Search

Flexible metal–organic framework (MOF) compounds can exhibit very pronounced structural changes, which may be favorable for gas storage and gas separation applications. The noble gases xenon and krypton are increasingly important for both research and applications. Therefore, separation approaches with lower energy consumption are of great interest. In the present paper, the adsorption of pure xenon and krypton as well as their mixture by the flexible gate pressure MOFs is investigated using in situ high-pressure 129Xe NMR spectroscopy and volumetric gas adsorption in combination with density-functional theory (DFT) calculations. The chosen model MOF compound DUT-8(Ni) can be synthesized as a flexible or rigid structure by tuning the crystallite size. This allows us to discriminate possible effects exerted by the framework flexibility from influences of structure and composition.

Surface terminations profoundly influence the intrinsic properties of MXenes, but existing terminations are limited to monoatomic layers or simple groups, showing disordered arrangements and inferior stability. Here we present the synthesis of MXenes with triatomic-layer borate polyanion terminations (OBO terminations) through a flux-assisted eutectic molten etching approach. During the synthesis, Lewis acidic salts act as the etching agent to obtain the MXene backbone, while borax generates BO2−species, which cap the MXene surface with an O–B–O configuration. In contrast to conventional chlorine/oxygen-terminated Nb2C with localized charge transport, OBO-terminated Nb2C features band transport described by the Drude model, exhibiting a 15-fold increase in electrical conductivity and a 10-fold improvement in charge mobility at the d.c. limit. This transition is attributed to surface ordering that effectively mitigates charge carrier backscattering and trapping. Additionally, OBO terminations provide Ti3C2MXene with substantially enriched Li+-hosting sites and thereby a large charge-storage capacity of 420 mAh g−1. Our findings illustrate the potential of intricate termination configurations in MXenes and their applications for (opto)electronics and energy storage.

Two‐dimensional conjugated covalent organic frameworks (2D c‐COFs) are emerging semiconductor materials for optoelectronic and photothermal applications. In particular, the highly tailorable, semiconducting thiophene‐based 2D c‐COFs have attracted considerable interest due to their nontrivial physicochemical properties such as photo‐activity, broad optical absorption, tunable electronic structures, and so forth. Herein, we demonstrate a novel, crystalline 2D c‐COF based on thienyl‐functionalized benzodithiophene (BDT) and biphenyl (BP) via the Schiff‐base polycondensation reaction. The resultant BDT‐BP‐COFexhibits a broad optical absorption up to ca. 600 nm and decent π‐conjugation along the 2D polymer skeleton, as revealed by the optical absorption and theoretical calculations. The favorable π‐conjugation and the abundant electron‐rich thiophene units confer excellent photo‐activity to BDT‐BP‐COFtowards the usage of solar energy. As a proof‐of‐concept application, we explore BDT‐BP‐COFin photothermal conversion, in which it shows a fast surface‐temperature increase upon light irradiation for seconds.

Two-dimensional conjugated polymers (2DCPs), composed of multiple strands of linear conjugated polymers with extended in-plane π-conjugation, are emerging crystalline semiconducting polymers for organic (opto)electronics. They are represented by two-dimensional π-conjugated covalent organic frameworks, which typically suffer from poor π-conjugation and thus low charge carrier mobilities. Here we overcome this limitation by demonstrating two semiconducting phthalocyanine-based poly(benzimidazobenzophenanthroline)-ladder-type 2DCPs (2DCP-MPc, with M = Cu or Ni), which are constructed from octaaminophthalocyaninato metal(ii) and naphthalenetetracarboxylic dianhydride by polycondensation under solvothermal conditions. The 2DCP-MPcs exhibit optical bandgaps of ~1.3 eV with highly delocalized π-electrons. Density functional theory calculations unveil strongly dispersive energy bands with small electron–hole reduced effective masses of ~0.15m0for the layer-stacked 2DCP-MPcs. Terahertz spectroscopy reveals the band transport of Drude-type free carriers in 2DCP-MPcs with exceptionally high sum mobility of electrons and holes of ~970 cm2V−1s−1at room temperature, surpassing that of the reported linear conjugated polymers and 2DCPs. This work highlights the critical role of effective conjugation in enhancing the charge transport properties of 2DCPs and the great potential of high-mobility 2DCPs for future (opto)electronics.

