Anisotropic membrane materials for gas separations

Abstract

To date the design of membranes for gas separations has relied on isotropic materials that control the magnitude of mass flux. However, mass flux is a vector quantity and controlling its direction is essential for complete manipulation of diffusion processes. In this article, we show how anisotropic materials enable control of mass flux direction in membranes and allow for novel mechanisms for gas separation. We present a detailed study of the design parameters that control membrane selectivities and permeances and demonstrate that this new class of membranes can provide a new avenue to obtain significant improvements with respect to isotropic materials. We also discuss how the proposed anisotropic membranes can be constructed using isotropic materials. Mass diffusion principles for gas separations in anisotropic membranes are different from those in isotropic materials and this novel strategy for the design of membranes can open new opportunities in membrane separation processes.

Impact of Interfaces on the CO2 Permeability of Photopatterned Two-Stage Thiolene Polymer Films

“…These systems can be engineered using immiscible , and miscible , polymer blends, microphase-separated block copolymers, polymer composites with either permeable or impermeable − fillers, and multilayer films. , Often, the overall gas permeability is controlled by the morphology of these systems, specifically the connectivity and orientation of the most conductive phase. Recently, “meta” membrane systems with precise spatial arrangements of two different polymer components have been conceptualized computationally, inspired by the transformation optics, to guide the transport of different gas molecules to different locations. , Such a system, if realized, can have gas selectivity that is orders of magnitude higher than that of current membranes. For example, a slanted grating patterns consisting of alternating polysulfone and polydimethylsiloxane (PDMS) can have an ideal O 2 /N 2 selectivity of ∼500 and 10 5 when the collection area size is 0.5 and 0.25 μm, correspondingly .…”

“…Recently, “meta” membrane systems with precise spatial arrangements of two different polymer components have been conceptualized computationally, inspired by the transformation optics, to guide the transport of different gas molecules to different locations. , Such a system, if realized, can have gas selectivity that is orders of magnitude higher than that of current membranes. For example, a slanted grating patterns consisting of alternating polysulfone and polydimethylsiloxane (PDMS) can have an ideal O 2 /N 2 selectivity of ∼500 and 10 5 when the collection area size is 0.5 and 0.25 μm, correspondingly . However, the contribution of the polymer–polymer interface is neglected in the studies.…”

The effect of different solvents on the formation of large‐area MOF membranes

“…However, with rapid economic development, carbon emission reduction in petrochemical production presents a short‐term challenge. Therefore, the development of effective CO 2 capture technologies will have a significant impact on the mitigation of the greenhouse effect 3–5 . The majority of gaseous molecules in combustion flue gases exist as mixtures, necessitating additional separation and purification to meet production or exhaust gas emission standards.…”

Magnetically Guided Synthesis of Anisotropic Porous Carbons toward Efficient CO2 Capture and Magnetic Separation of Oil

“…All changes in the relative rates of these two steps have a profound influence on the final porous structure of the RF gel. ,, The porosity is maintained when the organic gels are carbonized into carbon. The introduction of structural anisotropy into porous carbons offers several advantages, − which are (1) hierarchical porosity for efficient mass transport, in particular, for catalytic applications, (2) directionality of the pore scaffold and improved pore connectivity, and (3) increased mechanical resistance. − In the case of aligned pores, for example, an increased flux control or enhanced uptake of liquid or gas in the direction of pores can be achieved . Anisotropic structures and high structural control can be found abundantly in natural systems, such as in mollusk shells, in arthropods such as crabs, or in teeth and bones, to increase the mechanical resistance. − While nature has perfected its control over the structure of complex natural materials, precise control over the architecture of artificial or synthetic materials is still highly limited yet highly desired.…”

“…31−33 In the case of aligned pores, for example, an increased flux control or enhanced uptake of liquid or gas in the direction of pores can be achieved. 34 control can be found abundantly in natural systems, such as in mollusk shells, in arthropods such as crabs, or in teeth and bones, to increase the mechanical resistance. 35−37 While nature has perfected its control over the structure of complex natural materials, precise control over the architecture of artificial or synthetic materials is still highly limited yet highly desired.…”