(771d) Metal-Organic Framework-Containing Membranes for Carbon Dioxide Capture

Metal-organic frameworks (MOFs) are a new class of porous crystalline materials, composed of metal ions or clusters connected by organic linkers through strong chemical bonds. Owing to their large surface areas and tunable functionality, MOFs are of potential utility for gas separations relevant to clean energy technologies, such as carbon dioxide capture and hydrogen purification. So far, the majority of gas separation studies on MOFs have focused on adsorptive separations. However, MOF membranes can also have excellent separation performance due to the selective adsorption/transport of one component in the feed mixture through the pore channels of the material.

In particular, MOFs containing open metal sites are good candidates for the fabrication of CO₂ selective membranes, since those sites are known to selectively adsorb/transport CO₂ molecules over other components. Furthermore, CO₂ molecules adsorbed within MOF pores can inhibit the transport of other components in the feed mixture, such that this type membrane can potentially have high selectivity. In this work, thin films of MOFs were grown on porous alumina support and their CO₂ separation properties were investigated.

Meanwhile, it is often very hard to prepare defect-free thin MOF continuous films with large membrane surface area. One of technologically-viable options to achieve high separation performance is incorporating MOF crystals into a suitable polymer matrix. Such mixed-matrix membranes containing MOF nanocrystals were also fabricated and investigated for CO₂ capture.