Herein, we describe a new class of porous composites comprising metal–organic framework (MOF) crystals confined in single spherical matrices made of packed covalent‐organic framework (COF) ...nanocrystals. These MOF@COF composites are synthesized through a two‐step method of spray‐drying and subsequent amorphous (imine‐based polymer)‐to‐crystalline (imine‐based COF) transformation. This transformation around the MOF crystals generates micro‐ and mesopores at the MOF/COF interface that provide far superior porosity compared to that of the constituent MOF and COF components added together. We report that water sorption in these new pores occurs within the same pressure window as in the COF pores. Our new MOF@COF composites, with their additional pores at the MOF/COF interface, should have implications for the development of new composites.
Open pore remedy: A new class of porous composites comprising metal–organic framework (MOF) crystals confined in single spherical matrices made of packed covalent‐organic framework (COF) nanocrystals is described. These MOF@COF composites show the formation of micro‐ and mesopores at the MOF/COF interface that provide superior porosity compared to that of the constituent MOF and COF components added together.
Herein, we exploit the well‐known swelling behaviour of metal–organic frameworks (MOFs) to create a self‐folding polymer film. Namely, we show that incorporating crystals of the flexible MOF MIL‐88A ...into a polyvinylidene difluoride (PVDF) matrix affords a polymer composite film that undergoes reversible shape transformations upon exposure to polar solvents and vapours. Since the self‐folding properties of this film correlate directly with the swelling properties of the MIL‐88A crystals, it selectively bends to certain solvents and its degree of folding can be controlled by controlling the relative humidity. Moreover, it shows a shape‐memory effect at relative humidity values from 60 % to 90 %. As proof of concept, we demonstrate that these composite films can lift cargo and can be used to assemble 3D structures from 2D patterns. Our strategy is a straightforward method for designing autonomous soft materials with folding properties that can be tuned by judicious choice of the constituent flexible MOF.
MOF‐n‐Fold: The swelling behaviour of the metal–organic framework MIL‐88A is used to impart self‐folding properties to a polymer film upon exposure to polar solvents and vapours. The degree of folding of the resulting film can be controlled by changing the relative humidity, showing a shape memory effect.
Here, we report the design, synthesis, and functional testing of enzyme-powered porous micromotors built from a metal–organic framework (MOF). We began by subjecting a presynthesized microporous ...UiO-type MOF to ozonolysis, to confer it with mesopores sufficiently large to adsorb and host the enzyme catalase (size: 6–10 nm). We then encapsulated catalase inside the mesopores, observing that they are hosted in those mesopores located at the subsurface of the MOF crystals. In the presence of H2O2 fuel, MOF motors (or MOFtors) exhibit jet-like propulsion enabled by enzymatic generation of oxygen bubbles. Moreover, thanks to their hierarchical pore system, the MOFtors retain sufficient free space for adsorption of additional targeted species, which we validated by testing a MOFtor for removal of rhodamine B during self-propulsion.
Porous metal–organic frameworks (MOFs) are attracting great attention from industry, thanks to their myriad potential applications in areas such as catalysis and gas storage. Zr-MOFs (also known as ...UiO-type MOFs) are especially promising, owing to their large surface areas, high chemical versatility and remarkable hydrothermal, chemical and thermal stabilities. However, among the challenges currently precluding the industrial exploitation of MOFs is the lack of green methods for their synthesis. Herein we describe a continuous-flow spray-drying method for the simultaneous synthesis and shaping of spherical MOF microbeads in a mixture of water and acetic acid. We used this approach to build two archetypical Zr-MOFs: UiO-66-NH
2
and Zr-fumarate. By tuning the concentration of acetic acid in water, we were able to produce, by a scalable process, UiO-66-NH
2
and Zr-fumarate beads with
S
BET
and water-sorption values comparable to the literature values obtained with other methods.
Space cooling and heating, ventilation, and air conditioning (HVAC) accounts for roughly 10% of global electricity use and are responsible for ca. 1.13 gigatonnes of CO2 emissions annually. ...Adsorbent‐based HVAC technologies have long been touted as an energy‐efficient alternative to traditional refrigeration systems. However, thus far, no suitable adsorbents have been developed which overcome the drawbacks associated with traditional sorbent materials such as silica gels and zeolites. Metal–organic frameworks (MOFs) offer order‐of‐magnitude improvements in water adsorption and regeneration energy requirements. However, the deployment of MOFs in HVAC applications has been hampered by issues related to MOF powder processing. Herein, three high‐density, shaped, monolithic MOFs (UiO‐66, UiO‐66‐NH2, and Zr‐fumarate) with exceptional volumetric gas/vapor uptake are developed—solving previous issues in MOF‐HVAC deployment. The monolithic structures across the mesoporous range are visualized using small‐angle X‐ray scattering and lattice‐gas models, giving accurate predictions of adsorption characteristics of the monolithic materials. It is also demonstrated that a fragile MOF such as Zr‐fumarate can be synthesized in monolithic form with a bulk density of 0.76 gcm−3 without losing any adsorption performance, having a coefficient of performance (COP) of 0.71 with a low regeneration temperature (≤ 100 °C).
Monolithic zirconium‐based metal‐organic frameworks (UiO‐66, UiO‐66‐NH2 and Zr‐fumarate) with high density and exceptional water sorption capacity are developed to replace traditional refrigeration systems with energy‐efficient alternatives. The adsorption characteristics of monolithic materials have been predicted using small‐angle X‐ray scattering and lattice‐gas models. Unlike traditional MOFs, these monolithic MOFs have overcome processing issues, making them suitable for real‐world applications.
