Enhanced surface area and reduced pore collapse of methylated, imine-linked covalent organic frameworks

Dautzenberg, Ellen; Lam, Milena; Li, Guanna; Smet, Louis C. P. M. de

doi:10.1039/d1nr05911d

Cited by 12 publications

(37 citation statements)

References 26 publications

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“…Structures of the aldehyde nodes (top left), amine linkers (bottom left), and matrix of the synthesized COFs (right)plain blue: published in peer-reviewed literature before, ,− blue diagonal stripes upward: synthesis reported in a patent and characterization data not shown, plain green: novel COFs, green diagonal stripes downward: published by our group …”

Section: Resultsmentioning

confidence: 99%

“…We synthesized a full range of COFs with (a) methylated (Me 3 TFB) and non-methylated (TFB) aldehyde nodes and (b) varying numbers of methyl groups on two different amine linkers (1,4-phenyleneamine derivatives: PA, Me 2 PA, and 16 �we also synthesized the COFs that have been published before (TFB−Me 2 PA, 26 TFB−Me 4 PA, 27 and TFB−Me 2 BD 28 ), completing the matrix in Figure 1 and facilitating a direct comparison (Tables S1−S8). Synthesis and Characterization of COFs.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…The authors found that the more pronounced push−pull effect leads to the lower resulting band gap. Combined with the earlier reported increased stability of methyl-substituted COFs, 16 these two studies motivated us to systematically investigate the effect of methyl groups on the porosity and UV absorbance of iminebased COFs. To this end and given their pore stability and utilization potential of their UV absorbance, we decided to introduce an increasing number of methyl groups, this time also in the amine linkers.…”

Section: ■ Introductionmentioning

confidence: 99%

“…have found that COFs consisting of 2,4,6-trimethylbenzene-1,3,5-carbaldehyde (Me 3 TFB) lead to more robust frameworks compared to non-methylated 1,3,5-benzenetricarbaldehyde (TFB). 16 While COF stability is essential for virtually all applications, other properties, like selectivity and catalytical performance, require tailor-made approaches. Identification of structure− property relationships of COFs would facilitate the process of controlling such properties.…”

Section: ■ Introductionmentioning

confidence: 99%

“…Feriante et al and Zhu and Verduzco both reported a methoxy-functionalized, imine-based COF, which was less prone to pore collapse compared to the initial unfunctionalized COF. Recently, we have found that COFs consisting of 2,4,6-trimethylbenzene-1,3,5-carbaldehyde (Me 3 TFB) lead to more robust frameworks compared to non-methylated 1,3,5-benzenetricarbaldehyde (TFB) …”

Section: Introductionmentioning

confidence: 99%

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Tuning UV Absorption in Imine-Linked Covalent Organic Frameworks via Methylation

et al. 2022

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Covalent organic frameworks (COFs) are porous materials with high surface areas, making them interesting for a large variety of applications including energy storage, gas separation, photocatalysis, and chemical sensing. Structural variation plays an important role in tuning COF properties. Next to the type of the building block core, bonding directionality, and linking chemistry, substitution of building blocks provides another level of synthetic control. Thorough characterization and comparison of various substitution patterns is relevant for the molecular engineering of COFs via rational design. To this end, we have systematically synthesized and characterized multiple combinations of several methylated and non-methylated building blocks to obtain a series of imine-based COFs. This includes the experimental assignment of the COF structure by solid-state NMR. By comparing the properties of all COFs, the following trends were found: (1) upon methylation of the aldehyde nodes, COFs show increased Brunauer−Emmett−Teller surface areas, reduced pore collapse, blue-shifted absorbance spectra, and ∼0.2 eV increases in their optical band gaps. (2) COFs with dimethylated amine linkers show a lower porosity. (3) In tetramethylated amine linkers, the COF porosity even further decreases, the absorbance spectra are clearly red-shifted, and smaller optical band gaps are obtained. Our study shows that methyl substitution patterns on COF building blocks are a handle to control the UV absorbance of the resulting frameworks.

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Section: Resultsmentioning

confidence: 99%

Section: ■ Results and Discussionmentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Tuning UV Absorption in Imine-Linked Covalent Organic Frameworks via Methylation

et al. 2022

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DFT Study of Imine‐Exchange Reactions in Iron(II)‐Coordinated Pincers

van Dam,

van Schendel,

Gangarapu

et al. 2023

Chemistry A European J

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The imine bond is among the most applied motifs in dynamic covalent chemistry. Although its uses are varied and often involve coordination to a transition metal for stability, mechanistic studies on imine exchange reactions so far have not included metal coordination. Herein, we investigated the condensation and transimination reactions of an Fe2+‐coordinated diimine pyridine pincer, employing wB97XD/6‐311G(2d,2p) DFT calculations in acetonitrile. We first experimentally confirmed that Fe2+ is strongly coordinated by these pincers, and is thus a justified model ion. When considering a four‐membered ring‐shaped transition state for proton transfers, the required activation energies for condensation and transimination reaction exceeded values expected for reactions known to be spontaneous at room temperature. The nature of the incoming and exiting amines and the substituents on the para‐position of the pincer had no effect on this. Replacing Fe2+ with Zn2+ or removing it altogether did not reduce it either. However, addition of two ethylamine molecules lowered the energy barriers to be compatible with experiment (19.4 and 23.2 kcal/mol for condensation and transimination, respectively). Lastly, the energy barrier of condensation of a non‐coordinated pincer was significantly higher than found for Fe2+‐coordinating pincers, underlined the catalyzing effect of metal coordination on imine exchange reactions.

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Highly stable β-ketoenamine-based covalent organic frameworks (COFs): synthesis and optoelectrical applications

Liu

et al. 2022

Front. Optoelectron.

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Covalent organic frameworks (COFs) are one class of porous materials with permanent porosity and regular channels, and have a covalent bond structure. Due to their interesting characteristics, COFs have exhibited diverse potential applications in many fields. However, some applications require the frameworks to possess high structural stability, excellent crystallinity, and suitable pore size. COFs based on β-ketoenamine and imines are prepared through the irreversible enol-to-keto tautomerization. These materials have high crystallinity and exhibit high stability in boiling water, with strong resistance to acids and bases, resulting in various possible applications. In this review, we first summarize the preparation methods for COFs based on β-ketoenamine, in the form of powders, films and foams. Then, the effects of different synthetic methods on the crystallinity and pore structure of COFs based on β-ketoenamine are analyzed and compared. The relationship between structures and different applications including fluorescence sensors, energy storage, photocatalysis, electrocatalysis, batteries and proton conduction are carefully summarized. Finally, the potential applications, large-scale industrial preparation and challenges in the future are presented. Graphical Abstract

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Enhanced surface area and reduced pore collapse of methylated, imine-linked covalent organic frameworks

Abstract: Methylation of aldehyde nodes in Covalent Organic Frameworks leads to enhanced BET surface areas and reduced pore collapse compared to their non-methylated counterparts, which has been rationalized by DFT computations.

Cited by 12 publications

References 26 publications

Tuning UV Absorption in Imine-Linked Covalent Organic Frameworks via Methylation

Tuning UV Absorption in Imine-Linked Covalent Organic Frameworks via Methylation

DFT Study of Imine‐Exchange Reactions in Iron(II)‐Coordinated Pincers

Highly stable β-ketoenamine-based covalent organic frameworks (COFs): synthesis and optoelectrical applications

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