Recent developments in the field of covalent organic frameworks (COFs) describe the issue of processability. The precise tunability of delamination of such structures to obtain few layered nanosheets by synthetic control has been ventured in this study. Covalent anchoring of a series of linear and branched alkoxy side chains to the backbone of layered covalent organic frameworks was used to achieve this. To support the hypothesis, powder X-ray diffraction studies accompanied by computational modeling revealed that the elongation of side chains increases the interlayer distances of the COFs. This led to a successful study of the solvent-assisted exfoliation by atomic force microscopy techniques to obtain nanosheets with heights less than 2 nm, representing stacks of 4–5 layers. Dispersions of the functionalized COF nanosheets are stable for several hours. Furthermore, the surface properties are drastically changed, rendering the materials hydrophobic, with contact angles reaching up to 142° and complete blockage of the pore space toward water vapor. As a proof of concept, the sheets are processable and could be integrated into separators for lithium-ion batteries.

Dithiine linkage formation via a dynamic and self-correcting nucleophilic aromatic substitution reaction enables the de novo synthesis of a porous thianthrene-based two-dimensional covalent organic framework (COF). For the first time, this organo-sulfur moiety is integrated as a structural building block into a crystalline layered COF. The structure of the new material deviates from the typical planar interlayer π-stacking of the COF to form undulated layers caused by bending along the C–S–C bridge, without loss of aromaticity and crystallinity of the overall COF structure. Comprehensive experimental and theoretical investigations of the COF and a model compound, featuring the thianthrene moiety, suggest partial delocalization of sulfur lone pair electrons over the aromatic backbone of the COF decreasing the band gap and promoting redox activity. Postsynthetic sulfurization allows for direct covalent attachment of polysulfides to the carbon backbone of the framework to afford a molecular-designed cathode material for lithium–sulfur (Li–S) batteries with a minimized polysulfide shuttle. The fabricated coin cell delivers nearly 77% of the initial capacity even after 500 charge–discharge cycles at 500 mA/g current density. This novel sulfur linkage in COF chemistry is an ideal structural motif for designing model materials for studying advanced electrode materials for Li–S batteries on a molecular level.

Flexible metal–organic frameworks (MOFs) are promising materials in gas-related technologies. Adjusting the material to processes requires understanding of the flexibility mechanism and its influence on the adsorption properties. Herein, we present the mechanistic understanding of CO2-induced pore-opening transitions of the water-stable MOF JUK-8([Zn(oba)(pip)]n, oba2–= 4,4′-oxybis(benzenedicarboxylate), pip = 4-pyridyl-functionalized benzene-1,3-dicarbohydrazide) as well as its potential applicability in gas purification. Detailed insights into the global structural transformation and subtle local MOF–adsorbate interactions are obtained by three in situtechniques (XRD, IR, and 13CO2-NMR). These results are further supported by single-crystal X-ray diffraction (SC-XRD) analysis of the solvated and guest-free phases. High selectivity toward carbon dioxide derived from the single-gas adsorption experiments of CO2(195 and 298 K), Ar (84 K), O2(90 K),N2(77 K), and CH4(298 K) is confirmed by high-pressure coadsorption experiments of the CO2/CH4(75:25 v/v) mixture at different temperatures (288, 293, and 298 K) and in situNMR studies of the coadsorption of 13CO2/13CH4(50:50 v/v; 195 K).

The investigation of molecular interactions between silica phases and organic components is crucial for elucidating the main steps involved in the biosilica mineralization process. In this respect, the structural characterization of the organic/inorganic interface is particularly useful for a deeper understanding of the dominant mechanisms of biomineralization. In this work, we have investigated the interaction of selectively 13C- and 15N-labeled atoms of organic long-chain polyamines (LCPAs) with 29Si-labeled atoms of a silica layer at the molecular level. In particular, silica/LCPA nanocomposites were analyzed by solid-state NMR spectroscopy in combination with all-atom molecular dynamics simulations. Solid-state NMR experiments allow the determination of 29Si–15N and 29Si–13C internuclear distances, providing the parameters for direct verification of atomistic simulations. Our results elucidate the relevant molecular conformations as well as the nature of the interaction between the LCPA and a silica substrate. Specifically, distances and second moments suggest a picture compatible with (i) LCPA completely embedded in the silica phase and (ii) the charged amino groups located in close vicinity of silanol groups.

