A newly developed spherical boehmite and melamine composite with a mesoporous structure was successfully fabricated

through a spray drying system utilizing a mixture of boehmite sol and melamine. EDX–SEM, FTIR, and TGA analyses

confi rmed the integration of melamine into the boehmite network within the resulting composite. With an increase in melamine

content, the composites exhibited a gradual reduction in porosity compared to their pristine boehmite counterpart.

However, the CO 2 uptake of the composites continued to demonstrate improvement. The boehmite sample modifi ed with 5

mol% of melamine (IMB#5) demonstrated the highest CO 2 adsorption capacity at 19.2 cm 3 g −1 . This value surpassed the

original boehmite sample by 46.1% under conditions of 25 °C and 1 bar. The enhanced adsorption can be attributed to the

development of adsorptive affi nity facilitated by N-derived functional groups (–NH 2 and –CN) within the melamine structure

and their interaction with CO 2 . As a result, the CO 2 /N 2 separation factor and CO 2 /N 2 adsorptive selectivity using the ideal

adsorbed solution theory (IAST) over the IMB#5 sample were 113.3 and 3182, respectively, approximately 3 times and 9.2

times higher than those for the boehmite sample. Density functional theory (DFT) calculations were conducted to investigate

the interaction of melamine on the boehmite surface, as well as the selective adsorption of CO 2 and N 2 gaseous molecules on

the boehmite/melamine composite. It is shown that the melamine mainly interacts with the boehmite via a strong binding of

the N atom of the triazine ring with the Al atom of the boehmite. The adsorption of CO 2 has lower binding enthalpies and

free energies than that of N 2 . These fi ndings indicate that utilizing continuous spray drying holds promise as an eff ective

pathway for scaling up the production of mesoporous boehmite/melamine composite spheres as CO 2 selective adsorbents.