In-situ co-growth of ZIF-8-derived bio-carbon spheres with meso-macroporous hierarchy for stable and rapid carbon dioxide capture

Efficient carbon dioxide (CO2) capture from post-combustion flue gases is crucial for industrial applications. Adsorbents with high adsorption capacity, exceptional stability, high selectivity, and low cost are essential to meet these requirements. In this study, we present the synthesis of bio‑carbon spheres derived from zeolitic imidazolate framework-8 (ZIF-8) using a macro-fluidic technique. The bio‑carbon spheres integrate ZIF-8 for structural orientation and chitosan for the directional assembly of ZIF-8, thereby addressing the limitations of low strength in chitosan-derived carbon spheres and the challenge of macroscopic shaping of ZIF-8 particles. Additionally, the incorporation of ZIF-8 and the enhancement of the carbon skeleton increased the meso-macroporosity, improving CO2 transport and adsorption performance. The bio‑carbon spheres demonstrated a 46.9% higher CO2 adsorption capacity (101 kPa, 1.40 mmol·g−1) compared to pure chitosan carbon granules (101 kPa, 0.96 mmol·g−1) and a 17.8% faster mass transport rate compared to ZIF-8 carbon particles. Moreover, the bio‑carbon spheres exhibit a low wear rate in a simulated fluidized bed, good thermal stability, and stable cyclic regeneration performance. This study offers a novel strategy for developing industrially applicable adsorbents with hierarchical pore structures to enhance CO2 capture.