Membranes, methods of making the membranes, and methods of using the membranes are described herein. The membrane can comprise a support layer; and a selective polymer layer disposed (e.g., coated) on the support layer. The selective polymer layer can comprise a polymer matrix (e.g., a hydrophilic polymer, an amine-containing polymer, or a combination thereof), and a guanidine-based mobile carrier dispersed within the polymer matrix. Optionally, the selective polymer later can further include an amine-based mobile carrier, a CO.sub.2-philic ether, a graphene oxide, carbon nanotubes, or a combination thereof, dispersed within the polymer matrix. The membranes can be used to separate carbon dioxide from other gases, such as hydrogen and/or nitrogen. Also provided are methods of separating gas streams using the membranes described herein.

Provided herein are CO.sub.2-selective membranes that can be used to efficiently separate CO.sub.2 and CO. The membranes can be used to produce high-purity CO.sub.2 and CO gas streams from a feed gas stream comprising a mixture of CO.sub.2 and CO (e.g., an exhaust gas stream from a fuel cell, such as a solid oxide fuel cell). In this way, the membranes can be used with a solid oxide fuel cell system to covert CO.sub.2 to CO.

Provided herein are CO.sub.2-selective membranes that can be used to efficiently separate CO.sub.2 and CO. The membranes can be used to produce high-purity CO.sub.2 and CO gas streams from a feed gas stream comprising a mixture of CO.sub.2 and CO (e.g., an exhaust gas stream from a fuel cell, such as a solid oxide fuel cell). In this way, the membranes can be used with a solid oxide fuel cell system to covert CO.sub.2 to CO.

Membranes, methods of making the membranes, and methods of using the membranes are described herein. The membranes can comprise a support layer, and a selective polymer layer disposed on the support layer. The selective polymer layer can comprise a selective polymer matrix and carbon nanotubes dispersed within the selective polymer matrix. The carbon nanotubes can comprise multi-walled carbon nanotubes wrapped in a hydrophilic polymer, such as polyvinylpyrrolidone or a copolymer thereof, such as poly(1-vinylpyrrolidone-co-vinyl acetate). The membranes can exhibit selective permeability to gases. As such, the membranes can be for the selective removal of carbon dioxide and/or hydrogen sulfide from hydrogen and/or nitrogen.

Membranes, methods of making the membranes, and methods of using the membranes are described herein. The membranes can comprise a support layer, and a selective polymer layer disposed on the support layer. The selective polymer layer can comprise a selective polymer matrix and carbon nanotubes dispersed within the selective polymer matrix. The carbon nanotubes can comprise multi-walled carbon nanotubes wrapped in a hydrophilic polymer, such as polyvinylpyrrolidone or a copolymer thereof, such as poly(1-vinylpyrrolidone-co-vinyl acetate). The membranes can exhibit selective permeability to gases. As such, the membranes can be for the selective removal of carbon dioxide and/or hydrogen sulfide from hydrogen and/or nitrogen.

Disclosed is a method for producing a hollow fiber carbon membrane using a hollow fiber carbon membrane-forming material by means of a dry method or dry-wet method comprising a spinning step, a drying step, an infusibilization step, and a carbonization step as basic steps; wherein in the infusibilization step, heat treatment is performed at least two times at different temperatures, with the second temperature being higher than the first temperature. It is preferable that the second heat treatment is performed directly after the first treatment is performed, without once cooling to room temperature. The obtained hollow fiber carbon membrane has improved permeability, without reducing its separation coefficient.

Disclosed is a method for producing a hollow fiber carbon membrane using a hollow fiber carbon membrane-forming material by means of a dry method or dry-wet method comprising a spinning step, a drying step, an infusibilization step, and a carbonization step as basic steps; wherein in the infusibilization step, heat treatment is performed at least two times at different temperatures, with the second temperature being higher than the first temperature. It is preferable that the second heat treatment is performed directly after the first treatment is performed, without once cooling to room temperature. The obtained hollow fiber carbon membrane has improved permeability, without reducing its separation coefficient.

Provided is an interfacial polymerization process for preparation of a highly permeable thin film composite membrane, which can be used for nanofiltration, forward osmosis, or reverse osmosis, particularly for use with brackish water at low energy conditions. The process includes contacting a porous support membrane with an aqueous phase containing a polyamine and a flux enhancing combination of additives that includes a metal chelate additive containing a bidentate ligand and a metal atom or metal ion and a phosphoramide to form a coated support membrane, and applying an organic phase containing a polyfunctional acid halide to the coated support membrane to interfacially polymerize the polyamine and the polyfunctional acid halide to form a discrimination layer of the thin film composite membrane. Also provided are the membranes prepared by the methods and reverse osmosis modules containing the membranes.

Disclosed is a self-wetting porous membrane comprising an aromatic hydrophobic polymer such as polysulfone and a wetting agent comprising a copolymer of formula A-B or A-B-A, wherein A is a hydrophilic segment comprising a polymerized monomer of the formula (I): CH.sub.2═C(R.sup.1)(R.sup.2), wherein R.sup.1 and R.sup.2 are as described herein, and B is an aromatic hydrophobic polymeric segment, wherein segments B and A are linked through an amidoalkylthio group. Also disclosed is a method of preparing a self-wetting membrane comprising casting a solution containing an aromatic hydrophobic polymer and the wetting agent, followed by subjecting the cast solution to phase inversion. The self-wetting porous membrane finds use in hemodialysis, microfiltration, and ultrafiltration.

Disclosed is a self-wetting porous membrane comprising an aromatic hydrophobic polymer such as polysulfone and a wetting agent comprising a copolymer of formula A-B or A-B-A, wherein A is a hydrophilic segment comprising a polymerized monomer of the formula (I): CH.sub.2═C(R.sup.1)(R.sup.2), wherein R.sup.1 and R.sup.2 are as described herein, and B is an aromatic hydrophobic polymeric segment, wherein segments B and A are linked through an amidoalkylthio group. Also disclosed is a method of preparing a self-wetting membrane comprising casting a solution containing an aromatic hydrophobic polymer and the wetting agent, followed by subjecting the cast solution to phase inversion. The self-wetting porous membrane finds use in hemodialysis, microfiltration, and ultrafiltration.