Redox‐Active Azulene‐based 2D Conjugated Covalent Organic Framework for Organic Memristors

Abstract

As a conjugated and unsymmetric building block composed of an electron-poor seven-membered sp 2 carbon ring and an electron-rich five-membered carbon ring, azulene and its derivatives have been recognized as one of the most promising building blocks for novel electronic devices due to its intrinsic redox activity. By using 1,3,5-tris(4-aminophenyl)-benzene and azulene-1,3-dicarbaldehyde as the starting materials, an azulene(Azu)-based 2D conjugated covalent organic framework, COF-Azu, is prepared through liquid-liquid interface polymerization strategy for the first time. The as-fabricated Al/COF-Azu/indium tin oxide (ITO) memristor shows typical non-volatile resistive switching performance due to the electric filed induced intramolecular charge transfer effect. Associated with the unique memristive performance, a simple convolutional neural network is built for image recognition. After 8 epochs of training, image recognition accuracy of 80 % for a neutral network trained on a larger data set is achieved.Ultrathin and uniform two-dimensional (2D) conjugated covalent organic frameworks (COFs) exhibit great application potential in e.g. optoelectronics, catalysis, drug delivery, sensors, energy storage, membrane separation and photonics due to their favorable intrinsic carrier mobility, tunable layered porous structures and functions. [1][2][3][4][5][6][7][8][9] The common linkers used for constructing 2D COFs are mainly the C=C, CÀ N, C=N, BÀ O and B=N bonds. However, it's still a

Conjugated Polymer-Functionalized 2D MXene Nanosheets for Nonvolatile Memory Devices with High Environmental Stability

“…All the structural characterizations of the as-synthesized materials, device fabrication, and electrical measurements were carried out according to the method described in our previous works. ,− All organic solvents were redistilled under dry nitrogen. All operations were performed under purified argon.…”

Covalent Organic Frameworks for Neuromorphic Devices

“…COF-based resistive switching memories generally possess a metal–insulator–metal (MIM) device structure that enables resistance (conductance) switching between high-resistance state (HRS) and low-resistance state (LRS), demonstrating a nonvolatile memory behavior. ,− ,,− Such simple device architectures facilitate further scaling-down with a crossbar array geometry for high-intensity integration, which is promising for high-density data storage and neuromorphic applications. Generally, the resistance switching mechanisms in organic materials are explained by conductive filament, charge trapping/detrapping, charge transfer, redox reaction, and conformation change …”

“…The redox reactions in COF materials are closely related to the redox-active moieties, such as naphthalenediimide, triphenylamine, tetrathiafulvalene, quinoid, and metal-containing linkers (porphyrins). Typically, cyclic voltammetry (CV) studies have to be carried out to demonstrate the oxidation/reduction process of COF films, thereby confirming the occurrence of electrochemical redox reactions …”

“…Typically, cyclic voltammetry (CV) studies have to be carried out to demonstrate the oxidation/reduction process of COF films, thereby confirming the occurrence of electrochemical redox reactions. 87 Conformational Change. Some polymers with planar-conjugated functional groups can conduct conformational transformation with external electrical stimulus, leading to the conductivity variation.…”

“…In addition, a D−A system can also be achieved in one monomer. Recently, Zhao et al 87 incorporated azulene (Azu) into COF to fabricate memristora composed of Al/COF-Azu/ ITO, where the Azu monomer itself utilizes electron-poor sevenmembered ring and electron-rich five-membered ring to form an electron-accepting and -donating subsystem (Figure 4e). Owing to the D−A feature, the redox-active azulene has large dipole moments to stabilize the conductance state, leading to a nonvolatile memristive behavior.…”