CO2 separation and capture is a global topic that is closely related to energy and environment. Separation via membrane techniques is energy-efficient compared to other separation techniques. Among various membranes, porous membranes usually have good performance in gas flux but poor performance in selectivity. The flux of a porous membrane is dependent on the membrane thickness; the selectivity of a porous membrane, which makes use of size exclusion, is largely dependent on the uniformity of the pores in the membrane. Atomic layer deposition (ALD) is well-established for its capability of making ultra-thin films and precise tuning of materials structures in atomic precision. In this proposed work, we will use technologies in two issued patents co-owned by the University of New Mexico and Sandia national Labs to fabricate sub-10nm hybrid or microporous membrane for CO2 capture. By our team, the concept of ultra-thin ALD membrane has been demonstrated to be successfully for a membrane for He separation, where a flux of 5.3 sccm/bar-cm2, and a He/N2 selectivity of 1050 have been achieved (Jiang et al, JACS Com). In Phase I of this project, we will: 1) use plasma-location- defined ALD to fabricate an ultra-thin hybrid layer on a nanoporous support; 2) by choosing the correct plasma parameter, ALD parameter, and hybrid ALD precursors with organic ligands, and by making use of the interactions between organic ligands, we expect to control the way how the layer-by-layer stacking of the hybrid ALD precursor molecules will proceed, thereby control the location of organic ligands and the structure of the ALD thin film; 3) by choosing the right ligand, or by removing the organic ligand to form porosity, angstrom-sized channels for fast and selective CO2 transport can be achieved. In this work, we emphasize the hybrid or microporous feature of the membrane. We expect that this new membrane will have CO2 permeance > 2000 GPU, CO2/N2 selectivity > 50-100 (for flue gas separation), and CO2/CH4 (for CO2 or natural gas purification) selectivity > 100-200, suitable for industrial applications at reduced energy cost, for example, CO2 capture from flue gas, CO2 removal from natural gas, CO2 purification for CO2 from mines, etc.
