2D covalent organic frameworks (COFs) are a class of porous polymers with crystalline structures. This tutorial review discusses how the concepts of supramolecular chemistry are used to add form and function to COFs through their non-covalent bonds.
We report the synthesis and characterization of a new class of 2D-covalent organic frameworks, called COFamides, whose layers are held together by amide hydrogen bonds. To accomplish this, we have designed monomers with a non-planar structure that arises from steric crowding, forcing the amide side groups out of plane with the COF sheets orienting the hydrogen bonds between the layers. The presence of these hydrogen bonds provides significant structural stabilization as demonstrated by comparison to control structures that lack hydrogen bonding capability, resulting in lower surface area and crystallinity. We have characterized both azine and imine-linked versions of these COFs, named COFamide-1 and-2, respectively, for their surface areas, pore sizes and crystallinity. In addition to these more conventional characterization methods, we also used variable temperature infrared spectroscopy (VT-IR) methods and van der Waals density functional calculations to directly observe the presence of hydrogen bonding.
Dynamic covalent bonds impart new properties to 3D printable materials that help to establish 3D printing as an accessible and efficient manufacturing technique. Here, we studied the effect of a thermally reversible Diels-Alder crosslinker on the shape stability of photoprintable resins and their self-healing properties. Resins containing different concentrations of dynamic covalent crosslinks in a polyacrylate network showed that the content of dynamic crosslinks plays a key role in balancing shape stability with self-healing ability. The shape stability of the printed objects was evaluated by measuring the dimensional changes after thermal treatment. The selfhealing efficiency of the 3D printed resins was characterized with a scratch test and tensile testing. A dynamic covalent crosslink concentration of 1.8 mol % was enough to provide 99% self-healing efficiency without disrupting the shape stability of the printed objects. Our work shows the potential of dynamic covalent bonds in broadening the availability of 3D printable materials that are compatible with vat photopolymerization.
Artificial native-like lipid bilayer systems constructed from phospholipids assembling into unilamellar liposomes allow the reconstitution of detergent-solubilized transmembrane proteins into supramolecular lipid-protein assemblies called proteoliposomes, which mimic cellular membranes. Stabilization of these complexes remains challenging because of their chemical composition, the hydrophobicity and structural instability of membrane proteins, and the lability of interactions between protein, detergent, and lipids within micelles and lipid bilayers. In this work we demonstrate that metastable lipid, protein-detergent, and protein-lipid supramolecular complexes can be successfully generated and immobilized within zeolitic-imidazole framework (ZIF) to enhance their stability against chemical and physical stressors. Upon immobilization in ZIF bio-composites, blank liposomes, and model transmembrane metal transporters in detergent micelles or embedded in proteoliposomes resist elevated temperatures, exposure to chemical denaturants, aging, and mechanical stresses. Extensive morphological and functional characterization of the assemblies upon exfoliation reveal that all these complexes encapsulated within the framework maintain their native morphology, structure, and activity, which is otherwise lost rapidly without immobilization.
Hierarchical porous
carbons (HPCs) hold great promise in energy-related applications owing
to their excellent chemical stability and well-developed porous structures.
Attention has been drawn toward developing new synthetic strategies
and precursor materials that permit greater control over composition,
size, morphology, and pore structure. There is a growing trend of
employing metal–organic frameworks (MOFs) as HPC precursors
as their highly customizable characteristics favor new HPC syntheses.
In this article, we report a biomimetically grown bacterial-templated
MOF synthesis where the bacteria not only facilitate the formation
of MOF nanocrystals but also provide morphology and porosity control.
The resultant HPCs show improved electrochemical capacity behavior
compared to pristine MOF-derived HPCs. Considering the broad availability
of bacteria and ease of their production, in addition to significantly
improved MOF growth efficiency on bacterial templates, we believe
that the bacterial-templated MOF is a promising strategy to produce
a new generation of HPCs.
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