A Diaminopropane-Appended Metal–Organic Framework Enabling Efficient CO2 Capture from Coal Flue Gas via a Mixed Adsorption Mechanism

A new diamine-functionalized metal–organic framework comprised of 2,2-dimethyl-1,3-diaminopropane (dmpn) appended to the Mg2+ sites lining the channels of Mg2(dobpdc) (dobpdc4– = 4,4′-dioxidobiphenyl-3,3′-dicarboxylate) is characterized for the removal of CO2 from the flue gas emissions of coal-fired power plants. Unique to members of this promising class of adsorbents, dmpn–Mg2(dobpdc) displays facile step-shaped adsorption of CO2 from coal flue gas at 40 °C and near complete CO2 desorption upon heating to 100 °C, enabling a high CO2 working capacity (2.42 mmol/g, 9.1 wt %) with a modest 60 °C temperature swing. Evaluation of the thermodynamic parameters of adsorption for dmpn–Mg2(dobpdc) suggests that the narrow temperature swing of its CO2 adsorption steps is due to the high magnitude of its differential enthalpy of adsorption (Δhads = −73 ± 1 kJ/mol), with a larger than expected entropic penalty for CO2 adsorption (Δsads = −204 ± 4 J/mol·K) positioning the step in the optimal range for carbon capture ...