Preparation of thorny pear residue-based microporous carbon and its adsorption performance for low concentration CO₂

In this study, a high-performance microporous carbon adsorbent for carbon dioxide adsorption was prepared from thorny pear residue, with KOH as the pore-forming agent and urea for modification to enrich nitrogen in the microporous carbon. The effects of activation temperature and urea addition on the pore structure and carbon dioxide adsorption capacity of the microporous carbon were studied. The microporous carbon was characterized using N₂ adsorption/desorption, scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectroscopy (FT-IR). The results showed that the optimum preparation conditions for the microporous carbon were an activation temperature of 700 °C and urea addition of 15wt%; the specific surface area of CAC-15-1.5-700 microporous carbon was 1386m²g^− 1, the micropore volume was 0.584cm³g^− 1, and the maximum carbon dioxide adsorption capacity was 3.80mmolg^− 1, indicating excellent CO₂ adsorption ability. The nitrogen elements on the microporous carbon existed mainly in the form of pyridine N (N-6), pyrrole N (N-5), and quaternary N (N-Q) functional groups, and the high N-5 content was an important factor for carbon dioxide adsorption.