Azo-functionalized chitosan porous films: A sustainable approach for enhanced CO2 capture and selectivity

The need for efficient and sustainable CO 2 capture technologies has driven extensive research into different porous materials as adsorbents. However, many of the best-performing materials are derived from petroleum-based precursors, creating a fundamental contradiction in terms of environmental sustainability. Herein, we present a biopolymer-based approach for CO 2 capture by chemically modifying porous chitosan films with azo functionalities. The functionalization, achieved via imine linkages, was confirmed through FTIR, NMR, and UV–Vis, while SEM and TEM verified the preservation of the films’ porous architecture. Thermal stability assessments demonstrated that the azo-modified films retained excellent resistance to degradation, with an onset degradation temperature (T i ) of 279 °C. The introduction of azo groups resulted in a significant enhancement of both CO 2 capture capacity, achieving values of 1.51 mmol g⁻¹ at 273 K and 0.65 mmol g⁻¹ at 298 K, corresponding to an approximate tenfold enhancement compared to pristine chitosan. This modification imparted a favorable N₂-phobic/CO 2 -philic character /N₂ selectivity, as evidenced by a noticeable reduction in adsorption from 0.12 to 0.08 mmol g -1 at 298 K. This work provides a sustainable and scalable platform for developing next-generation CO 2 adsorbents, paving the way for further studies on their adsorption performance and long-term usability under real-world conditions.