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Two-dimensional
(2D) imine-linked covalent organic frameworks (COFs)
have attracted great interest for gas uptake, catalysis, drug delivery,
electronic devices, and photocatalytic applications. The synthetic
methodologies involved in imine-linked COF formations such as solvothermal
synthesis usually require harsh experimental conditions. In this work,
we show for the first time how highly crystalline COFs with very high
surface areas (3.6 times higher than using conventional approaches)
can be prepared by combining a mechanochemical and crystallization
approach. More importantly, this facile method is a general route
to novel composites of COF and metal oxides including Fe3O4, Co3O4, and NiO. The composites
can be used as magnetically recoverable adsorbents and show a strong
redox-activity making them interesting for applications in electrochemical
energy storage.
Nitrogen-doped carbon aerogels (NCAs) have received great attention for a wide range of applications, from thermal electronics to waste water purification, heavy metal or gas adsorption, energy storage, and catalyst supports. Herein NCAs are developed via the synthesis of a Schiff-base porous organic polymer aerogel followed by pyrolysis. By controlling the pyrolysis temperature, the polymer aerogel can be simply converted into porous NCAs with a low bulk density (5 mg cm −3 ), high surface area (2356 m 2 g −1 ), and high bulk porosity (70%). The NCAs containing 1.8-5.3 wt% N atoms exhibit remarkable CO 2 uptake capacities (6.1 mmol g −1 at 273 K and 1 bar, 33.1 mmol g −1 at 323 K and 30 bar) and high ideal adsorption solution theory selectivity (47.8) at ambient pressure. Supercapacitors fabricated with NCAs display high specific capacitance (300 F g −1 at 0.5 A g −1 ), fast rate (charge to 221 F g −1 within only 17 s), and high stability (retained >98% capacity after 5000 cycles). Asymmetric supercapacitors assembled with NCAs also show high energy density and power density with maximal values of 30.5 Wh kg −1 and 7088 W kg −1 , respectively. The outstanding CO 2 uptake and energy storage abilities are attributed to the ultra-high surface area, N-doping, conductivity, and rigidity of NCA frameworks.
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