Pentaethylenehexamine modified microporous MOF-199 for improved carbon dioxide uptake and enhanced carbon dioxide-nitrogen selectivity

Synthesis of a metal-organic-framework (MOF) has been gaining increasing interest due to the interesting characteristics and far-reaching functionalities of the material. In this work, a stable pentaethylenehexamine (PEHA) grafted onto microporous structure of MOF-199 was engineered to enhance the CO2 adsorption under repeated cycles. The composition, morphology and structural analyses of the developed adsorbents were performed. Results from XPS, FT-IR, and EDX analyses confirmed successful grafting of the amine groups (-NH2) into the MOF-199 macro and meso-structures which helped to increase the adsorbent affinity for CO2 considerably. Experimental CO2 and N2 adsorption at 278 K indicated that there was an increased CO2 uptake from 2.12 mmol/g (using pristine MOF-199) to 5.95 mmol/g (using PEHA modified MOF-199) with enhanced CO2/N2 selectivity from 36.4 to 71.4. At 298 K and 100 kPa, the adsorption capacity reduced to 4.25 mmol/g but the selectivity increased exponentially to 391.9. The improved performance was sustained even after five successive adsorption−desorption swings due to its high structural integrity.