title: Tunable molecular separation by nanoporous membranes.
abstract: Metal-organic frameworks offer tremendous potential for efficient separation of molecular mixtures. Different pore sizes and suitable functionalizations of the framework allow for an adjustment of the static selectivity. Here we report membranes which offer dynamic control of the selectivity by remote signals, thus enabling a continuous adjustment of the permeate flux. This is realized by assembling linkers containing photoresponsive azobenzene-side-groups into monolithic, crystalline membranes of metal-organic frameworks. The azobenzene moieties can be switched from the trans to the cis configuration and vice versa by irradiation with ultraviolet or visible light, resulting in a substantial modification of the membrane permeability and separation factor. The precise control of the cis:trans azobenzene ratio, for example, by controlled irradiation times or by simultaneous irradiation with ultraviolet and visible light, enables the continuous tuning of the separation. For hydrogen:carbon-dioxide, the separation factor of this smart membrane can be steplessly adjusted between 3 and 8.
authors.affiliation: Institute of Functional Interfaces (IFG), Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany.
authors.forename: Zhengbang
authors.identifier: 0000-0002-4811-8943
authors.initials: Z
authors.lastname: Wang
authors.affiliation: Institute for Physical Chemistry and Electrochemistry, Leibniz University Hanover, Callinstraße 3a, 30167 Hannover, Germany.
authors.forename: Alexander
authors.identifier: 0000-0002-5866-1106
authors.initials: A
authors.lastname: Knebel
authors.affiliation: Soft Matter Synthesis Lab, Institute of Biological Interfaces 3 (IBG 3), Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany.
authors.forename: Sylvain
authors.initials: S
authors.lastname: Grosjean
authors.affiliation: Institute of Organic Chemistry (IOC), Karlsruhe Institute of Technology (KIT), Fritz-Haber-Weg 6, 76131 Karlsruhe, Germany.
authors.forename: Danny
authors.initials: D
authors.lastname: Wagner
authors.affiliation: Soft Matter Synthesis Lab, Institute of Biological Interfaces 3 (IBG 3), Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany.|Institute of Organic Chemistry (IOC), Karlsruhe Institute of Technology (KIT), Fritz-Haber-Weg 6, 76131 Karlsruhe, Germany.|Institute of Toxicology and Genetics (ITG), Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, D-76344 Eggenstein-Leopoldshafen, Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Bräse
authors.affiliation: Institute of Functional Interfaces (IFG), Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany.
authors.forename: Christof
authors.initials: C
authors.lastname: Wöll
authors.affiliation: Institute for Physical Chemistry and Electrochemistry, Leibniz University Hanover, Callinstraße 3a, 30167 Hannover, Germany.
authors.forename: Jürgen
authors.initials: J
authors.lastname: Caro
authors.affiliation: Institute of Functional Interfaces (IFG), Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany.
authors.forename: Lars
authors.initials: L
authors.lastname: Heinke