25 Years of Reticular Chemistry Freund, Ralph; Canossa, Stefano; Cohen, Seth M. ...
Angewandte Chemie International Edition,
November 2, 2021, Letnik:
60, Številka:
45
Journal Article
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At its core, reticular chemistry has translated the precision and expertise of organic and inorganic synthesis to the solid state. While initial excitement over metal–organic frameworks (MOFs) and ...covalent organic frameworks (COFs) was undoubtedly fueled by their unprecedented porosity and surface areas, the most profound scientific innovation of the field has been the elaboration of design strategies for the synthesis of extended crystalline solids through strong directional bonds. In this contribution we highlight the different classes of reticular materials that have been developed, how these frameworks can be functionalized, and how complexity can be introduced into their backbones. Finally, we show how the structural control over these materials is being extended from the molecular scale to their crystal morphology and shape on the nanoscale, all the way to their shaping on the bulk scale.
Reticular chemistry translates the precision and expertise of organic and inorganic synthesis to the solid state. The most profound innovation of the field has been the elaboration of design strategies for the synthesis of extended crystalline solids through strong directional bonds. This Review highlights the classes of reticular materials, their functionalization, and the introduction of complexity into their backbones.
To gain insight into chiral recognition in porous materials we have prepared a family of fourth generation chiral metal–organic frameworks (MOFs) that have rigid frameworks and adaptable (flexible) ...pores. The previously reported parent material, Co2(S‐mandelate)2(4,4′‐bipyridine)3(NO3)2, CMOM‐1S, is a modular MOF; five new variants in which counterions (BF4−, CMOM‐2S) or mandelate ligands are substituted (2‐Cl, CMOM‐11R; 3‐Cl, CMOM‐21R; 4‐Cl, CMOM‐31R; 4‐CH3, CMOM‐41R) and the existing CF3SO3− variant CMOM‐3S are studied herein. Fine‐tuning of pore size, shape, and chemistry afforded a series of distinct host–guest binding sites with variable chiral separation properties with respect to three structural isomers of phenylpropanol. Structural analysis of the resulting crystalline sponge phases revealed that host–guest interactions, guest–guest interactions, and pore adaptability collectively determine chiral discrimination.
The chiral recognition mechanism of a family of chiral metal–organic materials was investigated towards the resolution of three racemic mixtures of phenylpropanol. X‐ray single‐crystal analysis of host–guest interactions revealed the specific binding sites with shape complementarity between the guest molecules and the adaptable chiral cavity.
A new type of composite material involving the in situ immobilization of tin oxide nanoparticles (SnO2‐NPs) within a monolithic metal–organic framework (MOF), the zeolitic imidazolate framework ...(ZIF)‐8 is presented. SnO2@monoZIF‐8 exploits the mechanical properties, structural resilience, and high density of a monolithic MOF, while leveraging the photocatalytic action of the nanoparticles. The composite displays outstanding photocatalytic properties and represents a critical advance in the field of treating toxic effluents and is a vital validation for commercial application. Crucially, full retention of catalytic activity is observed after ten catalytic cycles.
A new type of composite material involving the in situ immobilization of photoactive tin oxide nanoparticles within a monolithic metal–organic framework, monoZIF‐8, is presented. SnO2@monoZIF‐8 displays outstanding photocatalytic properties with full retention of activity observed after ten catalytic cycles. This achievement represents a critical advance in the field of treating toxic effluents and is a vital validation for commercial applications.
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.
Among a plethora of nano‐sized therapeutics, metal‐organic frameworks (MOFs) have been some of the most investigated novel materials for, predominantly, cancer drug delivery applications. Due to ...their large drug uptake capacities and slow‐release mechanisms, MOFs are desirable drug delivery vehicles that protect and transport sensitive drug molecules to target sites. The inclusion of other guest materials into MOFs to make MOF‐composite materials has added further functionality, from externally triggered drug release to improved pharmacokinetics and diagnostic aids. MOF‐composites are synthetically versatile and can include examples such as magnetic nanoparticles in MOFs for MRI image contrast and polymer coatings that improve the blood‐circulation time. From synthesis to applications, this review will consider the main developments in MOF‐composite chemistry for biomedical applications and demonstrate the potential of these novel agents in nanomedicine. It is concluded that, although vast synthetic progress has been made in the field, it requires now to develop more biomedical expertise with a focus on rational model selection, a major comparative toxicity study, and advanced targeting techniques.
Metal–organic frameworks (MOFs) are polymeric coordination networks that have recently proposed for drug‐delivery applications. The inclusion of guest materials into MOFs to make MOF‐composites adds further functionality to both diagnostics and therapeutic action. From synthesis to applications, this review considers the main developments in MOF‐composite chemistry and its contribution to the next generation of theragnostic nanomedicine.
