Unveiling the power of defect engineering in MOF-808 to enhance efficient carbon dioxide adsorption and separation by harnessing the potential of DFT analysis

Defect engineering in metal–organic frameworks involves intentionally introducing defects to modify their properties. These defects create new active sites, increase surface area, and enhance overall performance in various applications. If properly designed, these intentional defects can create new active sites and increase the specific surface area and thus the overall performance in various applications. The defect engineering strategy in MOF-808 was evaluated using the second ligand agent in different ratios. The exceptional specific surface area obtained compared to the pristine MOF 808 indicates the realization of the improvement potential of MOFs and the increase of their performance capabilities, especially in adsorbing and sequestering carbon dioxide gas in order to achieve a carbon dioxide-free future. A comprehensive set of characterization tests was conducted on the synthesized compounds in order to determine their physical and chemical properties. The Langmuir isotherm and the Weber and Morris kinetic model were chosen as the most suitable models due to their consistent performance, with R² values surpassing 0.95 across all linker concentrations. In MOF-808 with different linker ratios of 0 %, 5 %, 10 %, 15 %, and 20 %, adsorption capacities of 6.4, 5.9, 6.7, 8.3, and 6.4 mmol/g were determined at 25 °C and 110 kPa, respectively. Notably, MOF-808-15 % exhibited the highest adsorption capacity and a remarkable surface area of 3922 m²/g, indicating a substantial interaction between CO₂ molecules and the available open metal sites. Also, MOF-808 variants showed great moisture stability after being exposed to moist air for 7 days. Furthermore, an assessment of this adsorbent’s performance under flue gas conditions, utilizing the Ideal Adsorption Solution Theory (IAST), underscored its outstanding selectivity, with a significant value of 760, representing a 115-fold increase compared to pristine MOF-808-0 %. Density Functional Theory (DFT) shows better adsorption energy for MOF-808-15 % compared to MOF-808-0 %, implying the effect of defects in CO₂ adsorption. Isosteric heat of adsorption study shows chemisorption phenomenon for all MOF-808 variants. Lastly, an evaluation of the cyclic stability of these MOFs over ten adsorption–desorption cycles showcased their robust and enduring performance, offering promising prospects for industrial applications.