Herein, we describe the synthesis of two highly crystalline, robust, hydrophilic covalent organic frameworks (COFs) that display intrinsic proton conduction by the Grotthuss mechanism. The enriched redox‐active azo groups in the COFs can undergo a proton‐coupled electron transfer reaction for energy storage, making the COFs ideal candidates for pseudocapacitance electrode materials. After in situ hybridization with carbon nanotubes, the composite exhibited a high three‐electrode specific capacitance of 440 F g−1 at the current density of 0.5 A g−1, among the highest for COF‐based supercapacitors, and can retain 90 % capacitance even after 10 000 charge–discharge cycles. This is the first example using Grotthuss proton‐conductive organic materials to create pseudocapacitors that exhibited both high power density and energy density. The assembled asymmetric two‐electrode supercapacitor showed a maximum energy density of 71 Wh kg−1 with a maximum power density of 42 kW kg−1, surpassing that of all reported COF‐based systems.
Efficient propyne/propylene separation
to obtain polymer-grade
propylene is a crucial and challenging process in industrial production,
but it has not yet been realized in the covalent organic framework
(COF) field. Addressing this challenge, we synthesize two three-dimensional
COF adsorbents via a [8 + 4] construction approach based on an octatopic
aldehyde monomer. Upon using the continuous rotation electron diffraction
technique and structural simulation, both COFs are successfully determined
as rare flu topology. Various characterization techniques
prove that both COFs exhibit high crystallinity, high porosity, and
good stability. Attributed to their interconnected micropores and
nonpolar pore environment, these COFs can efficiently remove trace
amounts of propyne from the propyne/propylene (1/99, and 0.1/99.9,
v/v) mixture to obtain high-purity propylene (>99.99%), validated
by dynamic breakthrough experiments. This work paves a new avenue
for propyne/propylene separation using COFs as highly efficient adsorbents.
Developing new materials for anhydrous proton conduction under high-temperature conditions is significant and challenging. Herein, we create a series of highly crystalline covalent organic frameworks (COFs) via a pore engineering approach. We simultaneously engineer the pore geometry (generating concave dodecagonal nanopores) and pore surface (installing multiple functional groups such as À C=NÀ , À OH, À N=NÀ and À CF 3 ) to improve the utilization efficiency and hostguest interaction of proton carriers, hence benefiting the enhancement of anhydrous proton conduction. Upon loading with H 3 PO 4 , COFs can realize a proton conductivity of 2.33 × 10 À 2 S cm À 1 under anhydrous conditions, among the highest values of all COF materials. These materials demonstrate good stability and maintain high proton conductivity over a wide temperature range (80-160 °C). This work paves a new way for designing COFs for anhydrous proton conduction applications, which shows great potential as high-temperature proton exchange membranes.
Developing strategies to enhance the structural robustness
of covalent
organic frameworks (COFs) is of great importance. Here, we rationally
design and synthesize a class of cross-linked COFs (CCOFs),
in which the two-dimensional (2D) COF layers are anchored and connected
by polyethylene glycol (PEG) or alkyl chains through covalent bonds.
The bottom-up fabrication of these CCOFs is achieved by
the condensation of cross-linked aldehyde monomers and tritopic amino
monomers. All the synthesized CCOFs possess high crystallinity
and porosity, and enhanced structural robustness surpassing the typical
2D COFs, which means that they cannot be exfoliated under ultrasonication
and grinding due to the cross-linking effect. Furthermore, the cross-linked
patterns of PEG units are uncovered by experimental results and Monte
Carlo molecular dynamics simulations. It is found that all CCOFs are dominated by vertical cross-layer (interlayer) connections
(clearly observed in high-resolution transmission electron microscopy
images), allowing them to form quasi-three-dimensional (quasi-3D)
structures. This work bridges the gap between 2D COFs and 3D COFs
and provides an efficient way to improve the interlayered stability
of COFs.
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