Modification of the Mg/DOBDC MOF with Amines to Enhance CO2 Adsorption from Ultradilute Gases

The MOF Mg/DOBDC has one of the highest known CO2 adsorption capacities at the low to moderate CO2 partial pressures relevant for CO2 capture from flue gas but is difficult to regenerate for use in cyclic operation. In this work, Mg/DOBDC is modified by functionalization of its open metal coordination sites with ethylene diamine (ED) to introduce pendent amines into the MOF micropores. DFT calculations and experimental nitrogen physisorption and thermogravimetric analysis suggest that 1 ED molecule is added to each unit cell, on average. This modification both increases the material's CO2 adsorption capacity at ultradilute CO2 partial pressures and increases the regenerability of the material, allowing for cyclic adsorption-desorption cycles with identical adsorption capacities. This is one of the first MOF materials demonstrated to yield significant adsorption capacities from simulated ambient air (400 ppm CO2), and its capacity is competitive with the best-known adsorbents based on amine-oxide composites.