What Fluorine Can Do in CO₂ Chemistry: Applications from Homogeneous to Heterogeneous Systems

Abstract

CO 2 chemistry including capture and fixation has attracted great attention towards the aim of reducing the consumption of fossil fuels and CO 2 accumulation in the atmosphere. "CO 2-philic" materials are required to achieve good performance owing to the intrinsic properties of the CO 2 molecule, that is, thermodynamic stability and kinetic inertness. In this respect, fluorinated materials have been deployed in CO 2 capture (physical and chemical pathway) or fixation (thermo-and electrocatalytic procedure) with good performances, including homogeneous (e. g., ionic liquids and small organic molecules) and heterogeneous counterparts (e. g., carbons, porous organic polymers, covalent triazine frameworks, metal-organic frameworks, and membranes). In this Minireview, these works are summarized and analyzed from the aspects of (1) the strategy used for fluorine introduction, (2) characterization of the targeted materials, (3) performance of the fluorinated systems in CO 2 chemistry, and comparison with the nonfluorinated counterparts, (4) the role of fluorinated functionalities in the working procedure, and (5) the relationship between performance and structural/electronic properties of the materials. The systematic summary in this Minireview will open new opportunities in guiding the design of "CO 2-philic" materials and pave the way to stimulate further progress in this field.

Highly Perfluorinated Covalent Triazine Frameworks Derived from a Low‐Temperature Ionothermal Approach Towards Enhanced CO2 Electroreduction

“…Elemental analysis is conducted to determine the elemental composition of F‐CTF, which contains 48 wt % C, 18 wt % N, and 31 wt % F, and is very close to the theoretical values (Table S1). Notably, the F content in the resulting F‐CTF‐1‐275 herein is the highest among all the fluorinated CTF materials being stated so far [41] . Fourier‐transform infrared (FTIR) spectroscopy of F‐CTF (Figure 3 D) exhibited the characteristic bands for aromatic rings (994, 1471, and 1608 cm −1 for C=C), triazine rings (1349 cm −1 for C−N and 1703 cm −1 for C=N), and C−F bond (1044 cm −1 ).…”

Highly Perfluorinated Covalent Triazine Frameworks Derived from a Low‐Temperature Ionothermal Approach Towards Enhanced CO2 Electroreduction

“…Notably, the F content in the resulting F-CTF-1-275 herein is the highest among all the fluorinated CTF materials being stated so far. [41] Fourier-transform infrared (FTIR) spectroscopy of F-CTF (Figure 3 D) exhibited the characteristic bands for aromatic rings (994, 1471, and 1608 cm À1 for C=C), triazine rings (1349 cm À1 for CÀN and 1703 cm À1 for C=N), and CÀF bond (1044 cm À1 ). In addition, there are no signals around 2230 cm À1 , indicating no residual -CN exists and the high catalytic activity of Zn(NTf 2 ) 2 in the trimerization process.…”

Graphitic Aza‐Fused π‐Conjugated Networks: Construction, Engineering, and Task‐Specific Applications

“…Incorporation of fluorine moieties within the skeleton of CTF materials could improve their CO 2 adsorption/separation capabilities via the electrostatic interactions of the polar CF bonds and CO 2 molecules. [ 129 ] Han's group first produced F‐CTFs using tetrafluoroterephthalonitrile (TFPN, Figure 3) as the monomer via the ZnCl 2 ‐catalyzed trimerization procedure. [ 35 ] For example, F‐CTF‐1‐600 obtained at 600 °C had a surface area of 1535 m 2 g −1 .…”