Abstract:A large-pore version of Mg-CUK-1, a water-stable metal−organic framework (MOF) with 1-D channels, was synthesized in basic water. Mg-CUK-1L has a BET surface area of 2896 m 2 g −1 and shows stark selectivity for CO 2 sorption over N 2 , O 2 , H 2 , and CH 4 . It displays reversible, multistep gated sorption of CO 2 below 0.33 atm. The dehydrated single-crystal structure of Mg-CUK-1L confirms retention of the open-channel structure. The MOF can be loaded with organic molecules by immersion in hot melts, providi… Show more
“…[19] By anchoring azobenzene or its derivatives within liquid-crystalline networks (LCNs), high-speed actuation on the micro-and nanoscale was successfully realized. [19] In addition to actuation, [20][21][22] artificial muscle contraction, [23] shape memory, [24] phase transition, [25] and motion in liquids, [26] azobenzenes were employed in more constrained environments, such as molecular crystals, [27,28] thin films, [29] and hydrogels. [30] As opposed to widely-reported photo-induced mechanical motion, the photo-modulation of the mechanical performance, for example, stiffness and toughness, of bulk materials remains a considerable challenge.…”
Light-responsive materials have been extensively studied due to the attractive possibility of manipulating their properties with high spatiotemporal control in a non-invasive fashion. This stimulated the development of a series of photodeformable smart devices. However, it remained a challenge to reversibly modulate the stiffness and toughness of bulk materials. Here, we present bioengineered protein fibers and their optomechanical manipulation by employing electrostatic interactions between supercharged polypeptides (SUPs) and an azobenzene (Azo)-based surfactant. Photo-isomerization of the Azo moiety from the E-to Z-form reversibly triggered the modulation of tensile strength, stiffness, and toughness of the bulk protein fiber. Specifically, the photo-induced rearrangement into the Z-form of Azo possibly strengthened cation-p interactions within the fiber material, resulting in an around twofold increase in the fibers mechanical performance. The outstanding mechanical and responsive properties open a path towards the development of SUP-Azo fibers as smart stimuli-responsive mechano-biomaterials.
“…[19] By anchoring azobenzene or its derivatives within liquid-crystalline networks (LCNs), high-speed actuation on the micro-and nanoscale was successfully realized. [19] In addition to actuation, [20][21][22] artificial muscle contraction, [23] shape memory, [24] phase transition, [25] and motion in liquids, [26] azobenzenes were employed in more constrained environments, such as molecular crystals, [27,28] thin films, [29] and hydrogels. [30] As opposed to widely-reported photo-induced mechanical motion, the photo-modulation of the mechanical performance, for example, stiffness and toughness, of bulk materials remains a considerable challenge.…”
Light-responsive materials have been extensively studied due to the attractive possibility of manipulating their properties with high spatiotemporal control in a non-invasive fashion. This stimulated the development of a series of photodeformable smart devices. However, it remained a challenge to reversibly modulate the stiffness and toughness of bulk materials. Here, we present bioengineered protein fibers and their optomechanical manipulation by employing electrostatic interactions between supercharged polypeptides (SUPs) and an azobenzene (Azo)-based surfactant. Photo-isomerization of the Azo moiety from the E-to Z-form reversibly triggered the modulation of tensile strength, stiffness, and toughness of the bulk protein fiber. Specifically, the photo-induced rearrangement into the Z-form of Azo possibly strengthened cation-p interactions within the fiber material, resulting in an around twofold increase in the fibers mechanical performance. The outstanding mechanical and responsive properties open a path towards the development of SUP-Azo fibers as smart stimuli-responsive mechano-biomaterials.
“…After each UV irradiation, the absorption can be recovered to its initial state in the dark. We expect that these compounds also display the photoisomerization properties in solid state and plan to further study their potential application in the field of optical switch and optical information storage [ 39 ]. Figure 5.…”
New azobenzene derivatives with dihydropyrazole heterocycle have been prepared and characterized. According to thermal polarizing microscopy and differential scanning calorimetry studies, the compounds consisting of four linearly linked rings and a long alkoxy chain on the azobenzene side (
3a-8
and
3a-14
) displayed no liquid crystal properties. When the length of mesogenic unit increased to five rings, except for compound
5a-8
, all compounds from
5a-10
to
5a-16
containing a long chain of 10–16 carbon atoms on the side of ester group displayed liquid crystalline properties, and the mesogenic domain gradually narrowed with increase of the chain length. However, in the case of the molecule with long alkoxy chains on both sides, only
5c-16
with a long chain of 16 carbon atoms exhibited liquid crystal behaviour. In addition, these azo compounds underwent isomerization from E to Z under ultraviolet irradiation and then thermal back relaxation slowly in the dark, which can be recycled many times.
“…Firstly, the classical azobenzene is preferentially chosen as it can be reversibly switched between trans ( E ) and cis ( Z ) isomers with good photostability by exposing lights of different wavelengths [48] . Indeed, azobenzene guests have been actively used in photo‐responsive materials such as dynamic cage and metal–organic frameworks (MOFs) [6, 49–51] . Secondly, as for the SCO host, the porous Hofmann‐type Fe II MOFs provide a promising platform, in which extraordinary SCO properties, diverse pore sizes and dynamic host–guest interactions have been well documented [52–56] .…”
Stimuli‐responsive materials that can be reversibly switched by light are of immense interest. Among them, photo‐responsive spin crossover (SCO) complexes have great promises to combine the photoactive inputs with multifaceted outputs into switchable materials and devices. However, the reversible control the spin‐state change by photochromic guests is still challenging. Herein, we report an unprecedented guest‐driven light‐induced spin change (GD‐LISC) in a Hofmann‐type metal–organic framework (MOF), [Fe(bpn){Ag(CN)2}2]⋅azobenzene. (1, bpn=1,4‐bis(4‐pyridyl)naphthalene). The reversible trans–cis photoisomerization of azobenzene guest upon UV/Vis irradiation in the solid‐state results in the remarkable magnetic changes in a wide temperature range of 10–180 K. This finding not only establishes a new switching mechanism for SCO complexes, but also paves the way toward the development of new generation of photo‐responsive magnetic materials.
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