The metal–organic frameworks (MOFs) M(BPZNO2) (M=Co, Cu, Zn; H2BPZNO2=3‐nitro‐4,4′‐bipyrazole) were prepared through solvothermal routes and were fully investigated in the solid state. They showed ...good thermal stability both under a N2 atmosphere and in air, with decomposition temperatures peaking up to 663 K for Zn(BPZNO2). Their crystal structure is characterized by 3D networks with square (M=Co, Zn) or rhombic (M=Cu) channels decorated by polar NO2 groups. As revealed by N2 adsorption at 77 K, they are micro‐mesoporous materials with BET specific surface areas ranging from 400 to 900 m2 g−1. Remarkably, under the mild conditions of 298 K and 1.2 bar, Zn(BPZNO2) adsorbs 21.8 wt % CO2 (4.95 mmol g−1). It shows a Henry CO2/N2 selectivity of 15 and an ideal adsorbed solution theory (IAST) selectivity of 12 at p=1 bar. As a CO2 adsorbent, this compound is the best‐performing MOF to date among those bearing a nitro group as a unique chemical tag. High‐resolution powder X‐ray diffraction at 298 K and different CO2 loadings revealed, for the first time in a NO2‐functionalized MOF, the insurgence of primary host–guest interactions involving the C(3)–NO2 moiety of the framework and the oxygen atoms of carbon dioxide, as confirmed by Grand Canonical Monte Carlo simulations. This interaction mode is markedly different from that observed in NH2‐functionalized MOFs, for which the carbon atom of CO2 is involved.
Catching on: As CO2‐capture materials, NO2‐functionalized bis(pyrazolate) metal–organic frameworks (MOFs) adsorb 21.8 wt % CO2 under ambient conditions. A preferential O(CO2)–C‐NO2 interaction is confirmed by experiment and theory. These compounds are the best‐performing MOFs to date among those bearing a nitro group as a unique chemical tag.
Hydrogen storage by cryoadsorption on porous materials has the advantages of low material cost, safety, fast kinetics, and high cyclic stability. The further development of this technology requires ...reliable data on the H2 uptake of the adsorbents, however, even for activated carbons the values between different laboratories show sometimes large discrepancies. So far no reference material for hydrogen cryoadsorption is available. The metal‐organic framework ZIF‐8 is an ideal material possessing high thermal, chemical, and mechanical stability that reduces degradation during handling and activation. Here, we distributed ZIF‐8 pellets synthesized by extrusion to 9 laboratories equipped with 15 different experimental setups including gravimetric and volumetric analyzers. The gravimetric H2 uptake of the pellets was measured at 77 K and up to 100 bar showing a high reproducibility between the different laboratories, with a small relative standard deviation of 3–4 % between pressures of 10–100 bar. The effect of operating variables like the amount of sample or analysis temperature was evaluated, remarking the calibration of devices and other correction procedures as the most significant deviation sources. Overall, the reproducible hydrogen cryoadsorption measurements indicate the robustness of the ZIF‐8 pellets, which we want to propose as a reference material.
Assuring the reliability of hydrogen cryoadsorption measurements requires a robust reference material. Here we distributed a commercially produced metal‐organic framework ZIF‐8 in the form of pellets for an interlaboratory study on hydrogen adsorption isotherms at 77 K. The results show a low standard deviation and prove the material batch′s high homogeneity, therefore, making ZIF‐8 pellets a promising candidate for a reference material.
We report the generation and characterization of the most complete collection of metal–organic frameworks (MOFs) maintained and updated, for the first time, by the Cambridge Crystallographic Data ...Centre (CCDC). To set up this subset, we asked the question “what is a MOF?” and implemented a number of “look-for-MOF” criteria embedded within a bespoke Cambridge Structural Database (CSD) Python API workflow to identify and extract information on 69 666 MOF materials. The CSD MOF subset is updated regularly with subsequent MOF additions to the CSD, bringing a unique record for all researchers working in the area of porous materials around the world, whether to perform high-throughput computational screening for materials discovery or to have a global view over the existing structures in a single resource. Using this resource, we then developed and used an array of computational tools to remove residual solvent molecules from the framework pores of all the MOFs identified and went on to analyze geometrical and physical properties of nondisordered structures.
Hungry hungry micropores: Reaction of Zn4(μ3‐OH)2(L)4(tBu)2 (LH=8‐hydroxyquinoline) with CO2 forms a 3D microporous material with spherical zinc carbonate nanoclusters packed in a diamondoid manner ...in the solid state. This compound exhibits one of the highest Brunauer—Emmett—Teller surface areas for a noncovalent porous material, with high H2, CO2, and CH4 uptake.
The environmental benefits of cleaner, gaseous fuels such as natural gas and hydrogen are widely reported. Yet, practical usage of these fuels is inhibited by current gas storage technology. Here, we ...discuss the wide-ranging potential of gas-fuels to revolutionize the energy sector and introduce the limitations of current storage technology that prevent this transition from taking place. The practical capabilities of adsorptive gas storage using porous, crystalline metal–organic frameworks (MOFs) are examined with regard to recent benchmark results and ultimate storage targets in this field. In particular, the industrial limitations of typically powdered MOFs are discussed while recent breakthroughs in MOF processing are highlighted. We offer our perspective on the future of practical, rather than purely academic, MOF developments in the increasingly critical field of environmental fuel storage.
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