MOF-derived nano CaO for highly efficient CO₂ fast adsorption

Calcium looping is considered to be one of the best approaches for industrial CO₂ high-temperature capture, whereas current CaO-based sorbent suffers poor cyclic performance, especially the relations between precursor structure and CO₂ fast adsorption capacity still need to be further revealed. In this work, three calcium-based metal frameworks (Ca-MOFs) with specific structures were employed as precursors to obtain nano CaO through a two-step thermal transition process. It was found that LAC MOF-derived CaO achieved a fast adsorption capacity of 11.8 mmol g⁻¹ (78 % of total adsorption) after 4 cycles. This was because the fiber bundle-like original LAC MOF structure changed gradually to nanosheets after 600 °C pyrolysis and finally formed regular CaO spheres with an average size of 100 nm after an 800 °C -calcination, thereby preventing further aggregation of CaO particles during the thermal transition process. In addition, the adsorption performance did not rely on pore structure, and thus pore-blocking showed little influence on the performance of CO₂ capture. Hence, high stability can be achieved simply by avoiding particle sintering. The systematic study marks the significance of precise tailoring of nano-CaO for achieving the desired performance of CO₂ fast adsorption.