What Makes Fluorinated MOFs Superior?

What Are Fluorinated MOFs?

Fluorinated metal-organic frameworks (F-MOFs) are a class of porous crystalline materials consisting of metal ions or clusters coordinated with fluorinated organic ligands. By adding fluorine to MOFs, researchers achieve better stability and enhanced hydrophobic characteristics along with versatile functionality, which makes these materials ideal for multiple applications, including gas storage and separation technology as well as catalysis and energy storage solutions and environmental cleanup. The presence of fluorine atoms modulates the electronic structure and pore size while altering surface chemistry to deliver tunable characteristics that outperform traditional MOFs.

The synthesis of F-MOFs generally involves solvothermal or hydrothermal methods that utilize fluorinated linkers to coordinate with metal centers. The produced structures demonstrate high porosity while remaining thermally stable and resistant to chemical degradation, especially when exposed to humid or acidic conditions.

Fig.1 Molecular structures of the fluorinated linkers^[1].

Fig.2 F-MOF-x was synthesized using the H₂FBBA method^[2].

How Does Fluorination Affect the Properties of MOFs?

• Enhanced Stability

MOFs become more stable against moisture, heat, and chemical degradation through fluorination. The robust C-F bond combined with fluorine's electron-withdrawing characteristics lowers the chemical reactivity of the framework, which prevents hydrolysis and structural collapse when exposed to moisture-rich conditions. For example, fluorinated ZIFs (zeolitic imidazolate frameworks) keep their crystalline structure and porous nature under high humidity conditions while non-fluorinated variants degrade quickly.

Property	Effect of Fluorination
Water Stability	Improved due to hydrophobicity
Thermal Stability	Increased resistance to decomposition
Chemical Resistance	Enhanced tolerance to acids and bases

• Modulation of Pore Structure and Porosity

The addition of fluorine alters both the distribution of pore sizes and the overall surface area. The use of fluorinated ligands leads to enhanced porosity by preventing framework collapse and supporting the formation of micropores. Some F-MOFs, such as MIL-47-F and Al-MIL-53-F, exhibit modified pore architectures that enhance selective molecular adsorption.

• Improved Adsorption and Selectivity

MOFs with fluorine functionalization show enhanced adsorption efficiency, especially when used for gas separation processes. Introducing fluorine into structures improves selective interaction with designated gas molecules. For instance, Ce-F4MIL140A shows exceptional selectivity toward CO₂ whereas SIFSIX materials demonstrate excellent separation capabilities between C3H4 and C3H6.

• Hydrophobicity and Low Dielectric Properties

MOFs gain hydrophobic properties through fluorination, which helps minimize water absorption and prolongs their operational life in water-rich settings. This characteristic proves beneficial for electronic applications because they need materials with low dielectric constants (κ).

What Are the Key Applications of Fluorinated MOFs?

Gas Storage and Separation

Due to their hydrophobic properties and adjustable pore sizes, the use of fluorinated MOFs is common in gas adsorption and separation processes. Applications include:

• Carbon Capture: F-MOFs including Ce-F4MIL140A display strong CO₂ adsorption characteristics and selectivity, which lower greenhouse gas emissions.
• Methane and Hydrogen Storage: F-MOFs show efficient storage capabilities for CH4 and H₂, which makes them promising for clean energy uses.
• Selective Gas Separation: DNL-9(Fe) materials enable separation of C2H₂ from C2H4 even when humidity is present, and they perform better than traditional adsorbents.

Fig.3 CO₂/SO₂ capture performance of KAUST-7^[3].

Catalysis and Reaction Acceleration

F-MOFs achieve better catalytic efficiency because of their distinctive electronic and structural properties. Notable catalytic applications include:

• Diels-Alder Reactions: Perfluorinated MOFs show excellent catalytic performance during cycloaddition processes.
• Aromatic C-H Iodination: F-MOFs enable selective halogenation processes, which create efficient organic synthesis routes.
• Chiral and Multifunctional Catalysis: F-MOFs with functional groups serve as chiral catalysts that enhance enantioselectivity in asymmetric chemical reactions.

Energy Storage and Conversion

Functionalized F-MOFs drive progress in energy storage technology and electrochemical systems through multiple applications.

• Supercapacitors and Lithium-ion Batteries: Fluorinated frameworks improve ion transport mechanisms and maintain cycling stability.
• Photocatalytic and Electrocatalytic Applications: Through their chemical structure, F-MOFs support effective water splitting alongside CO₂ reduction and H₂ production.

Environmental Remediation

F-MOFs are useful for pollution control because they demonstrate powerful adsorption abilities.

• Water Purification: F-MOFs demonstrate effective performance in extracting perfluorooctanoic acid (PFOA) and various persistent organic pollutants from water systems.
• Air Filtration: These materials selectively capture toxic gases such as SO₂, which improves air quality control systems.

Biomedical and Drug Delivery Applications

F-MOFs demonstrate potential as drug carriers due to their biocompatibility and customizable pore structures.

• Controlled Drug Release: Through the control of drug diffusion rates, F-MOFs enhance therapeutic performance.
• Bioimaging and Sensing: The application of functionalized F-MOFs in imaging technologies enables real-time diagnostic capabilities.

Sensors and Chemical Detection

Fluorinated MOFs demonstrate exceptional sensitivity and selectivity when used for chemical sensing tasks.

• Gas and Liquid Sensors: F-MOFs function as detectors for both volatile organic compounds (VOCs) and hazardous gases.
• Nonlinear Optical Sensors: These materials enable advanced photonic applications.

Electronic and Material Science Applications

The scientific community applies F-MOFs for advanced material science developments.

• Dielectric Materials: Low-κ fluorinated MOFs are essential for microelectronics and circuit design.
• Insulation and Coatings: Their chemical resistance makes them suitable for protective coatings.

Alfa Chemistry provides a wide range of fluorinated MOFs. Customers can choose the appropriate fluorinated MOFs according to their own needs. At the same time, we can also provide product customization services according to the detailed requirements of customers. Please contact us, if you are in need of assistance.

References

1. Venturi D M., et al. (2023). "Recent advances in the chemistry and applications of fluorinated metal–organic frameworks (F-MOFs)." RSC Adv. 13, 29215-29230.
2. Pachfule P., et al. (2020). "Synthesis and structural comparisons of five new fluorinated metal organic frameworks (F-MOFs)." CrystEngComm. 12, 1600.
3. Tchalala M R., et al. (2019). "Fluorinated MOF platform for selective removal and sensing of SO₂ from flue gas and air." Nature Communications. 10, 1328.