Synthesis and Structural Characterisation of Metal-Organic Frameworks Derived from Nigerian Organic Acids for Carbon Dioxide Capture Applications

Metal-organic frameworks are porous crystalline materials with exceptional surface areas that have attracted significant global research interest for carbon dioxide capture, given increasing pressure to develop efficient carbon sequestration materials. This study synthesises novel metal-organic frameworks using organic acid linkers derived from citric acid and succinic acid, which are obtainable from locally available Nigerian agricultural feedstocks, coordinated with zinc, copper, and aluminium metal nodes. Synthesis was conducted by solvothermal methods, and structural characterisation was performed by powder X-ray diffraction, scanning electron microscopy, BET surface area and pore size distribution analysis, thermogravimetric analysis, and FTIR spectroscopy. Carbon dioxide adsorption isotherms were measured at 273 and 298 Kelvin using a volumetric gas adsorption analyser. Selectivity for carbon dioxide over nitrogen and methane was evaluated using ideal adsorption solution theory calculations. The stability of frameworks under humid conditions was assessed by exposing samples to 80 percent relative humidity for seven days. Results show that the zinc-based framework exhibited the highest BET surface area of 1,240 square metres per gram and maximum carbon dioxide uptake of 4.8 millimoles per gram at 273 Kelvin and 1 bar pressure. Adsorption isotherms followed a type I pattern consistent with microporous character. Carbon dioxide-to-nitrogen selectivity ratios were competitive with benchmark materials. Humidity stability varied, with the aluminium framework showing the best moisture resistance. The study establishes a foundation for using Nigerian-sourced organic acid feedstocks in sustainable framework synthesis. Keywords: metal-organic frameworks, carbon dioxide capture, organic acid linkers, porous materials, synthesis