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We use density functional theory, newly parameterized molecular dynamics simulations, and last generation 15 N dynamic nuclear polarization surface enhanced solid-state NMR spectroscopy (DNP SENS) to understand graft-host interactions and effects imposed by the metal-organic framework (MOF) host on peptide conformations in a peptide-functionalized MOF. Focusing on two grafts typified by MIL-68-proline (-Pro) and MIL-68-glycine-proline (-Gly-Pro), we identified the most likely peptide conformations adopted in the functionalized hybrid frameworks. We found that hydrogen bond interactions between the graft and the surface hydroxyl groups of the MOF are essential in determining the peptides conformation(s). DNP SENS methodology shows unprecedented signal enhancements when applied to these peptide-functionalized MOFs. The calculated chemical shifts of selected MIL-68-NH-Pro and MIL-68-NH-Gly-Pro conformations are in a good agreement with the experimentally obtained 15 N NMR signals. The study shows that the conformations of peptides when grafted in a MOF host are unlikely to be freely distributed, and conformational selection is directed by strong host-guest interactions., (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Summary: Monoterpenes are the most prevalent compounds found in essential oils. They exhibit inhibitory actions against phytopathogenic postharvest fungi. Direct application limits their effectiveness due to their instability, high volatility, hydrophobicity and susceptibility to degradation. Encapsulation systems using metal–organic frameworks (MOFs) have been developed to maximise their use. In this study, four protocols were shown to encapsulate thymol and limonene in porous solids, such as ZIF‐8, UiO‐66‐(COOH)2 and zeolite 13X. Vapourisation and diffusion at 60 °C for 16 h was found to be the most efficient encapsulation process. A larger amount of thymol than limonene was loaded in the porous solids. Thymol released from MOFs slowed down the growth of Colletotrichum musae by up to 6 days at 25 °C. There was a sustained release of thymol even beyond the period of maximum fungal growth. This proof‐of‐concept study revealed the potential utility of MOFs as carriers of thymol against postharvest fungi. [ABSTRACT FROM AUTHOR]

Air purification of ammonia, a toxic industrial chemicals (TICs), by adsorption process on Metal-Organic Framework solids is attracting high scientific and commercial interests. While active carbon based adsorbents required high level of relative humidity for achieving proper performance ammonia capture, zeolite performance degrades in presence of humidity. For MOFs, the presence of humidity has been shown to be MOF dependent, either beneficial or detrimental. It appears that the role of humidity is of key importance and that different ammonia adsorption mechanisms co-exist depending on the material's physico-chemical features. Based on a screening of various microporous adsorbents including carbons, zeolites and MOFs, we show that in the presence of humidity, the ammonia uptake mostly follows the Henry law of ammonia solubilization in water. At the exception of Copper based MOF, the ammonia capture is mostly correlated with the amount of “condensed water” in the micropore. We also generally observe a systematic higher uptake than the Henry law which can be attributed to the effect of confinement i. e surface-condensed phase interaction. [ABSTRACT FROM AUTHOR]

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-NH2 and Zr-fumarate. By tuning the concentration of acetic acid in water, we were able to produce, by a scalable process, UiO-66-NH2 and Zr-fumarate beads with SBET and water-sorption values comparable to the literature values obtained with other methods. [ABSTRACT FROM AUTHOR]

We use density functional theory, newly parameterized molecular dynamics simulations, and last generation 15N dynamic nuclear polarization surface enhanced solid-state NMR spectroscopy (DNP SENS) to understand graft-host interactions and effects imposed by the metal-organic framework (MOF) host on peptide conformations in a peptide-functionalized MOF. Focusing on two grafts typified by MIL-68-proline ( -Pro) and MIL-68-glycine-proline ( -Gly-Pro), we identified the most likely peptide conformations adopted in the functionalized hybrid frameworks. We found that hydrogen bond interactions between the graft and the surface hydroxyl groups of the MOF are essential in determining the peptides conformation(s). DNP SENS methodology shows unprecedented signal enhancements when applied to these peptide-functionalized MOFs. The calculated chemical shifts of selected MIL-68-NH- Pro and MIL-68-NH- Gly-Pro conformations are in a good agreement with the experimentally obtained 15N NMR signals. The study shows that the conformations of peptides when grafted in a MOF host are unlikely to be freely distributed, and conformational selection is directed by strong host-guest interactions. [ABSTRACT FROM AUTHOR]

