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Endohedral Hydrogen Bonding Templates the Formation of a Highly Strained Covalent Organic Cage Compound*.

ABSTRACT: A highly strained covalent organic cage compound was synthesized from hexahydroxy tribenzotriquinacene (TBTQ) and a meta-terphenyl-based diboronic acid with an additional benzoic acid substituent in 2'-position. Usually, a 120° bite angle in the unsubstituted ditopic linker favors the formation of a [4+6] cage assembly. Here, the introduction of the benzoic acid group is shown to lead to a perfectly preorganized circular hydrogen-bonding array in the cavity of a trigonal-bipyramidal [2+3] cage, which energetically overcompensates the additional strain energy caused by the larger mismatch in bite angles for the smaller assembly. The strained cage compound was analyzed by mass spectrometry and ¹ H, ¹³ C and DOSY NMR spectroscopy. DFT calculations revealed the energetic contribution of the hydrogen-bonding template to the cage stability. Furthermore, molecular dynamics simulations on early intermediates indicate an additional kinetic effect, as hydrogen bonding also preorganizes and rigidifies small oligomers to facilitate the exclusive formation of smaller and more strained macrocycles and cages.

SUBMITTER: Schafer N

PROVIDER: S-EPMC8048910 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Isoreticular Crystallization of Highly Porous Cubic Covalent Organic Cage Compounds*.

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| S-EPMC8362030 | biostudies-literature

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| S-EPMC9168829 | biostudies-literature

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| S-EPMC7586335 | biostudies-literature

How to not build a cage: endohedral functionalization of polyoxometalate-based metal-organic polyhedra.

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| S-EPMC8171318 | biostudies-literature

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| S-EPMC6295888 | biostudies-literature

Constructing covalent organic frameworks in water <i>via</i> dynamic covalent bonding.

Project description:The formation of keto-enamine based crystalline, porous polymers in water is investigated for the first time. Facile access to the Schiff base reaction in water has been exploited to synthesize stable porous structures using the principles of Dynamic Covalent Chemistry (DCC). Most credibly, the water-based Covalent Organic Frameworks (COFs) possess chemical as well as physical properties such as crystallinity, surface area and porosity, which is comparable to their solvothermal counterparts. The formation of COFs in water is further investigated by understanding the nature of the monomers formed using hydroxy and non-hydroxy analogues of the aldehyde. This synthetic route paves a new way to synthesize COFs using a viable, greener route by utilization of the DCC principles in conjunction with the keto-enol tautomerism to synthesize useful, stable and porous COFs in water.

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Project description:A trigonal-bipyramidal covalent organic cage compound serves as an efficient host to form stable 1 : 1-complexes with C60 and C70. Fullerene encapsulation has been comprehensively studied by NMR and UV/Vis spectroscopy, mass spectrometry as well as single-crystal X-ray diffraction. Exohedral functionalization of encapsulated C60 via threefold Prato reaction revealed high selectivity for the symmetry-matched all-trans-3 addition pattern.

| S-EPMC8163405 | biostudies-literature

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| S-EPMC3950890 | biostudies-other

Highly crystalline and water-wettable benzobisthiazole-based covalent organic frameworks for enhanced photocatalytic hydrogen production

Project description:ABSTRACT Two-dimensional covalent organic frameworks are promising for photocatalysis by virtue of their structural and functional diversity, but generally suffer from low activities relative to their inorganic competitors. To fulfill their full potential requires a rational tailoring of their structures at different scales as well as their surface properties. Herein, we demonstrate benzobisthiazole-based covalent organic frameworks as a superior photocatalyst for hydrogen production. The product features high crystallinity with ordered 2.5-nm-wide cylindrical mesopores and great water wettability. These structural advantages afford our polymeric photocatalyst with fast charge carrier dynamics as evidenced by a range of spectroscopic characterizations and excellent catalytic performances when suspended in solution or supported on melamine foams. Under visible-light irradiation, it enables efficient and stable hydrogen evolution with a production rate of 487 μmol h−1 (or a mass-specific rate of 48.7 mmol g−1 h−1)—far superior to the previous state of the art. We also demonstrate that hydrogen production can be stoichiometrically coupled with the oxidation conversion of biomass as exemplified by the conversion of furfuryl alcohol to 2-furaldehyde. Semiconducting benzobisthiazole-based covalent organic frameworks were prepared and reported. Its high crystallinity, great water-wettability and fast charge separation dynamics cooperatively endow the material with an extraordinary H2 evolution rate of 48.7 mmol g1 h1 under visible light irradiation.

| S-EPMC9843129 | biostudies-literature

Facile synthesis of novel porous self-assembling hydrogen-bonding covalent organic polymers and their applications towards fluoroquinolone antibiotics adsorption.

Project description:A series of porous hydrogen-bonding covalent organic polymers (HCOPs) have been synthesized based on three-composite building blocks through a quick and succinct method for fluoroquinolone antibiotics adsorption from aqueous solutions. The porous properties of the HCOPs were regulated and controlled by adjusting the lengths of linkers, and the crystallinity and stability were strengthened due to the introduction of hydrogen bonds in HCOPs. Taking advantage of the porous properties and π-conjugated phenyl rings, as well as functional -CO-NH- and -COOH groups, HCOPs removed organic pollutants from wastewater effectively and showed good reusability. The external adsorption behavior was analyzed using both kinetic analysis and isotherm analysis. The results showed that the adsorption obeys the pseudo-second order kinetic model and follows the Langmuir isotherm model. The obtained maximum adsorption capacity of the four HCOPs was arranged in sequence according to the specific surface areas and pore sizes. Furthermore, the internal mechanisms involving perforated porousness, electrostatic interaction, hydrophobic interaction, π-π electron-donor-acceptor (EDA) interaction and hydrogen bonding formation, were investigated in detail. We envisage broadly applying the HCOPs in the facile and effective management of environmental pollution.

| S-EPMC9086438 | biostudies-literature

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