Luminescent organic materials with high photostability are essential in optoelectronics, sensor, and photocatalysis applications. However, small organic molecules are generally sensitive to UV irradiation, giving rise to chemical decompositions. In this work, we demonstrate two novel CN-substituted two-dimensional sp2-carbon-linked conjugated polymers (2D CCPs) containing a chromophore triphenylene unit. The Knoevenagel polymerization between 2,3,6,7,10,11-hexakis(4-formylphenyl)triphenylene (HFPTP) and 1,4-phenylenediacetonitrile (PDAN) or 2,2′-(biphenyl-4,4′-diyl)diacetonitrile (BDAN), provides the crystalline 2D CCP-HFPTP-PDAN (2D CCP-1) and 2D CCP-HFPTP-BDAN (2D CCP-2) with dual pore structures, respectively. 2D CCP-1 and 2D CCP-2 exhibit the photoluminescence quantum yield (PLQY) up to 24.9 and 32.3%, which are the highest values among the reported 2D conjugated polymers and π-conjugated 2D covalent organic frameworks. Furthermore, compared with the well-known emissive small molecule tetrakis(carbazol-9-yl)-4,6-dicyanobenzene (4CzIPN), both 2D CCPs show superior photostability under UV irradiation for 2 h, profiting from the twisted and rigid structures of the CN-substituted vinylene linkages. The present work will trigger the further explorations of novel organic emitters embedded in 2D CCPs with high PLQY and photostability, which can be useful for optoelectronic devices.

The origin of crystal-size-dependent adsorption behavior of flexible metal–organic frameworks is increasingly studied. In this contribution, we probe the solid–fluid interactions of DUT-49 crystals of different size by in situ129Xe NMR spectroscopy at 200 K. With decreasing size of the crystals, the average solid–fluid interactions are found to decrease reflected by a decrease in chemical shift of adsorbed xenon from 230 to 200 ppm, explaining the lack of adsorption-induced transitions for smaller crystals. However, recent studies propose that these results can also originate from the presence of lattice defects. To investigate the influence of defects on the adsorption behavior of DUT-49, we synthesized a series of samples with tailored defect concentrations and characterized them by in situ129Xe NMR. In comparison to the results obtained for crystals with different size, we find pronounced changes of the adsorption behavior and influence of the chemical shift only for very high concentrations of defects, which further emphasizes the important role of particle size phenomena.

Biosilica is a biogenic composite material produced by organisms like diatoms. Various biomolecules are tightly attached or incorporated into biosilica. Examples are special proteins termed silaffins and long-chain polyamines (LCPAs). Presumably, these biomolecules are involved in the biosilica formation process. Silaffins are highly phosphorylated zwitterions with LCPAs post-translationally attached to lysine residues. In the present work, we use distance-dependent solid-state NMR experiments, especially the 31P{29Si} Rotational Echo Double Resonance (REDOR) technique, to study the environment of phosphate moieties in biosilica and in vitro synthesized SiO2-based composites. In contrast to the heterogeneous mixtures of biomolecules found in native biosilica, the described in vitro silicification experiments make use of a single synthetic phosphopeptide and an LCPA of well-defined and uniform structure. The heteronuclear correlations measured from these silica composites provide reliable 31P–29Si dipolar second moments and information about the distribution of the phosphopeptide within the silica material. The calculated second moment indicates close contact between phosphopeptides and silica. The phosphopeptides are incorporated into the silica composite in a disperse manner. Moreover, the REDOR data acquired for diatom biosilica also imply that phosphate groups are part of the silica–organic interface in this material.

