Capture of Carbon Dioxide from Air and Flue Gas in the Alkylamine-Appended Metal–Organic Framework mmen-Mg 2 (dobpdc)

Two new metal-organic frameworks, M(2)(dobpdc) (M = Zn (1), Mg (2); dobpdc(4-) = 4,4'-dioxido-3,3'-biphenyldicarboxylate), adopting an expanded MOF-74 structure type, were synthesized via solvothermal and microwave methods. Coordinatively unsaturated Mg(2+) cations lining the 18.4-Å-diameter channels of 2 were functionalized with N,N'-dimethylethylenediamine (mmen) to afford Mg(2)(dobpdc)(mmen)(1.6)(H(2)O)(0.4) (mmen-Mg(2)(dobpdc)). This compound displays an exceptional capacity for CO(2) adsorption at low pressures, taking up 2.0 mmol/g (8.1 wt %) at 0.39 mbar and 25 °C, conditions relevant to removal of CO(2) from air, and 3.14 mmol/g (12.1 wt %) at 0.15 bar and 40 °C, conditions relevant to CO(2) capture…