Crystalline Covalent Triazine Frameworks by In Situ Oxidation of Alcohols to Aldehyde Monomers

Abstract

Covalent triazine frameworks (CTFs) with aromatic triazine linkages have recently received increasing interest for various applications because of their rich nitrogen content and high chemical stability.O wing to the strong aromatic C=N bond and high chemical stability,o nly af ew CTFs are crystalline,a nd most CTFs are amorphous.H erein we report anew general strategy to give highly crystalline CTFs by in situ formation of aldehyde monomers through the controlled oxidation of alcohols.T his general strategy allows as eries of crystalline CTFs with different monomers to be prepared, which are shown to have higher thermal stability and enhanced performance in photocatalysis as compared with the less crystalline or amorphous CTFs.This open-system approach is very simple and convenient, which presents ap otential pathway to large-scale industrial production of crystalline CTFs.

Conjugated polymers for visible-light-driven photocatalysis

“…137 Besides the above-mentioned amorphous CTFs, Tan and coworkers reported the successful preparation of crystalline CTFs 64-66 by in situ oxidizing alcohols into aldehyde monomers and studied their H 2 production activities. 138 It was claimed that high crystallinity of CTFs could be achieved by slowing down their nucleation process through controlling aldehyde monomer generation in the polycondensation reaction. All CTFs showed good crystallinity with BET surface areas of 520-599 m 2 g À1 .…”

Solving the COF trilemma: towards crystalline, stable and functional covalent organic frameworks

“…51,53 These extremely harsh conditions lead to partial carbonization of the materials and low crystallinity. 54 Milder conditions are achieved by using superacid catalysis with trifluoromethanesulfonic acid or by the formation of the triazine unit from multifunctional benzyl alcohols that react with amidines, by slow in situ oxidation. 54,55 Such conditions lead to very stable materials, but make for poor functional group tolerance.…”

“…54 Milder conditions are achieved by using superacid catalysis with trifluoromethanesulfonic acid or by the formation of the triazine unit from multifunctional benzyl alcohols that react with amidines, by slow in situ oxidation. 54,55 Such conditions lead to very stable materials, but make for poor functional group tolerance. Further, the crystallinity of CTFs is typically limited, and so far only a few out of the many reported CTF materials are crystalline.…”

“…The slow oxidation by air to the aldehyde during the reaction served as a means to supply the precursor at a controlled rate, enabling the formation of a crystalline framework. 54 Alternately, crystalline CTFs were obtained from amidine and aldehyde building blocks by slow addition to the reaction mixture by controlling the speed of a peristaltic pump. 118 The crystallinity increased with slower feed rates and in the TEM large ordered crystallites are visible in addition to the PXRD, while the direct solution synthesis produced a material with a much lower crystallinity (Fig.…”

Immobilized covalent triazine frameworks films as effective photocatalysts for hydrogen evolution reaction

“…CTFs are constructed by covalently linking light elements (C, N, and H), which exhibit intriguing physical/ chemical properties such as high porosity, high nitrogen content, and good thermal/chemical stability [1][2][3] . These unique properties endow CTFs with great prospects in various applications including gas separation and storage, energy storage, and photo/ electro/thermo-catalysis [4][5][6][7][8][9] . In the development of CTFs, substantial improvement has been made in the preparation method and crystallinity, but the processability problem still limits its practical applications.…”