(64b) Synthesis of Metal-Organic Framework/Activated Biochar Composites for Carbon Capture

With atmospheric carbon dioxide (CO₂) concentration continuing to rise, novel materials need to be developed for capturing carbon. Metal-organic frameworks (MOFs) are metal-based adsorbents that have high surface areas for adsorbing CO₂ but are structurally susceptible to water vapor. Meanwhile, activated biochars are hydrophobic carbon-based adsorbents that have high surface areas for adsorbing CO₂ but low CO₂ selectivity. Such materials can be combined through composite synthesis to minimize their detrimental properties. In this work, magnesium-metal-organic framework-74 (Mg-MOF-74) crystallites were grown on activated biochar with different dimethylformamide (DMF):ethanol:deionized (DI) water concentration ratios (10:1:1, 15:1:1, 20:1:1) through a solvothermal approach to optimize CO₂ adsorption. X-ray diffraction (XRD) highlighted that the MOF-74 crystal structure was maintained during composite synthesis however the crystallite size decreased with the addition of activated biochar and increasing DMF concentration from 362 to 308-352 Å. Fourier-transform infrared (FTIR) spectroscopy revealed that MOF-74 functionalities were retained through composite synthesis but that significant differences in ligand functionality existed between Mg-MOF-74 and the composites and by DMF concentration. However, through nitrogen (N₂) physisorption, specific surface area decreased during composite synthesis from 1080 to 191-204 m²/g due to blockage of the activated biochar pores by the MOF crystallites. Despite this loss of surface area, CO₂ adsorption capacity increased from 0.76 to 1.04-2.00 mmol/g through composite synthesis with the 15:1:1 composite adsorbing the most CO₂. This finding indicated that open metal sites in Mg-MOF-74 crystallites improved carbon capture onto AB.