One-piece soft and bendable porous carbon aerogel for advanced dye wastewater treatment: insights from experiments and DFT calculations

In this study, a bilayer soft and bendable carbon aerogel was fabricated by combining sodium alginate (SA) aerogel with cotton fabric. Using the fabric as a supporting scaffold, a uniform aerogel coating and controlled carbonization were achieved, resulting in a significant increase in accessible adsorption active sites. Compared with pure SA aerogel, which suffers from severe shrinkage during carbonization, the bilayer SA/fabric carbon aerogel exhibited substantially enhanced adsorption capacity. Further investigation into the adsorption mechanism revealed that dye adsorption primarily relies on sodium and oxygen species retained after carbonization of SA, while nitrogen doping plays a key role in tailoring the porosity of the carbon matrix. DFT calculations further confirmed that carboxyl sites on the carbon substrate possess stronger binding energy with dye molecules than nitrogen sites. Electrostatic potential and frontier orbital analyses demonstrated enhanced interfacial charge transfer and orbital coupling at carboxyl edges, clarifying the origin of the superior adsorption performance. The final adsorption performance confirmed the great promise of this bilayer carbon aerogel in the field of dye adsorption.