Carbon Nanotube–Chitosan Composite Beads with Radially Aligned Channels and Nanotube‐Exposed Walls for Bilirubin Adsorption

Porous nanocomposite materials combine the advantages of a polymer matrix in forming a stable framework and the nanofillers that provide high surface area. Here, we use carbon nanotubes (CNTs) as nanofillers to fabricate chitosan beads with controlled porous structure. We synthesized spherical chitosan–CNT composite beads via freeze casting by dropping a mixed solution into liquid nitrogen, and the resulting highly porous composite beads contain radially oriented channels with hybrid chitosan–CNT channel walls. In particular, we observed localized regions of small CNT agglomerates embedded within the chitosan matrix at a lower CNT loading (40 wt%), and predominately exposed CNTs distributed throughout the channel walls at a higher loading (80 wt%). Owing to the hierarchical open‐porous structure and mesopores provided by exposed CNTs, these composite beads showed much higher adsorption capacity (43.6 mg g⁻¹ within 2 h) to bilirubin than CNT‐free chitosan beads. Our nanocomposite beads with tunable pore wall structure have potential applications in environmental and biomedical areas such as efficient adsorption materials.