Solvothermal depolymerization and recrystallization of imine-linked two-dimensional covalent organic frameworks

Ji, Woojung; Hamachi, Leslie S.; Natraj, Anusree; Flanders, Nathan C.; Li, Rebecca L.; Chen, Lin X.; Dichtel, William R.

doi:10.1039/d1sc03963f

Cited by 20 publications

(20 citation statements)

References 41 publications

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“…Based on SEM images of drop-cast aliquots of the TAPB-DMPDA COF polymerizations isolated at different reaction times, the crystals reached their final sizes within 6 min (Figure S19A). We hypothesized that increasing the reaction temperature would slow nucleation based on our recent study of COF recrystallization 53 and the temperaturedependence of the imine/aldehyde equilibrium. Indeed, a polymerization temperature of 150 °C produced TAPB-DMPDA COF crystals of up to 20 μm in size.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…Early mechanistic studies of imine-based 2D polymerizations suggested that the rapid formation of a polymer network followed by crystallization by imine exchange reactions occurred under most solvothermal conditions . More recently, imine-linked COF formation was found to be rapid , and, in some cases, thermally reversible, and two examples of micron-size and larger imine-linked 2D COF single crystals have been reported. , Wei and coworkers reported millimeter-sized crystals of an imine-linked 2D COF, TAPPy-PDA , using supercritical CO 2 as the reaction solvent and reaction times as short as 5 min, although the crystallinity was characterized by transmission electron microscopy (TEM) analysis rather than bulk X-ray diffraction . This 2D polymer had been reported previously as a polycrystalline powder by Bein and coworkers under traditional solvothermal conditions and reaction times of 1–3 days .…”

Section: Introductionmentioning

confidence: 99%

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Single-Crystalline Imine-Linked Two-Dimensional Covalent Organic Frameworks Separate Benzene and Cyclohexane Efficiently

et al. 2022

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Two-dimensional (2D) covalent organic frameworks (COFs) are composed of structurally precise, permanently porous, layered macromolecular sheets, which are traditionally synthesized as polycrystalline solids with crystalline domain lengths smaller than 100 nm. Here, we polymerize imine-linked 2D COFs as suspensions of faceted single crystals in as little as 5 min at moderate temperature and ambient pressure. Single crystals of two imine-linked 2D COFs were prepared, consisting of a rhombic 2D COF (TAPPy-PDA) and a hexagonal 2D COF (TAPB-DMPDA). The sizes of TAPPy-PDA and TAPB-DMPDA crystals were tuned from 720 nm to 4 μm and 450 nm to 20 μm in width, respectively. High-resolution transmission electron microscopy revealed that the COF crystals consist of layered, 2D polymers comprising single-crystalline domains. Continuous rotation electron diffraction resolved the unit cell and crystal structure of both COFs, which are single-crystalline in the a–b plane but disordered in the stacking c dimension. Single crystals of both COFs were incorporated into gas chromatography separation columns and exhibited unusual selective retention of cyclohexane over benzene, with single-crystalline TAPPy-PDA significantly outperforming single-crystalline TAPB-DMPDA. Polycrystalline TAPPy-PDA exhibited no separation, while polycrystalline TAPB-DMPDA exhibited poor separation and the opposite order of elution, retaining benzene more than cyclohexane, indicating the importance of improved material quality for COFs to exhibit properties that derive from their precise, crystalline structures. This work represents the first example of synthesizing imine-linked 2D COF single crystals at ambient pressure and short reaction times and demonstrates the promise of high-quality COFs for molecular separations.

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Section: ■ Results and Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Single-Crystalline Imine-Linked Two-Dimensional Covalent Organic Frameworks Separate Benzene and Cyclohexane Efficiently

et al. 2022

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“…The solvothermal reaction takes place in a sealed and negative pressure environment, which is conducive to the full reversible reaction, long reaction time and sufficient crystallization time [72]. The β-ketoenamine-based COFs could be obtained with high crystallinity and relatively high porosity.…”

Section: Introductionmentioning

confidence: 99%

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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“…[19][20][21][22][23] COFs are a class of highly crystalline porous materials with predesigned pore structure, ultralarge SSA, and outstanding mechanical and chemical stability. [24] In addition to a well-defined skeleton topology and atomic periodicity, the structural tunability of COFs can be further extended to mesoscale by various strategies, [25][26][27][28][29] making COF a competitive material to build tailor-made microscopic and mesoscopic structures. For instance, our group recently proposed a reversible polycondensation-termination (RPT) strategy to prepare COF particles consisting of textured nanoflakes with a typical thickness of ≈30 nm.…”

Section: Introductionmentioning

confidence: 99%

Vertical Growth of 2D Covalent Organic Framework Nanoplatelets on a Macroporous Scaffold for High‐Performance Electrodes

et al. 2022

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Hierarchically structural engineering of electrodes is critical to achieving high energy density and high power density in electrochemical energy storage (EES). However, rational regulation of the mesoscopic structure that coordinates microscopic and macroscopic structural features simultaneously remains a significant challenge. Here, the construction of electrodes with well‐defined hierarchical pores spanning multiple length scales from 1 nm to 50 µm is reported. Vertically aligned 2D covalent organic framework (COF) nanoplatelets with a thickness around 30 nm are in situ grown on macroporous graphene aerogel scaffold by a reversible polycondensation‐termination strategy. The obtained electrode thus combines abundant accessible active sites and efficient transport expressways for both ions and electrons. When used for supercapacitors, a superior gravimetric capacitance of 289 F g−1 as well as outstanding capacitance retention at both high charge/discharge rates of 77% from 0.5 to 50 A g−1 and high mass loading of 74% from 1.2 to 10.4 mg cm−2 are achieved. Hierarchical engineering of mesostructured 2D COF units on the macroporous scaffold will bring unprecedented structural designability and performance enhancement for EES electrodes.

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Solvothermal depolymerization and recrystallization of imine-linked two-dimensional covalent organic frameworks

Abstract: Conditions for which imine-linked 2D COF polymerizations are temperature-sensitive are identified that enable a dissolution/repolymerization process akin to molecular recrystallization.

Cited by 20 publications

References 41 publications

Single-Crystalline Imine-Linked Two-Dimensional Covalent Organic Frameworks Separate Benzene and Cyclohexane Efficiently

Single-Crystalline Imine-Linked Two-Dimensional Covalent Organic Frameworks Separate Benzene and Cyclohexane Efficiently

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

Vertical Growth of 2D Covalent Organic Framework Nanoplatelets on a Macroporous Scaffold for High‐Performance Electrodes

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