cm9b02286_si_001.pdf (2.71 MB)
Covalent Organic Framework Films through Electrophoretic DepositionCreating Efficient Morphologies for Catalysis
journal contribution
posted on 2019-12-02, 22:43 authored by Julian
M. Rotter, Simon Weinberger, Jonathan Kampmann, Torben Sick, Menny Shalom, Thomas Bein, Dana D. MedinaThe ability to grow covalent organic framework (COF)
films allows
for studying their properties as solid layers and enables the incorporation
of these materials into a variety of functional devices. Here, we
report on the fabrication of COF films and coatings by electrophoretic
deposition (EPD). We demonstrate that the EPD technique is suitable
for depositing COFs featuring two- and three-dimensional structures
linked by imine or boronate ester bonds, namely, BDT-ETTA COF, COF-300,
and COF-5. For the deposition, COF nanoparticle suspensions are prepared
by dispersing the as-synthesized bulk materials in solvents with low
dielectric constants. Subsequently, two electrodes are immersed into
the COF particle suspensions, and upon inducing electric fields ranging
from 100 to 900 V cm–1, COFs are deposited as films
on the positively charged electrode. Through EPD, within 2 min, large-area
films of up to 25 cm2 are obtained on smooth or corrugated
surfaces. COF films prepared by EPD feature an inherent textural porosity
and tunable thickness, demonstrated from 400 nm to 24 μm. By
controlling the deposition parameters such as duration, particle concentration,
and applied potential, deposits of precise thickness can be produced.
Furthermore, codepositions of different COFs as well as COF/Pt nanoparticles from
mixed suspensions are demonstrated. The film morphologies obtained
by EPD are shown to be advantageous for catalysis, as demonstrated
for sacrificial agent-free photoelectrochemical water reduction. Here,
BDT-ETTA COF photocathodes show a strongly increased photocurrent
density compared to the respective dense and oriented films. Typical
BDT-ETTA COF/Pt nanoparticle hybrid films exhibit photocurrent densities
of over 100 μA cm–2. The rapid and scalable
deposition of COF particles as films and coatings through EPD is a
versatile addition to the toolbox of COF film fabrication techniques,
allowing for tailoring COF film architectures for desired
functionalities.
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BDT-ETTA COF photocathodes showboronate ester bondsCOF particle suspensionsEPDCOF filmsas-synthesized bulk materialsCovalent Organic Framework Filmsfilms exhibit photocurrent densities24 μ mCOF film architecturesCOF film fabrication techniquesagent-free photoelectrochemical water reduction25 cm 2COF nanoparticle suspensions
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