Targeted synthesis of a porous borazine-linked covalent organic framework

Jackson, Karl T.; Reich, Thomas E.; El‐Kaderi, Hani M.

doi:10.1039/c2cc33583b

Cited by 204 publications

(169 citation statements)

References 30 publications

(16 reference statements)

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“…208,220,224,225 As expected, COF-102 and 221,225,226 The similarity of these values may be due in part to the fact that only the edge of each twodimensional layer is exposed for interactions with H 2 molecules, and suggests that such COFs are not ideal materials for practical H 2 storage. Although the impregnation of covalent organic frameworks with metal ions or metal particles could in principle lead to enhanced H 2 storage capacities, this area of synthetic research has not been widely explored.…”

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confidence: 94%

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An assessment of strategies for the development of solid-state adsorbents for vehicular hydrogen storage

Allendorf

Hulvey

Gennett

et al. 2018

Energy Environ. Sci.

217

187

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Nanoporous adsorbents are a diverse category of solid-state materials that hold considerable promise for vehicular hydrogen storage. Although impressive storage capacities have been demonstrated for several materials, particularly at cryogenic temperatures, materials meeting all of the targets established by the U.S. Department of Energy have yet to be identified. In this Perspective, we provide an overview of the major known and proposed strategies for hydrogen adsorbents, with the aim of guiding ongoing research as well as future new storage concepts. The discussion of each strategy includes current relevant literature, strengths and weaknesses, and outstanding challenges that preclude implementation. We consider in particular metal-organic frameworks (MOFs), including surface area/volume tailoring, open metal sites, and the binding of multiple H 2 molecules to a single metal site. Two related classes of porous framework materials, covalent organic frameworks (COFs) and porous aromatic frameworks (PAFs), are also discussed, as are graphene and graphene oxide and doped porous carbons. We additionally introduce criteria for evaluating the merits of a particular materials design strategy. Computation has become an important tool in the discovery of new storage materials, and a brief introduction to the benefits and limitations of computational predictions of H 2 physisorption is therefore presented. Finally, considerations for the synthesis and characterization of hydrogen storage adsorbents are discussed. IntroductionStorage of hydrogen with sufficient gravimetric and volumetric capacity for vehicular use remains a significant obstacle to the widespread adoption of hydrogen fuel cell electric vehicles (FCEVs). Several FCEV models are now commercially available in limited locations around the world, and in these vehicles hydrogen is stored as a gas at room temperature with a fill Table 1 along with the current performance of 700 bar systems. These values pertain to the entire storage system, which includes the mass and volume of hydrogen in addition to the tank and associated balance-ofplant (BOP) components. Notably, it is physically impossible to meet the 2025 and ultimate volumetric capacity target with pressurized gas, as the density of H 2 gas at 700 bar and room temperature is just 40 g L À1 without accounting for the BOP.The search for solid-state H 2 storage materials that can supplant compressed gas systems has been ongoing for at least two decades. The development of a viable storage material Broader contextThe widespread use of hydrogen as a clean, sustainable energy carrier has the potential to provide several significant benefits, including a reduction in oil dependency and emissions, improved energy security and grid resiliency, and substantial economic opportunities across many sectors. Hydrogen-fueled vehicles are already appearing internationally, and one of the critical enabling technologies for increasing their availability is on-board hydrogen storage. Stakeholders in developing a hydrogen in...

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confidence: 94%

“…217 This class of crystalline materials, known as covalent organic frameworks (COFs), now encompasses two-dimensional layered structures and three-dimensional frameworks with various linkages such as B-O, C-N, B-N, and B-O-Si. [217][218][219][220][221] Two-dimensional layered…”

Section: Covalent Organic Frameworkmentioning

confidence: 99%

An assessment of strategies for the development of solid-state adsorbents for vehicular hydrogen storage

Allendorf

Hulvey

Gennett

et al. 2018

Energy Environ. Sci.

217

187

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“…COF syntheses have predominantly been realized through reversible condensation reactions, including the formation of B–O bonds (boroxines, boronate esters, 16−18 and borosilicates 19 ), imines, 20,21 imides, 22,23 and others. 24−26 …”

Section: Introductionmentioning

confidence: 99%

From Highly Crystalline to Outer Surface-Functionalized Covalent Organic Frameworks—A Modulation Approach

et al. 2016

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Crystallinity and porosity are of central importance for many properties of covalent organic frameworks (COFs), including adsorption, diffusion, and electronic transport. We have developed a new method for strongly enhancing both aspects through the introduction of a modulating agent in the synthesis. This modulator competes with one of the building blocks during the solvothermal COF growth, resulting in highly crystalline frameworks with greatly increased domain sizes reaching several hundreds of nanometers. The obtained materials feature fully accessible pores with an internal surface area of over 2000 m2 g–1. Compositional analysis via NMR spectroscopy revealed that the COF-5 structure can form over a wide range of boronic acid-to-catechol ratios, thus producing frameworks with compositions ranging from highly boronic acid-deficient to networks with catechol voids. Visualization of an −SH-functionalized modulating agent via iridium staining revealed that the COF domains are terminated by the modulator. Using functionalized modulators, this synthetic approach thus also provides a new and facile method for the external surface functionalization of COF domains, providing accessible sites for post-synthetic modification reactions. We demonstrate the feasibility of this concept by covalently attaching fluorescent dyes and hydrophilic polymers to the COF surface. We anticipate that the realization of highly crystalline COFs with the option of additional surface functionality will render the modulation concept beneficial for a range of applications, including gas separations, catalysis, and optoelectronics.

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“…The hollow spherical COF (DhaTab), reported in this paper, consists of a macroporous inner cavity (pore width 0.5-2 mm) wrapped up by the mesoporous COF shell (width 20-40 nm). It is noteworthy that the application of COFs is still mostly limited to the storage of gas molecules, since most of the COFs synthesized are microporous in nature and their pores are not sizable enough to hold larger guests, such as enzymes [38][39][40] . While examples of mesoporous boronic acid-based COFs have been reported in the literature 41,42 their chemical instability prevents the usage of these materials for the storage of drugs and enzymes 43,44 .…”

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confidence: 99%

Self-templated chemically stable hollow spherical covalent organic framework

et al. 2015

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Covalent organic frameworks are a family of crystalline porous materials with promising applications. Although active research on the design and synthesis of covalent organic frameworks has been ongoing for almost a decade, the mechanisms of formation of covalent organic frameworks crystallites remain poorly understood. Here we report the synthesis of a hollow spherical covalent organic framework with mesoporous walls in a single-step template-free method. A detailed time-dependent study of hollow sphere formation reveals that an inside-out Ostwald ripening process is responsible for the hollow sphere formation. The synthesized covalent organic framework hollow spheres are highly porous (surface area B1,500 m 2 g À 1 ), crystalline and chemically stable, due to the presence of strong intramolecular hydrogen bonding. These mesoporous hollow sphere covalent organic frameworks are used for a trypsin immobilization study, which shows an uptake of 15.5 mmol g À 1 of trypsin.

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Targeted synthesis of a porous borazine-linked covalent organic framework

Cited by 204 publications

References 30 publications

An assessment of strategies for the development of solid-state adsorbents for vehicular hydrogen storage

An assessment of strategies for the development of solid-state adsorbents for vehicular hydrogen storage

From Highly Crystalline to Outer Surface-Functionalized Covalent Organic Frameworks—A Modulation Approach

Self-templated chemically stable hollow spherical covalent organic framework

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