Light-Switchable Polymers of Intrinsic Microporosity

Abstract

The interest in (micro)porous systems is greater than ever before with microporous polymers finding application in areas such as gas storage/separation and catalysis. In contrast to the vast majority of publications on microporous polymers seeking ever higher values for surface area or uptake capacity for a particular gas, this work presents a means to render a microporous system responsive to electromagnetic stimuli. The incorporation of a diarylethene (DAE) derivative in the backbone of a polymer of intrinsic microporosity (PIM) produces a microporous system that exhibits photochromism as proven by UV−vis absorption and NMR studies. In the resulting DAE-PIM, surface area is not a fixed unalterable property but can be influenced by the external and nondestructive stimulus light in a reversible manner. Furthermore, in combination with Matrimid, free-standing membranes can be produced that display light-switchable diffusivity and permeability for carbon dioxide and oxygen. In this way, material scientists are offered the potential to employ only one system that can assume several states with different properties for each.

Aromatic polymers made by reductive polydehalogenation of oligocyclic monomers as conjugated polymers of intrinsic microporosity (C-PIMs)

“…Linear and soluble polymers of intrinsic microporosity (socalled PIMs) have been known since the pioneering work of Budd, McKeown and co-workers. 25,26 Several folding motifs, including on-chain spirobifluorene 27,28 /spirobiindane, 29 binaphthyl, 30 triptycene 31 or norbornyl bis(benzocyclobutene) 32 units, have been introduced to give a shape-persistent folding of rigid-rod type polycyclic segments of linear polymer chains that pack into bulk materials with a persistent free volume. 33 Also several conjugated polymers (CPs) with bulky main chain substituents, including poly(trimethylsilylacetylene)s 34 or poly(diphenylacetylene)s 35 and CPs containing 1,3-phenylene units [36][37][38][39] show a permanent microporosity with S BET surface areas up to 730 m 2 g −1 (so-called conjugated PIMs-C-PIMs).…”

Bringing Porous Organic and Carbon‐Based Materials toward Thin‐Film Applications

“…E) Schematic description of PAF‐1 grown over a pre‐functionalized gold substrate. Reproduced with permission . Copyright 2016, the Royal Society of Chemistry.…”

“…PIM‐based membranes show interesting properties in transport of ions and separation of gases . Gas separation properties of such membranes can be modulated in situ by introducing light responsive PIMs . However, aging was identified as a particular challenge in PIMs as the membrane performance cannot be sustained in long‐term experiments.…”

Molecularly engineered switchable photo-responsive membrane in gas separation for environmental protection

“…This sparks the interest to further improve the membrane processes to yield higher productivity by introducing reversibly switch functional materials in the membrane for a more convenient and energy-saving process [18][19][20][21]. The aim is to go beyond the host-guest interaction related stimuli, whereby researchers are intent to expand the concept of the responsive framework to the structural transformation controlled by the external stimuli [22,23].…”

“…However, as the subsequent sections of this review will reveal, works on photo-responsive systems for gas separation are limited. Other than the lack of understanding the molecularlevel mechanism of photo-responsivity that causes the changes in photo-chromic units upon exposure to light, researchers have encountered obstacles such as the degradation of the photo-chromic unit [21] and reduction in the system's performance due to the incorporation of photo-chromic unit [35].…”