Electroactive Covalent Organic Framework Enabling Photostimulus-Responsive Devices

Abstract

Two-dimensional covalent organic frameworks (2D COFs) feature graphene-type 2D layered sheets but with a tunable structure, electroactivity, and high porosity. If these traits are well-combined, then 2D COFs can be applied in electronics to realize functions with a high degree of complexity. Here, a highly crystalline electroactive COF, BDFamide-Tp, was designed and synthesized. It shows regularly distributed pores with a width of 1.35 nm. Smooth and successive films of such a COF were fabricated and found to be able to increase the conductivity of an organic semiconductor by 103 by interfacial doping. Upon encapsulation of a photoswitchable molecule (spiropyran) into the voids of the COF layer, the resulted devices respond differently to light of different wavelengths. Specifically, the current output ratio after UV vs Vis illumination reaches 100 times, thus effectively creating on and off states. The respective positive and negative feedbacks are memorized by the device and can be reprogrammed by UV/Vis illumination. The reversible photostimulus responsivity and reliable memory of the device are derived from the combination of electroactivity and porosity of the 2D COF. This work shows the capability of 2D COFs in higher-level electronic functions and extends their possible applications in information storage.

Weakly Hydrophilic Imine-Linked Covalent Benzene–Acetylene Frameworks for Photocatalytic H2O2 Production in the Two-Phase System

“…A clearer observation revealed several weak diffraction peaks at 2θ = 6.26, 7.14, 9.30, and 12.04°, which may be ascribed to the corresponding (110), (200), (210), and (220) planes (Figure S3). There was a broad peak at about 24.78°, indicating an interlayer π–π stacking distance of <3.5 Å, typical of a reasonable value for π–π stacking systems . Both COF-TAPT-BPDA and COF-TAPP-BPDA prepared under the same conditions revealed higher crystallinity with similar hexagonal crystalline structures.…”

“…There was a broad peak at about 24.78°, indicating an interlayer π−π stacking distance of <3.5 Å, typical of a reasonable value for π−π stacking systems. 18 Both COF-TAPT-BPDA and COF-TAPP-BPDA prepared under the same conditions revealed higher crystallinity with similar hexagonal crystalline structures. (Figure S9).…”

A self-standing three-dimensional covalent organic framework film

“…Such organic framework material can either extend into two or three dimensions 7 . Extensive exploration of new structures 8 – 10 , topologies 11 – 13 , methods of fabrication 14 – 18 , and applications 19 – 23 of COFs is motivated by a heightened control of atom and pore distributions as well as the properties that derive therefrom. One successful approach to COF crystal synthesis relies on dynamic covalent chemistry 24 – 29 .…”

Flexible Azo-Polyimide-Based Smart Surface with Photoregulatable Surface Micropatterns: Toward Rewritable Information Storage and Wrinkle-Free Device Fabrication

“…Among them, photoresponsive materials have attracted extensive attention because light is a kind of green and environmentally friendly clean energy that can be regulated remotely, rapidly, and accurately. 13−17 Compared to the photoresponsive inorganic transition-metal oxide, photoresponsive organic molecules with reversible conformational changes, such as spiropyran, 18,19 diarylethenes, 20,21 and azobenzene, 22−26 have been widely used in controllable liquid transport, 11 information storage, 27 sensors, 28 anticounterfeiting, 29,30 etc. In particular, the azobenzene and its derivatives demonstrate the obvious variation of the spatial structure and the dipole moments between the stable trans state and the metastable cis state, which endows the azobenzene-containing materials with fascinating properties of a reversible structural change or surface properties upon photoirradiation.…”

“…Today, various materials can respond to external stimuli such as pH, , temperature, humidity, , and magnetic field, , which have been widely used in the fabrication of smart functional devices. Among them, photoresponsive materials have attracted extensive attention because light is a kind of green and environmentally friendly clean energy that can be regulated remotely, rapidly, and accurately. − Compared to the photoresponsive inorganic transition-metal oxide, photoresponsive organic molecules with reversible conformational changes, such as spiropyran, , diarylethenes, , and azobenzene, − have been widely used in controllable liquid transport, information storage, sensors, anticounterfeiting, , etc. In particular, the azobenzene and its derivatives demonstrate the obvious variation of the spatial structure and the dipole moments between the stable trans state and the metastable cis state, which endows the azobenzene-containing materials with fascinating properties of a reversible structural change or surface properties upon photoirradiation. − To date, numerous outstanding studies have been conducted on novel photoresponsive polymers bearing azobenzene groups as side chains for applications in the fabrication of functional devices and smart surfaces. , For example, Tian et al reported a simple strategy for the fabrication of novel photoresponsive semiconductor devices via incorporation of two types of azobenzene groups in the side chain of the conjugated D–A polymer .…”