All‐in‐One Hollow Flower‐Like Covalent Organic Frameworks for Flexible Transparent Devices

Abstract

Covalent organic frameworks (COFs) exhibit great potential in the application of functional electronic devices. However, there has been no report of the precise fabrication of 3D all-in-one hollow micro/nanostructures based on COFs. Here, for the first time, all-in-one hollow dioxin-based COF-316 microflowers are synthesized measuring 5-7 µm and with interconnected hollow petals through a self-template strategy. The growth mechanism involves the collaborative process of self-assembly of nanoparticles, inside-out Ostwald ripening, and epitaxial growth. Due to the intrinsic porosity and interconnected hollow structure, COF-316 can uniformly composite with polypyrrole (PPy) through the "interior" and "exterior" functionalization, in which the hydrogen bond interaction enhances the charge transfer efficiency and structural stability in the charge/discharge process. The COF-316@PPy flexible transparent supercapacitors exhibit an areal specific capacitance (C A ) of 783.6 µF cm -2 at 3 µA cm -2 and longterm cycling stability. This work will boost research on the valuable design concepts of 3D hollow COF materials for energy storage devices.

Controllable Synthesis of Hollow Microtubular Covalent Organic Frameworks as an Enzyme-Immobilized Platform for Enhancing Catalytic Activity

“…33 A Pyrex tube was charged with Tat (21.3 mg, 0.06 mmol) and Dha (15 mg, 0.09 mmol) in a combined solvent of mesitylene (1.7 mL) and dioxane (0.3 mL). Subsequently, 0.1 mL of HAc with different concentrations (12,16, and 17.4 M) was added. After sonication for 5 min, the tube was quickly frozen at a liquid nitrogen bath and degassed.…”

“…Covalent organic frameworks (COFs), as an emerging type of crystalline porous materials, are synthesized by a reversible condensation reaction of organic building blocks. 1,2 Compared with inorganic materials, COFs encompass a large variety of physicochemical properties, involving a low density, high level of porosity, regular/tunable pore size, and good structural stability, which has recently received extensive attention in the fields of separation, 3−7 catalysis, 8,9 sensing, 10,11 energy storage, 12,13 and drug delivery. 14 It is generally recognized that structure−property relationships are decisive features for their applications.…”

“…Covalent organic frameworks (COFs), as an emerging type of crystalline porous materials, are synthesized by a reversible condensation reaction of organic building blocks. , Compared with inorganic materials, COFs encompass a large variety of physicochemical properties, involving a low density, high level of porosity, regular/tunable pore size, and good structural stability, which has recently received extensive attention in the fields of separation, − catalysis, , sensing, , energy storage, , and drug delivery . It is generally recognized that structure–property relationships are decisive features for their applications. , Thus far, various morphologies of COFs have been synthesized, such as films, sheets, spheres, and tubes. , Among them, the tubular COFs have attracted increasing interest in recent years due to their high surface-to-volume ratio, short mass transport path, and high loading capacity .…”

Facile Self-Template Synthesis of a Nitrogen-Rich Nanoporous Carbon Wire and Its Application for Energy Storage Devices

“…Additionally, nanometer-sized carbon spheres, sheets, and wires can provide short ion diffusion paths, significantly improving the specific capacitance . Wang et al synthesized hollow dioxin-based COF-316 microflowers through the self-templated strategy in one step . The “interior” and “exterior” functionalization enhances the charge transfer efficiency and structural stability due to the intrinsic porosity and interconnected hollow structure.…”

“…11 Wang et al synthesized hollow dioxin-based COF-316 microflowers through the selftemplated strategy in one step. 12 The "interior" and "exterior" functionalization enhances the charge transfer efficiency and structural stability due to the intrinsic porosity and interconnected hollow structure. The resulting flexible transparent supercapacitors portray an areal specific capacitance of 783.6 μF cm −2 at 3 μA cm −2 and long-term cycling stability.…”