Here, a two‐step method is reported that enables imparting new functionalities to covalent organic frameworks (COFs) by nanoparticle confinement. The direct reaction between ...1,3,5‐tris(4‐aminophenyl)benzene and 1,3,5‐benzenetricarbaldehyde in the presence of a variety of metallic/metal‐oxide nanoparticles resulted in embedding of the nanoparticles in amorphous and non‐porous imine‐linked polymer organic spheres (NP@a‐1). Post‐treatment reactions of NP@a‐1 with acetic acid under reflux led to crystalline and porous imine‐based COF‐hybrid spheres (NP@c‐1). Interestingly, Au@c‐1 and Pd@c‐1 were found to be catalytically active.
Keeping nanoparticles in their place: A simple two‐step method allows encapsulating several functional nanoparticles into porous and crystalline imine‐based covalent organic framework (COF) spheres. The embedded nanoparticles are accessible to external species, thereby expanding the scope of these COF–nanoparticle hybrids to applications such as catalysis.
Materials with surfaces that can be switched from high/superhydrophobicity to superhydrophilicity are useful for myriad applications. Herein, we report a metal–organic framework (MOF) assembled from ...ZnII ions, 1,4‐benzenedicarboxylate, and a hydrophobic carborane‐based linker. The MOF crystal‐surface can be switched between hydrophobic and superhydrophilic through a chemical treatment to remove some of the building blocks.
Switching surfaces: A metal–organic framework, based on 2D layers of Zn4(bdc)2 connected through a pillaring hydrophobic carborane‐based linker, switches from hydrophobic to superhydrophilic and vice versa, upon chemical treatment.
New functional TiO2-clay nanoarchitectures based on layered and fibrous silicates and incorporating Pd and Pt noble metal nanoparticles (NPs) have been synthesized by applying a sol–gel methodology ...that involves the use of commercial organoclays. The incorporation of the noble metal NPs can be done using two different approaches: i) direct addition to the synthesis medium of a noble metal precursor (typically acetylacetonate) during the generation of the nanoarchitecture, and ii) selective photodeposition of the noble metal NPs in a post-treatment of the TiO2-clay nanoarchitecture. The resulting materials have been characterized by means of XRD, FTIR, Raman, 29Si-NMR, FE-SEM, TEM and N2 adsorption–desorption isotherms. The efficiency of these nanoarchitectures in the photocatalytic hydrogen production has been tested in the photoreforming of methanol. The higher rate in the hydrogen production corresponds to the nanoarchitectures containing Pt and TiO2 NPs derived from sepiolite.
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•New functional porous clay-nanoarchitectures containing TiO2 nanoparticles from organoclays with photoactivity were obtained by sol-gel method.•Incorporation of Pd or Pt to the TiO2-nanoarchitecture is done: i) by in situ generation during its synthesis, or ii) by noble metal photodeposition.•Pt- and Pd-TiO2-clay nanoarchitectures show high efficiency in the photoreforming of methanol for hydrogen production.•The TiO2-sepiolite nanoarchitecture with photodeposited Pt shows H2 production up to 7 fold to that of Pt-TiO2 catalyst.
Self-assembly of particles into long-range, three-dimensional, ordered superstructures is crucial for the design of a variety of materials, including plasmonic sensing materials, energy or gas ...storage systems, catalysts and photonic crystals. Here, we have combined experimental and simulation data to show that truncated rhombic dodecahedral particles of the metal-organic framework (MOF) ZIF-8 can self-assemble into millimetre-sized superstructures with an underlying three-dimensional rhombohedral lattice that behave as photonic crystals. Those superstructures feature a photonic bandgap that can be tuned by controlling the size of the ZIF-8 particles and is also responsive to the adsorption of guest substances in the micropores of the ZIF-8 particles. In addition, superstructures with different lattices can also be assembled by tuning the truncation of ZIF-8 particles, or by using octahedral UiO-66 MOF particles instead. These well-ordered, sub-micrometre-sized superstructures might ultimately facilitate the design of three-dimensional photonic materials for applications in sensing.
This work reports on the synthesis of nanosheets of layered titanosilicate JDF-L1 supported on commercial E-type glass fibers with the aim of developing novel nanoarchitectures useful as robust and ...easy to handle hydrogen adsorbents. The preparation of those materials is carried out by hydrothermal reaction from the corresponding gel precursor in the presence of the glass support. Because of the basic character of the synthesis media, silica from the silicate-based glass fibers can be involved in the reaction, cementing its associated titanosilicate and giving rise to strong linkages on the support with the result of very stable heterostructures. The nanoarchitectures built up by this approach promote the growth and disposition of the titanosilicate nanosheets as a house-of-cards radially distributed around the fiber axis. Such an open arrangement represents suitable geometry for potential uses in adsorption and catalytic applications where the active surface has to be available. The content of the titanosilicate crystalline phase in the system represents about 12 wt %, and this percentage of the adsorbent fraction can achieve, at 298 K and 20 MPa, 0.14 wt % hydrogen adsorption with respect to the total mass of the system. Following postsynthesis treatments, small amounts of Pd (<0.1 wt %) have been incorporated into the resulting nanoarchitectures in order to improve their hydrogen adsorption capacity. In this way, Pd-layered titanosilicate supported on glass fibers has been tested as a hydrogen adsorbent at diverse pressures and temperatures, giving rise to values around 0.46 wt % at 298 K and 20 MPa. A mechanism of hydrogen spillover involving the titanosilicate framework and the Pd nanoparticules has been proposed to explain the high increase in the hydrogen uptake capacity after the incorporation of Pd into the nanoarchitecture.
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