CO2 uptake and storage by small organic functional phenothiazine molecule - An experimental study

Globally, CO2 levels are rising and thus, dedicated efforts are driven towards CO2 capture and storage. In this work, we have demonstrated for the first time CO2 adsorption and storage by phenothiazine (Pheno) molecule. The amine functionalities of Pheno are exploited for the chemisorption of CO2. A maximum of 0.4 mmol/g of CO2 is adsorbed which equates to 17.6 mg CO2 captured/g of Pheno molecule. This value may seem less but the small size, simplistic functionalities, and cheap cost make this study relevant for CO2 mitigation. The CO2 stored on the Pheno molecule is chemisorbed to form strong carbamide (amide linkage) and thus, difficult to desorb even at a temperature of 150 degrees C. This shows that CO2 is stored strongly (via chemical bond formation) and safely thus, could reduce the accidents resulting from accidental leakage/desorption of CO2 which could be fatal. Pheno based sorbent shows linear response over various concentrations ranging from atmospheric concentration of CO2, 400 ppm to 15% concentrations of CO2 at ambient conditions. The adsorption efficacy of Pheno exponentially decreases with an increase in temperature above room temperature. However, the adsorption efficiency increases with an increase in relative humidity as non-condensable water molecules further provide an additional site for CO2 dissolution and bicarbonate formation which increases CO2 uptake.