Eco-Friendly Synthesis and Morphology Control of MOF-74 for Exceptional CO₂ Capture Performance with DFT Validation

Metal-Organic Frameworks (MOFs) are increasingly acknowledged for their broad applications in direct carbon dioxide (CO₂) capture from the atmosphere. However, traditional synthesis methods often involve toxic compounds, posing significant environmental concerns. This study introduces a rapid and eco-friendly synthesis method for MOF-74 (G-MOF-74), emphasizing controlled morphology to optimize its structural characteristics. By achieving a tailored morphology, this approach enhances the CO₂ adsorption capacity. The resulting structure, characterized by a high surface area, significantly increases the number of accessible active sites for CO₂ molecules, thereby improving overall gas capture performance. The G-MOF-74 demonstrates a notable adsorption capacity of 5.86 mmol/g for CO₂ and 0.91 mmol/g for nitrogen (N₂) at 1.1 bar, highlighting its excellent potential for bulk gas separation applications. Furthermore, the isosteric heat values were determined to be 20.5 kJ/mol for CO₂ adsorption and 13.2 kJ/mol for N₂ adsorption. In the realm of kinetic modeling, the Weber and Morris model emerged as the most suitable, as evidenced by an R² value of 0.968. The Ideal Adsorbed Solution Theory (IAST) analysis, conducted under flue gas conditions, demonstrated a noteworthy selectivity value of 27.5. To gain a deeper understanding of the adsorption mechanism and optimize the material for CO₂ capture, Density Functional Theory (DFT) calculations and Monte Carlo simulations were employed alongside the experimental evaluation. To assess the cyclic stability of G-MOF-74, a series of 15 adsorption–desorption cycles were executed with 150 °C and 100 °C regeneration temperature, revealing a modest capacity loss of 9.91 % and 7.33 %, respectively. These findings underscore the promising potential of G-MOF-74 as an environmentally friendly adsorbent for gas separation applications.