Abstract: Metal–organic frameworks are appealing hybrid solids which attract continuously growing interest. Their advantageous application in sensing devices is demonstrated here. In particular, the use of a short‐pulse laser excitation of luminescent metal‐organic framework is reported for the first time to favor the ligand‐based emission. The designed MOF‐based system achieves in vitro H2S dosing by turn‐on fluorescence with unprecedented sensitivity. The Al‐MIL‐101‐based sensor detects sulfide produced by living cells and sulfide‐releasing molecules in physiological media with a constant accuracy at sub‐micromolar levels. The reported sensitivity is suitable for medical applications and opens new perspectives in the design of new point‐of‐care testing devices. The detailed relationship between photoluminescence mechanisms and chemical modification of the MOF upon sensing is also reported. [ABSTRACT FROM AUTHOR]

We report the supercell crystal structure of a ZIF-8 analog substituted imidazolate metal-organic framework (SIM-1) obtained by combining solid-state nuclear magnetic resonance and powder X-ray diffraction experiments with density functional theory calculations. [ABSTRACT FROM AUTHOR]

The first photosensitization of a rhodium-based catalytic system for CO2 reduction is reported, with formate as the sole carbon-containing product. Formate has wide industrial applications and is seen as valuable within fuel cell technologies as well as an interesting H2-storage compound. Heterogenization of molecular rhodium catalysts is accomplished via the synthesis, post-synthetic linker exchange, and characterization of a new metal-organic framework (MOF) Cp*Rh@UiO-67. While the catalytic activities of the homogeneous and heterogeneous systems are found to be comparable, the MOF-based system is more stable and selective. Furthermore it can be recycled without loss of activity. For formate production, an optimal catalyst loading of ~10% molar Rh incorporation is determined. Increased incorporation of rhodium catalyst favors thermal decomposition of formate into H2. There is no precedent for a MOF catalyzing the latter reaction so far. [ABSTRACT FROM AUTHOR]

Recently, the use of mixtures of organic-building-block linkers has given chemists an additional degree of freedom for engineering metal-organic frameworks (MOFs) with specific properties; however, the poor characterization of the chemical complexity of such MixMOF structures by conventional techniques hinders the verification of rational design. Herein, we describe the application of a technique known as photothermal induced resonance to individual MixMOF microcrystals to elucidate their chemical composition with nanoscale resolution. Results show that MixMOFs isoreticular to In-MIL-68, obtained either directly from solution or by postsynthetic linker exchange, are homogeneous down to approximately 100 nm. Additionally, we report a novel in situ process that enables the engineering of anisotropic domains in MOF crystals with submicron linker-concentration gradients. [ABSTRACT FROM AUTHOR]

We report two new microporous mixed-metal triazolate based MOFs made from zinc and nickel salts combined with either 1,2,4-triazole or 3,5-diamino-1,2,4-triazole. Their structures, refined from X-ray powder diffraction, their CO2 adsorption and photoluminescent properties show a direct correlation with the structure of their parent organic ligand. [ABSTRACT FROM AUTHOR]

The article offers information regarding conversion of carbon dioxide into bulk chemicals at lower energy cost. It discusses the activity of amine functionalized metal-organic frameworks. It presents the use of epoxide and carbon dioxide for the catalytic synthesis of cyclic carbonates. It investigates the various reaction involved which includes adsorption of carbon dioxide, acid-base-pair catalysis and the nucleophilic attack of the activated species.

We report herein the upscaled synthesis and shaping of UiO66-COOH for NH3 air purification. The synthesis of the zirconium-based MOF was carried out in a batch reactor in an aqueous suspension with a yield of 89% and a space-time yield of 350 kg/day/m3. Neither toxic chemicals nor organic solvents were used, allowing this MOF to be employed in individual or collective air purification devices. Freeze-granulation and extrusion shaping techniques were investigated. The NH3 air purification performances of UiO66-COOH in bead, tablet and extrudate forms were compared to those of commercial carbon based materials (type K adsorbents from3M and Norit). Testing conditions were chosen to reflect current standards for ammonia concentration (600-1200 ppm) and velocity. In addition, the breakthrough measurements were carried out at three different relative humidity levels (0%, 40%, and 70%). Pellets and extrudates of UiO66-COOH outperformed commercial benchmark adsorbents in all conditions, especially in dry conditions, for which the commercial adsorbents suffered impaired ammonia uptake and shortened service life. Extrudates of UiO66-COOH also withstood attrition after intensive shaking. [ABSTRACT FROM AUTHOR]

The article offers information regarding conversion of carbon dioxide into bulk chemicals at lower energy cost. It discusses the activity of amine functionalized metal-organic frameworks. It presents the use of epoxide and carbon dioxide for the catalytic synthesis of cyclic carbonates. It investigates the various reaction involved which includes adsorption of carbon dioxide, acid-base-pair catalysis and the nucleophilic attack of the activated species.

