Fluorine‐Containing Covalent Organic Frameworks: Synthesis and Application

Abstract

Covalent organic frameworks (COFs) are a type of crystalline porous polymers that possess ordered structures and eternal pores. Because of their unique structural characteristics and diverse functional groups, COFs have been used in various application fields, such as adsorption, catalysis, separation, ion conduction, and energy storage. Among COFs, the fluorine‐containing COFs (fCOFs) have been developed for special applications by virtue of special physical and chemical properties resulting from fluorine element, which is a nonmetallic halogen element and possesses strong electronegativity. In the organic chemistry field, introducing fluorine into chemicals enables those chemicals to exhibit many interesting properties, and fluorine chemistry increasingly plays an important role in the history of chemical development. The introduction of fluorine in COFs can enhance the crystallinity, porosity, and stability of COFs, making COFs having superior performances and some new applications. In this review, the synthesis and application of fCOFs are systematically summarized. The application involves photocatalytic production of hydrogen peroxide, photocatalytic water splitting, electrocatalytic CO2 reduction, adsorption for different substances (H2, pesticides, per‐/polyfluoroalkyl substances, polybrominated diphenyl ethers, bisphenols, and positively charged organic dye molecules), oil−water separation, energy storage (e.g., zinc‐ion batteries, lithium−sulfur batteries), and proton conduction. Perspectives of remaining challenges and possible directions for fCOFs are also discussed.

Trifluoromethyl-Functionalized 2D Covalent Organic Framework for High-Resolution Separation of Isomers

“…The weaker crystallinity may cause the smaller pore volume of TbTFMB. Compared with TpBD, TpTFMB showed worse crystallinity, likely due to the steric effect from the large group of −CF 3 , but larger specific surface area and pore volume, probably owing to the self-complementary π-electronic interaction provided by the introduction of fluorine. − …”

Unravelling the structure of CO2 in silica adsorbents: an NMR and computational perspective

“…Using this approach, it was possible to obtain new information on the nature of CO 2 chemisorbed species in AMPS sorbents, 50 reinforcing the potential of other isotope labelling schemes such as 15 N and 19 F into the organic moieties of porous adsorbents. For instance, introducing fluorine atoms may not only confer improved chemical stability to the sorbent [52][53][54] but also significantly enhance CO 2 adsorption capacity and selectivity in CO 2 /N 2 gas mixtures, while maintaining the NMR sensitivity conferred by the high natural abundance of 19 F isotopes. 55 The replacement of hydrogen with fluorine atoms also enhances the hydrophobicity of the materials rendering this choice more attractive for applications under moist conditions where water competes with other gases for the same adsorption sites.…”

Nanoporous Metal/Covalent Organic Framework-Based Electrocatalysts for Water Splitting

“…These attributes render FCOFs applicable in various field, including photocatalytic water splitting, electrolytic CO 2 reduction, and adsorption of various substances. 145 In pursuit of creating COFs with high conductivity and long durability, Feng et al prepared a COF functionalized with a sulfonic group (COF-SO 3 ) that exhibits high conductivity. This catalyst finds applications in lithium sulfur batteries and as an electrocatalyst toward OER, and it displays lower overpotential as compared to other COFs.…”

“…The resulting fluorinated COF (FCOF) showcases notable features including high stability, increased surface area, improved crystallinity, and high porosity. These attributes render FCOFs applicable in various field, including photocatalytic water splitting, electrolytic CO 2 reduction, and adsorption of various substances . In pursuit of creating COFs with high conductivity and long durability, Feng et al.…”