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Crystalline Covalent Organic Frameworks from Triazine Nodes as Porous Adsorbents for Dye Pollutants.

ABSTRACT: The development of covalent organic frameworks (COFs) with nodes and spacers, designed to maximize their functional properties, is a challenge. Triazines exhibit better electron affinity than benzene-based aromatic rings; therefore, structures based on 1,3,5-substituted triazine-centered nodes are more stable than those from 1,3,5-benzene-linked COFs. Compared to COFs prepared from flat, rigid sp2 carbon-linked triazine nodes, the O-linked flexible tripodal triazine-based COF demonstrates several unpredictable properties such as an increase in crystallinity and cavity size. In this study, the COF prepared from O-linked flexible 2,4,6-tris(p-formylphenoxy)-1,3,5-triazine serves as an excellent absorbent for removing methylene blue from water. Our results demonstrate that COF is highly stable in water and functions as a robust adsorbent. Its adsorption isotherm is consistent with the Langmuir model and its adsorption kinetics follows a pseudo-second order model. Moreover, the COF was characterized using elemental analysis, Fourier transform infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy, solid-state ultraviolet-visible spectroscopy, and X-ray diffraction. It exhibited permanent porosity, a high specific surface area (279.5 m2·g-1), and was chemically and thermally stable. Photophysical studies revealed that the COF exhibits a low bandgap energy value of 3.07 eV, indicating its semiconducting nature.

SUBMITTER: Huo J

PROVIDER: S-EPMC6941375 | biostudies-literature | 2019 Dec

REPOSITORIES: biostudies-literature

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Crystalline Covalent Organic Frameworks from Triazine Nodes as Porous Adsorbents for Dye Pollutants.

Huo Jianqiang J Luo Bingcai B Chen Ying Y

ACS omega 20191218 27

The development of covalent organic frameworks (COFs) with nodes and spacers, designed to maximize their functional properties, is a challenge. Triazines exhibit better electron affinity than benzene-based aromatic rings; therefore, structures based on 1,3,5-substituted triazine-centered nodes are more stable than those from 1,3,5-benzene-linked COFs. Compared to COFs prepared from flat, rigid sp<sup>2</sup> carbon-linked triazine nodes, the O-linked flexible tripodal triazine-based COF demonstr ...[more]

PMID: 31909333

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Project description:Several synthetic methods have recently emerged to develop high-surface-area solid-state organic framework-based materials into free-flowing liquids with permanent porosity. The fluidity of these porous liquid (PL) materials provides them with advantages in certain storage and transport processes. However, most framework-based materials necessitate the use of cryogenic temperatures to store weakly bound gases such as H2, temperatures where PLs lose their fluidity. Covalent organic framework (COF)-based PLs that could reversibly form stable complexes with H2 near ambient temperatures would represent a promising development for gas storage and transport applications. We report here the development, characterization, and evaluation of a material with these remarkable characteristics based on Cu(I)-loaded COF colloids. Our synthetic strategy required tailoring conditions for growing robust coatings of poly(dimethylsiloxane)-methacrylate (PDMS-MA) around COF colloids using atom transfer radical polymerization (ATRP). We demonstrate exquisite control over the coating thickness on the colloidal COF, quantified by transmission electron microscopy and dynamic light scattering. The coated COF material was then suspended in a liquid polymer matrix to make a PL. CO2 isotherms confirmed that the coating preserved the general porosity of the COF in the free-flowing liquid, while CO sorption measurements using diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) confirmed the preservation of Cu(I) coordination sites. We then evaluated the gas sorption phenomenon in the Cu(I)-COF-based PLs using DRIFTS and temperature-programmed desorption measurements. In addition to confirming that H2 transport is possible at or near mild refrigeration temperatures with these materials, our observations indicate that H2 diffusion is significantly influenced by the glass-transition temperature of both the coating and the liquid matrix. The latter result underscores an additional potential advantage of PLs in tailoring gas diffusion and storage temperatures through the coating composition.

Dataset Information

Crystalline Covalent Organic Frameworks from Triazine Nodes as Porous Adsorbents for Dye Pollutants.

Publications

Crystalline Covalent Organic Frameworks from Triazine Nodes as Porous Adsorbents for Dye Pollutants.

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