MOF Supported Amine Materials for CO2 Capture from Air: An Investigation under Dry and Humid Conditions
Lalit A. Darunte, David S. Sholl, Krista S. Walton, & Christopher W. Jones
School of Chemical & Biomolecular Engineering, Georgia Institute of Technology, 311 Ferst Drive, Atlanta, GA 30332, USA
Supported amine materials belong to popular class of solid adsorbent materials for CO2 capture. While flue gas capture has been one of the most researched areas, air capture also offers an attractive and complementary option. Among commonly considered materials as a support for the amines, metal organic frameworks (MOFs) are promising materials with tunable pore structures and properties. We analyzed MIL-101 supported amine materials for CO2 capture from air. Under constraints of the small pore size and relatively fixed availability of open metal sites to bind amines, we consider low and high molecular weight amine structures and the effects of amine structures on equilibrium CO2 capacities. Under dry conditions and for similar nitrogen loadings, low molecular weight amines showed higher equilibrium capacities while high molecular weight amines showed superior cyclic performance. For practical air capture applications, the cyclic stability of materials and equilibrium capacity under humid conditions are important parameters. We have combined X-ray diffraction, gravimetric uptake measurements, a custom-built volumetric system, electron microscopy and infrared spectroscopy to develop an understanding of the effect of humidity on CO2 capture and on the structure of the material. The kinetics of CO2 capture, which have important implications on the working capacity of the sorbent, are also considered.