We present herein the first example of metal-organic frameworks postfunctionalized with peptides. Our microwave-assisted postsynthetic modification method yields enantiopure peptides anchored inside MOF cavities. Al-MIL-101-NH2, In-MIL-68-NH2, and Zr-UiO-66-NH2 were chosen as starting platforms. A single amino acid and various oligopeptides are grafted with yields up to 60% after a 30 min microwave-assisted coupling-deprotection sequence. This allows efficient preparation of a library of functional hybrid solids for molecular recognition applications such as sensing, separation, or asymmetric catalysis, as demonstrated here for the chiral aldol reaction. [ABSTRACT FROM AUTHOR]

Two cobalt imidazolate metal-organic frameworks were evaluated as a bactericidal material against the growth of the Gram-negative bacteria Pseudomonas putida and Escherichia coli. Under the most unfavourable conditions, within the exponential growth phase and in the culture media for both microorganisms, the growth inhibition reached over 50% for concentrations of biocidal material in the 5-10mgL−1 range. The release of metal gives excellent durability with the antibacterial effect persisting after 3months. Both cobalt-based materials can be prepared with simple, cheap and easily accessible commercial ligands, leading to a more affordable possible future application as antimicrobial materials. [ABSTRACT FROM AUTHOR]

The one-pot postfunctionalization allows anchoring a molecular nickel complex into a mesoporous metal-organic framework (Ni@(Fe)MIL-101). It is generating a very active and reusable catalyst for the liquid-phase ethylene dimerization to selectively form 1-butene. Higher selectivity for 1-butene is found using the Ni@(Fe)MIL-101 catalyst than reported for molecular nickel diimino complexes. [ABSTRACT FROM AUTHOR]

Abstract: In this work, we report a quantitative structure-activity relationship of functionalized ZIF-type materials (SIM, Substituted Imidazolate Material). Keeping the catalytic center unmodified, post-synthetic modification allows an efficient control of the hydrophilic–hydrophobic balance which drives the competitive adsorption of reactants and products. Hence, we attribute the increase in the reaction rate of Knoevenagel condensation (up to seven times) to the modification of the environment of catalytic sites through the creation of hydrophobic environment surrounding the catalytic sites. Surface tension properties are monitored by measuring the contact angle with a water droplet on a SIM thin film grown on a flat support. We show that the contact angle is directly correlated to the catalytic activity of Knoevenagel condensation. Hence, we propose that the contact angle of a catalyst thin layer with water can be a quantitative descriptor of direct relevance for catalytic processes which produces water and/or for catalysts that are poisoned with water. Finally, we measured the intrinsic reaction rate free of external and internal diffusion limitations by controlling the thickness of the SIM shell on SIM/alumina beads. Insights on the localization of the active sites (surface vs. bulk) are provided. [Copyright &y& Elsevier]

Abstract: For economic and environmental reasons, there is a strong incentive to replace of homogeneous by green and efficient heterogeneous processes in catalysis. The Friedel-Crafts alkylation of aromatics is a marking example. Numbers of homogeneous catalysts (such as HF, H2SO3, and AlCl3) have been replaced by H-form zeolites. However, large pore zeolite can not accommodate bulk aromatic molecules and/or alkylating agents avoiding the reaction to take place within the porous network. Due to their larger pore size, metal-organic frameworks (MOFs) open the doors to the alkylation of very large poly-aromatic compounds. We report different approaches for the design of acid shape selective MOFs. The first refers to a “zeolite mimetic” approach. It deals with the design of porous Zn or Al based MOF exhibiting bridging –OH species (MOF-69, MIL-53 Al) like those found in zeolites [Si–O(H)–Al]. The second approach aims at synthesizing MOF materials having structural defects to generate active catalytic centers. Two different synthetic strategies were investigated, either by fast precipitation or by the partial substitution of dicarboxylic by mono-carboxylic acid linkers. Acid centers have been characterized by solid 1H NMR and Diffuse Reflectance IR. The mono-alkylation of biphenyl with tert-BuCl is achieved with 100% of para-selectivity, well superior to H-MOR and H-BEA reference zeolites. [Copyright &y& Elsevier]

Hydrogen uptake at 298 K and 30 bar in hybrid sorbents consisting of n-hexane confined in MIL-101 is found to be 22 times larger than in sole n-hexane. The enhanced solubility in MIL-101, found to be 3 times larger than in mesoporous silica of similar pore size, highlights the key roles played by surface chemistry and accessible surface area. [ABSTRACT FROM AUTHOR]