Polyarylether‐Based 2D Covalent‐Organic Frameworks with In‐Plane D–A Structures and Tunable Energy Levels for Energy Storage

Abstract

The robust fully conjugated covalent organic frameworks (COFs) are emerging as a novel type of semi‐conductive COFs for optoelectronic and energy devices due to their controllable architectures and easily tunable the highest occupied molecular orbital (HOMO) and the lowest occupied molecular orbital (LUMO) levels. However, the carrier mobility of such materials is still beyond requirements due to limited π‐conjugation. In this study, a series of new polyarylether‐based COFs are rationally synthesized via a direct reaction between hexadecafluorophthalocyanine (electron acceptor) and octahydroxyphthalocyanine (electron donor). These COFs have typical crystalline layered structures, narrow band gaps as low as ≈0.65 eV and ultra‐low resistance (1.31 × 10−6 S cm−1). Such COFs can be composed of two different metal‐sites and contribute improved carrier mobility via layer‐altered staking mode according to density functional theory calculation. Due to the narrow pore size of 1.4 nm and promising conductivity, such COFs and electrochemically exfoliated graphene based free‐standing films are fabricated for in‐plane micro‐supercapacitors, which demonstrate excellent volumetric capacitances (28.1 F cm−3) and excellent stability of 10 000 charge–discharge cycling in acidic electrolyte. This study provides a new approach toward dioxin‐linked COFs with donor‐acceptor structure and easily tunable energy levels for versatile energy storage and optoelectronic devices.

Enabling Multi-Chemisorption Sites on Carbon Nanofibers Cathodes by an In-situ Exfoliation Strategy for High-Performance Zn–Ion Hybrid Capacitors

“…S5b). These results show that nitric acid oxidation reduces the relative concentration of alcohol groups on the surface of carbon nanofibers and promotes the formation of carbonyl groups [ 35 , 36 ]. Since carbonyl oxygen is the most effective electron absorbing group among the three oxygen groups, the increase of the proportion of carbonyl makes part of the electron density of alcohol group taken away by carbonyl oxygen, which leads to the whole O 1 s peak position of N-OPCNF moving to a higher binding energy [ 37 ].…”

An Initial Covalent Organic Polymer with Closed‐F Edges Directly for Proton‐Exchange‐Membrane Fuel Cells

“…Noteworthily, the slight deviation for fluorine position of COP BTC ‐F compared with TFP monomer is attributed to the effect of the polymerization of cyano groups in the TFP monomer to form coordination on the closed‐F edges, convincingly confirming that TFP monomer is fully involved in the polymerization. [ 71 ] In addition, the peak located at 687.315 eV in F 1s XPS spectra is assigned to the FC bond, likewise manifesting that F functionalities were successfully doped into the edge of COP BTC ‐F skeleton (Figure S3 and Table S1, Supporting Information). Gel permeation chromatography measurement analysis (Figure 1c) was carried out to quantitatively evaluate the degree of polymerization of the as‐synthesized COP BTC ‐F sample.…”

“…Exclusive four F functionalities in the TFP monomer serve as dopant sources, decorating into the closed edge of the COP BTC ‐F skeleton by polymerizing extra two cyano groups of TFP monomer, confirmed by the 19 F solid‐state NMR spectra (Figure 1b). COP BTC ‐F exhibits chemical shifts almost resemble to that of the TFP monomer (−141.08 and −122.21 ppm) [ 71–73 ] whereas the rest of the peaks in the spectra originate from the spinning side band unique to 19 F solid‐state NMR spectra. Noteworthily, the slight deviation for fluorine position of COP BTC ‐F compared with TFP monomer is attributed to the effect of the polymerization of cyano groups in the TFP monomer to form coordination on the closed‐F edges, convincingly confirming that TFP monomer is fully involved in the polymerization.…”

Modulating electronic structure of triazine-based covalent organic frameworks for photocatalytic organic transformations

“…Covalent organic frameworks (COFs) are a new class of crystalline porous organic materials with high stability, low density, large specific surface area and permanent porosity. 22,23 Benefiting from these features, COFs have emerged as promising platforms for potential applications in membrane separation, 24,25 luminescence 26 and sensors, 27 proton conduction, 28,29 energy storage 30,31 and heterogeneous catalysis. 32–34 In particular, 2D COFs have great advantages in heterogeneous catalysis, including: (i) the band gap and visible light absorption ability of 2D COFs can be easily adjusted by changing the building block; 35 (ii) the ordered π-conjugated structure and π–π stacking in inter-layers are in favour of delocalization of electrons; 36,37 (iii) 2D COFs offer a unique 1D nanopore channel, and the charges can transfer to the surface of the catalyst through this channel; 38 (iv) benefiting from the introduction of donor (D) and acceptor (A) components in 2D COFs, the constructed COFs possess effective separation of electron–hole pairs.…”