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 degrees C pyrolysis and finally formed regular CaO spheres with an average size of 100 nm after an 800 degrees 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.