π-Conjugated two-dimensional covalent organic frameworks (2D COFs) are emerging as a novel class of electroactive materials for (opto)electronic and chemiresistive sensing applications. However, understanding the intricate interplay between chemistry, structure, and conductivity in π-conjugated 2D COFs remains elusive. Here, we report a detailed characterization for the electronic properties of two novel samples consisting of Zn– and Cu–phthalocyanine-based pyrazine-linked 2D COFs. These 2D COFs are synthesized by condensation of metal–phthalocyanine (M = Zn and Cu) and pyrene derivatives. The obtained polycrystalline-layered COFs are p-type semiconductors both with a band gap of ∼1.2 eV. A record device-relevant mobility up to ∼5 cm2/(V s) is resolved in the dc limit, which represents a lower threshold induced by charge carrier localization at crystalline grain boundaries. Hall effect measurements (dc limit) and terahertz (THz) spectroscopy (ac limit) in combination with density functional theory (DFT) calculations demonstrate that varying metal center from Cu to Zn in the phthalocyanine moiety has a negligible effect in the conductivity (∼5 × 10–7S/cm), charge carrier density (∼1012cm–3), charge carrier scattering rate (∼3 × 1013s–1), and effective mass (∼2.3m0) of majority carriers (holes). Notably, charge carrier transport is found to be anisotropic, with hole mobilities being practically null in-plane and finite out-of-plane for these 2D COFs.

Flexible metal–organic frameworks (MOFs) are capable of changing their crystal structure as a function of external stimuli such as pressure, temperature, and type of adsorbed guest species. DUT-49 is the first MOF exhibiting structural transitions accompanied by the counterintuitive phenomenon of negative gas adsorption. Here, we present high-pressure in situ 129Xe NMR spectroscopic studies of a novel isoreticular MOF family based on DUT-49. These porous materials differ only in the length of their organic linkers causing changes in pore size and elasticity. The series encompasses both, purely microporous materials as well as materials with both micropores and small mesopores. The chemical shift of the adsorbed xenon depends on xenon–wall interactions and thus on the pore size of the material. The xenon adsorption behavior of different MOFs can be observed over the whole range of relative pressure. Chemical shift adsorption/desorption isotherms closely resembling the conventional, uptake-measurement-based isotherms were obtained at 237 K where all materials are rigid. The comparable chemical environment of the adsorbed xenon in these isoreticular MOFs allows to establish a correlation between the chemical shift at a relative pressure of p/p0= 1.0 and the mean pore diameter. Furthermore, the xenon adsorption behavior of MOFs is studied also at 200 K. Here, structural flexibility is found for DUT-50, a material with an even longer linker than that of the previously known DUT-49. Its structural transitions are monitored by 129Xe NMR spectroscopy. This compound is the second known MOF showing the phenomenon of negative gas adsorption. Further increase in the linker length results in DUT-151, a material with an interpenetrated network topology. In situ 129Xe NMR spectroscopy proves that this material exhibits another type of flexibility compared to DUT-49 and DUT-50. Further surprising observations are made for DUT-46. Volumetric xenon adsorption measurements show that this nonflexible microporous material does not exhibit any hysteresis. In contrast, the in situ 129Xe NMR spectroscopically detected xenon chemical shift isotherms exhibit a hysteresis even after longer equilibration times than in the volumetric experiments. This indicates kinetically hindered redistribution processes and long-lived metastable states of adsorbed xenon within the MOF persisting at the time scale of hours or longer.

Immobilizing enzymes on solid support materials is of great interest for many applications as it improves enzyme lifetime and enables its recycling. Synthetic mesoporous silica materials are widely used as supports for enzyme immobilization due to their high enzyme-loading capacity and their excellent mass transport properties through interconnected channels of mesopores. Much less is known about the enzyme support properties of naturally occurring mesoporous silica materials. These are readily available through the growth of diatoms, which biosynthesize hierarchically porous silica microshells with pore diameters ranging from 10 to 1000 nm. Here the authors investigated the performance as enzyme support materials of biosilica from three diatom species in comparison to synthetic silica materials. Using glucose oxidase (GOx) as a model enzyme, the authors determined the enzyme-loading capacities and the specific catalytic activities of the GOx-bearing (bio)silicas both under suspension conditions and in a flow-through setting. Remarkably, the specific activity of GOx was strongly dependent on the type of diatom biosilica material and in the best case was as high as on synthetic mesoporous silica. Porosity analysis of the materials points to an important role of large mesopores (diameters >20 nm) for supporting a high specific activity of (bio)silica-immobilized GOx.

