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Updated: May 30, 2026
Microfluidic-based Synthesis of Covalent Organic Frameworks (COFs): A Tool for Continuous Production of COF Fibers and Direct Printing on a Surface
Published on: July 10, 2017
Enhanced hydrolytic stability of self-assembling alkylated two-dimensional covalent organic frameworks
Laura M Lanni1, R William Tilford, Muktha Bharathy
1Department of Chemistry and Biochemistry, University of South Carolina, Columbia, 29208, United States.
Alkylation in the pores of covalent organic frameworks (COFs) significantly enhances their stability in aqueous environments. Alkylated COFs show improved structural integrity and porosity retention compared to nonalkylated frameworks, demonstrating a 50-fold increase in stability.
Area of Science:
- Materials Science
- Polymer Chemistry
- Nanotechnology
Background:
- Covalent organic frameworks (COFs) are crystalline porous polymers with tunable properties.
- Boronate ester-linked COFs are susceptible to hydrolysis in aqueous environments, limiting their applications.
- Understanding factors influencing COF stability is crucial for developing robust materials.
Purpose of the Study:
- To investigate the impact of pore alkylation on the stability of two-dimensional boronate ester-linked COFs in aqueous media.
- To compare the hydrolytic stability of alkylated COFs with nonalkylated (bare-pore) COFs.
- To quantify the protective effect of alkylation against hydrolysis and porosity loss.
Main Methods:
- Synthesis and characterization of bare-pore COFs (COF-18Å, COF-5) and alkylated-pore COFs (COF-16Å (methyl), COF-14Å (ethyl), COF-11Å (propyl)).
- Exposure of COFs to aqueous environments (neutral, acidic, basic) and assessment of porosity using BET analysis.
- Monitoring structural integrity and monomer release via SEM, absorbance spectroscopy, and 1H NMR.
- Evaluation of crystallinity changes using X-ray diffraction.
Main Results:
- Nonalkylated COFs (COF-18Å, COF-5) rapidly hydrolyzed in aqueous media, losing nearly all porosity and crystallinity.
- Alkylated COFs (COF-16Å, COF-14Å, COF-11Å) exhibited significantly enhanced stability, with only a ~25% decrease in porosity and ~40% decrease in crystallinity.
- Hydrolysis rate was dependent on pH, being fastest in basic aqueous media.
- COF-11Å (propyl-alkylated) demonstrated up to a 50-fold increase in stability compared to COF-18Å (nonalkylated).
Conclusions:
- Pore alkylation is an effective strategy to enhance the hydrolytic stability of boronate ester-linked COFs.
- Alkylated COFs retain significant porosity and structural integrity in aqueous environments, unlike their nonalkylated counterparts.
- These findings enable the design of more durable COFs for applications requiring exposure to water or humid conditions.
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