A Polymorphic Azobenzene Cage for Energy‐Efficient and Highly Selective p‐Xylene Separation

Abstract

Developing the competence of molecular sorbents for energy‐saving applications, such as C8 separations, requires efficient, stable, scalable, and easily recyclable materials that can readily transition to commercial implementation. Herein, we report an azobenzene‐based cage for the selective separation of p‐xylene isomer across a range of C8 isomers in both vapor and liquid states with selectivity that is higher than the reported all‐organic sorbents. The crystal structure shows non‐porous cages that are separated by p‐xylene molecules through selective CH–π interactions between the azo bonds and the methyl hydrogen atoms of the xylene molecules. This cage is stable in solution and can be regenerated directly under vacuum to be used in multiple cycles. We envisage that this work will promote the investigation of the azo bond as well as guest‐induced crystal‐to‐crystal phase transition in non‐porous organic solids for energy‐intensive separations.

Energy‐Efficient Iodine Uptake by a Molecular Host⋅Guest Crystal

“…To the best of our knowledge, there is no material with this combination of features for porous materials (low‐energy synthesis, moisture insensitivity, no activation, I 2 selectivity (compared to H 2 O), gas adsorption at room temperature and ambient pressure, and SHG). This should foster research efforts toward more sustainable porous materials with reduced carbon footprint [99] . We are now exploring how adaptation of the guest structure impacts the channels shape (porous space), adsorption, and SHG properties.…”

Remotely controllable supramolecular rotor mounted inside a porphyrinic cage

“…38,39 These benefits have led to the development of a large number of photoresponsive molecular machines, self-assemblies, smart materials, drug delivery systems, etc. [40][41][42][43] Usually, a molecular machine consists of a light-responsive component, such as azobenzenes, 44,45 dithienylethenes, 46,47 spiropyranes, [48][49][50] etc., 51 to control its mechanical motion by light in the confinement. However, using a light source to control a molecular machine that is devoid of any photoresponsive component can be very interesting considering its resemblance with the biological machines, e.g., light-driven ion pumps.…”

Fast adsorption and kinetic separation of benzene and cyclohexane/cyclohexene in a microporous metal azolate framework

“…[24][25][26] However, that is extremely challenging for C 6 H 6 / C 6 H 10 /C 6 H 12 with similar sizes. 27 Previous research on MOF materials for separation of C 6 H 6 / C 6 H 12 mainly focused on their thermodynamic sorption behaviours that usually are results of equilibrium sorption aer hours or even days. 28 The study on their kinetic separation is really rare and has yet to be explored for separation of C 6 H 6 / C 6 H 10 /C 6 H 12 .…”