Metal–organic frameworks are promising candidates for selective separation processes such as CO2removal from methane (natural gas sweetening). Framework flexibility, that is, the ability of a MOF lattice to change its structure as a function of parameters like pressure, temperature, and type of adsorbed molecules, is only observed for some special compounds. The main question of our present work is: does framework flexibility influence the adsorption selectivity? As a direct quantitative method to monitor the adsorption of both, carbon dioxide and methane, we make use of high-pressure in situ 13C NMR spectroscopy of 13CO2/13CH4gas mixtures. This method allows to distinguish between the two gases as well as between adsorbed molecules and the interparticle gas phase. Gas mixture adsorption is studied under isothermal conditions. The selectivity factor for CO2adsorption from CO2/CH4mixtures is measured as a function of total gas pressure. The flexible material SNU-9 as well as the flexible and the nonflexible variant of DUT-8(Ni) are compared. Maximum selectivity factors for CO2are observed for the flexible variant of DUT-8(Ni) in its open, large-pore state. In contrast, the rigid variant of DUT-8(Ni) and SNU-9 especially in its intermediate state exhibits lower adsorption selectivity factors. This observation indicates significant influence of the framework elasticity on the adsorption selectivity.

Recently, we have described the metal–organic framework Ni2(2,6-ndc)2(dabco), denoted as DUT-8(Ni)(1) (DUT = Dresden University of Technology, 2,6-ndc = 2,6-naphthalenedicarboxylate, dabco = 1,4-diazabicyclo[2.2.2]octane). Upon adsorption of molecules such as nitrogen and xenon, this material exhibits a pronounced gate-pressure effect which is accompanied by a large change of the specific volume. Here, we describe the use of high-pressure in situ 129Xe NMR spectroscopy, i.e., the NMR spectroscopic measurements of xenon adsorption/desorption isotherms and isobars, to characterize this effect. It appears that the pore system of DUT-8(Ni) takes up xenon until a liquid-like state is reached. Deeper insight into the interactions between the host DUT-8(Ni) and the guest atom xenon is gained from ab initio molecular dynamics (MD) simulations. van der Waals interactions are included for the first time in these calculations on a metal–organic framework compound. MD simulations allow the identification of preferred adsorption sites for xenon as well as insight into the breathing effect at a molecular scale. Grand canonical Monte Carlo (GCMC) simulations have been performed in order to simulate adsorption isotherms. Furthermore, the favorable influence of a sample pretreatment using solvent exchange and drying with supercritical CO2as well as the influence of repeated pore opening/closure processes, i.e., the “aging behavior” of the compound, can be visualized by 129Xe NMR spectroscopy.

A commercial catalyst (Pt/Vulcan XC 72R) was transformed into a selective electrocatalyst for alcohol oxidation by functionalization of Pt particles with membrane-like metal–organic framework (MOF) coatings of UiO-66 and UiO-66-NO2materials. The electrochemical performance of the MOF-coated electrocatalysts was evaluated using cyclic voltammetric studies in alkaline electrolyte for various alcohols (methanol, ethanol, n-propanol, and n-butanol). The coating modulates the catalytic selectivity, depending on the surface polarity of the MOF material favoring the oxidation of more hydrophilic or more hydrophobic molecules. The adsorption state of alcohols in MOFs was investigated at the molecular level by solid-state NMR experiments. 13C MAS NMR spectroscopy was applied to UiO-66 and UiO-66-NO2loaded with aqueous solutions of isotope-enriched alcohols. To quantitatively detect 13C MAS NMR spectra, single pulse (SP) excitation was used. Cross-polarization was applied to investigate the CP buildup behavior of alcohols in MOFs at different contact times in order to characterize the adsorption state, i.e., the mobility of alcohols in the pores. 1H–13C HETCOR spectra were measured to further characterize the adsorption complexes of alcohols in UiO-66. The experiments demonstrated that the electrocatalytic selectivity originates from the differences in the adsorption strength of primary alcohols in the pores of the MOFs.

