situ on one TOCNF population through Fe 3+ /carboxylate-guided hydrothermal nucleation, while chitosan-derived carbon dots (CS-CDs) were covalently grafted onto a second population by amide coupling. The two functionalized carriers were co-incorporated into a three-dimensional porous network, placing the two functional domains on distinct TOCNF populations while enabling their functional coupling. SH-3 achieved a Langmuir Q max of 176.1 mg g −1 for total-Cr uptake from Cr(VI)-containing solution and an apparent Cr(VI) depletion rate constant of 0.1341 min −1 , outperforming the physically co-mixed control and literature-derived benchmark. Spectroscopic and electrochemical analyses indicated improved charge separation, electron/•O 2 − -mediated Cr(VI) reduction, and partial solid-phase retention of generated Cr(III). These results identify carrier-level organization of functionalized TOCNF populations as a design variable for coupling adsorption and photocatalysis within a polysaccharide hydrogel. Download: Download high-res image (492KB) Download: Download full-size image