Cyano Substituent on the Olefin Linkage: Promoting Rather than Inhibiting the Performance of Covalent Organic Frameworks

Abstract

It is generally believed that the electron-withdrawing cyano group in the olefin linkage would inhibit the stability and πconjugation of covalent organic frameworks (COFs), which raises concerns about their optoelectronic properties. However, the structure−activity relationship between the structure of olefin linkages and properties of COFs is still inconclusive. In this work, imine-, vinylene-, and acrylonitrile-linked COFs with identical triphenyltriazine building blocks were designed and synthesized. Our work demonstrated that construction of acrylonitrile linkages not only enhanced the chemical stability and photostability but also led to remarkable optoelectronic properties with a record fluorescence quantum yield of 35.37% in the solid state. Further, the acrylonitrile linkage endows TTAN-COF/Pt NPs with superior and durable photocatalytic activity in both the hydrogen evolution reaction (11.94 mmol g −1 h −1 ; BET surface area, 739.28 m 2 g −1 ) and aerobic oxidation reaction. This work demonstrates that the acrylonitrile linkage can significantly enhance the optoelectronic properties and photocatalytic activities of COFs compared with the highly π-conjugated vinylene linkage, providing a valuable reference for the design of optoelectronic functional materials.

Ligand regulation strategy of COF-based photocatalyst for ROS-mediated RAFT polymerization

“…S5d†). 33,35 The above results reveal that introducing the electron donor group appended to the pore wall improves the photoelectric conversion performance of the COF.…”

“…This is contrary to traditional photocatalysts where the higher the fluorescence intensity, the weaker the catalytic performance. 33 Additionally, PPEGMA served as a macroinitiator to produce block polymers PPEGMA- b -PHPMA under open-to-air conditions (Fig. S6†).…”

“…In general, the conduction band (CB) position was close to the flat band potential in n-type semiconductors. 33 Thus, the CB positions of TAPT-TP-COF, TAPT-DMTA-COF, TAPT-DMTA/TP-COF and TAPT-DHTA-COF were estimated to be −0.47, −0.94, −0.98 and −0.68 V versus NHE, and the valence band (VB) positions were calculated to be 1.93, 1.26, 1.47 and 1.05 V, respectively, according to the formula E CB = E VB − E g (Fig. 1g).…”

Hydroxy-Containing Covalent Organic Framework Combined with Nickel Ferrite as a Platform for the Recognition and Capture of Bisphenols

“…43 This type of isotherm has also been observed in several COFs. 44,45 Figure S15a reveals that NiFe 2 O 4 @COF possessed a type IV isotherm according to the IUPAC classification, which is a characteristic of a mesoporous material. The BET model was used to measure the surface areas, which were determined to be 244.20 m 2 g −1 for the COF and 109.73 m 2 g −1 for NiFe 2 O 4 @COF.…”

Recent advances on covalent organic frameworks (COFs) as photocatalysts: different strategies for enhancing hydrogen generation

“…By choosing building blocks with similar skeleton structures as knots, but with different linkages to investigate HER property is necessary (Table 2). [95][96][97] To this end, Yu and co-authors adopted triphenylbenzene knots and phenyl linkers to explore the effect of three structurally similar COFs with distinct linkages on the photocatalytic hydrogen precipitation performance. 95 The experiments revealed that the HER activity could be tuned with the rate in the order of COF-olefin (2.33 mmol g À1 h À1 ) c COFimide (o40 mmol g À1 h À1 ) 4 COF-imine (o40 mmol g À1 h À1 ).…”