A convenient approach for a controlled and high-yield synthesis of copper-deficient Cu3–xP (0.1 < x< 0.7) is reported that makes use of ionic liquids with highly nucleophilic “naked” halide anions. Halide anions drastically enhance the reactivity of the white phosphorus precursor and kinetically disfavor the formation of phosphorus-rich side products. Cu3–xP shows a high degree of tolerance for cation vacancies without major structural reorganization, as evidenced by X-ray diffraction and solid-state nuclear magnetic resonance spectroscopy. Measurements of the electric properties reveal that Cu3–xP is a bad metallic p-type conductor. The resistivity is composition-dependent and displays a distinct anomaly from a phase transition, leading to the discovery and structural characterization of two hitherto unknown low temperature polymorphs. Electrochemical evaluation of copper-deficient Cu3–xP as anode material for lithium ion batteries reveals a drastic change in the cycling mechanism leading to an increase of the initial capacities by about 70%. This work gives a comprehensive insight into the chemical and structural features of copper-deficient Cu3–xP and should lead to an improved understanding of its properties, not just for battery applications.

Biosynthesis by diatoms provides a green approach for nanoparticle (NP) production. However, reproducible and homogeneous shapes are essential for their application. To improve these characteristics during biosynthesis, the underlying synthesis mechanisms as well as involved substances need to be understood. The first essential step for suitable analyses is the purification of Au-silica-nanocomposites from organic biomass. Succesfully cleaned nanocomposites could, for example, be useful as catalysts. In combination with the biosynthesized NPs, this material presents a “green” catalyst and could contribute to the currently thriving green nanochemistry. In this work, we compare different purification agents with respect to their ability to purify cells of the diatom Stephanopyxis turriswithout separating the biosynthesized Au-silica-nanocomposites from the diatom cell walls. Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) are used to localize and identify Au-silica-nanocomposites around the cells. The amount of remaining organic compounds on the purified cell is detected by attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy. Furthermore, inductively coupled plasma optical emission spectrometry (ICP-OES) is used to track the “gold path” during cell growth and the different purifications steps.

One of the main problems of gas storage in porous materials is that many molecules of interest adsorb too weakly to be retained effectively. To enhance gas storage in metal–organic frameworks (MOFs), we propose the use of kinetic trapping, i.e., a process where the guest gas is captured in the voids at loading conditions and not released immediately at normal conditions. In this approach, the diffusion-limiting pore size and the framework flexibility have to be matched to the gas, requiring flexible pore apertures to be smaller than the van der Waals diameter of the trapped guest. We selected the Metal–Organic Framework Ulm University-4 (MFU-4) with a pore aperture of 2.52 Å as a model coordination framework and used it for storage of xenon (with van der Waals diameter of 4.4 Å). Although xenon atoms are substantially larger than the MOF pore aperture, MFU-4 could be loaded with xenon by applying moderately high gas pressures. This is demonstrated to be due to the pore flexibility as confirmed by computational studies. The xenon loading could be tuned (from 0 wt % to more than 44.5 wt %) by changing the loading parameters such as pressure, temperature, and time, and the xenon atoms remained inside the pores upon exposing the material to air atmosphere at room temperature. To understand the material behavior, TGA, XRPD, and 129Xe NMR spectroscopy and computational studies were carried out.

Abstract

Diatoms contribute 20% of global primary production and form the basis of many marine food webs. Although their species diversity correlates with broad diversity in cell size, there is also an intraspecific cell-size plasticity owing to sexual reproduction and varying environmental conditions. However, despite the ecological significance of the diatom cell size for food-web structure and global biogeochemical cycles, our knowledge about genes underpinning the size of diatom cells remains elusive. Here, a combination of reverse genetics, experimental evolution and comparative RNA-sequencing analyses enabled us to identify a previously unknown genetic control of cell size in the diatom Thalassiosira pseudonana. In particular, the targeted deregulation of the expression of the cell-wall protein silacidin caused a significant increase in valve diameter. Remarkably, the natural downregulation of the silacidin gene transcript due to experimental evolution under low temperature also correlated with cell-size increase. Our data give first evidence for a genetically controlled regulation of cell size in T. pseudonana and possibly other centric diatoms as they also encode the silacidin gene in their genomes.

Diatoms contribute 20% of global primary production and form the basis of many marine food webs. Although their species diversity correlates with broad diversity in cell size, there is also an intraspecific cell-size plasticity owing to sexual reproduction and varying environmental conditions. However, despite the ecological significance of the diatom cell size for food-web structure and global biogeochemical cycles, our knowledge about genes underpinning the size of diatom cells remains elusive. Here, a combination of reverse genetics, experimental evolution and comparative RNA-sequencing analyses enabled us to identify a previously unknown genetic control of cell size in the diatom Thalassiosira pseudonana.In particular, the targeted deregulation of the expression of the cell-wall protein silacidin caused a significant increase in valve diameter. Remarkably, the natural downregulation of the silacidin gene transcript due to experimental evolution under low temperature also correlated with cell-size increase. Our data give first evidence for a genetically controlled regulation of cell size in T. pseudonanaand possibly other centric diatoms as they also encode the silacidin gene in their genomes.

The pronounced flexibility of special metal–organic frameworks (MOFs), so-called soft porous crystals, is attracting increasing research interest. Studies of host–guest interactions in such materials are especially powerful if the measurements are performed in situ. 129Xe NMR spectroscopy is favorable because it provides characteristic, structure-sensitive parameters such as chemical shifts. The combination of high-pressure xenon adsorption with 129Xe NMR spectroscopy was used to elucidate the adsorption-induced phase transitions in the recently discovered pressure-amplifying framework material DUT-49, showing a unique negative gas adsorption (NGA) transition. In the open-pore state, DUT-49op exhibits a hierarchical pore system involving both micro- and mesopores. After reaching a critical relative pressure of ca. 0.15, adsorbed xenon induces mesopore contraction, resulting in a purely microporous contracted-pore phase. This contraction is accompanied by release of xenon from the mesopores. Further increase of the pressure initiates the recovery of the mesopores without any indication of a structural intermediate in the NMR spectra. According to the NMR data, the structural transition induced by xenon is a collective, stepwise phenomenon rather than a continuous process. This is the first time that NGA has been studied by directly monitoring the guest and its interaction with the host framework.

We report on a simple and effective technique of tuning the colloidal solubility of inorganic-capped CdSe and CdSe/CdS core/shell nanocrystals (NCs) from highly polar to nonpolar media using n-butylamine molecules. The introduction of the short and volatile organic amine mainly results in a modification of the labile diffusion region of the inorganic-capped NCs, enabling a significant extension of their dispersibility and improving the ability to form long-range assemblies. Moreover, the hybrid n-butylamine/inorganic capping can be thermally decomposed under mild heat treatment, making this approach of surface functionalization well-compatible with a low-temperature, solution-processed device fabrication. Particularly, a field-effect transistor-based on n-butylamine/Ga-I-complex-capped 4.5 nm CdSe NC solids shows excellent transport characteristics with electron mobilities up to 2 cm2/(V·s) and a high current modulation value (>104) at a low operation voltage (<2 V).

Polycrystalline Cu3–xP was successfully synthesized in different ionic liquids comprising imidazolium and phosphonium cations. The reaction of elemental copper and red phosphorus in trihexyltetradecylphosphonium chloride at 200 °C led to single-phase Cu3–xP (x= 0.05) within 24 h with a quantitative yield (99%). Liquid-state nuclear magnetic resonance spectroscopy of the ionic liquids revealed degeneration of the imidazolium cations under the synthesis conditions, while phosphonium cations remain stable. The solid products were characterized with X-ray powder diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, solid-state nuclear magnetic resonance spectroscopy, and elemental analysis. A reinvestigation of the electronic transport properties of Cu2.95(4)P showed metallic behavior for the bulk material. The formation of CuP2during the synthesis of phosphorus-rich Cu3–xP (x≥ 0.1) was observed.