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The enzymatic degradation of aliphatic polyesters offers unique opportunities for various use cases in materials science. Although evidently desirable, the implementation of enzymes in technical applications of polyesters is generally challenging due to the thermal lability of enzymes. To prospectively overcome this intrinsic limitation, we here explored the thermal stability of proteinase K at conditions applicable for polymer melt processing, given that this hydrolytic enzyme is well established for its ability to degrade poly(l-lactide) (PLLA). Using assorted spectroscopic methods and enzymatic assays, we investigated the effects of high temperatures on the structure and specific activity of proteinase K. Whereas in solution, irreversible unfolding occurred at temperatures above 75-80 °C, in the dry, bulk state, proteinase K withstood prolonged incubation at elevated temperatures. Unexpectedly little activity loss occurred during incubation at up to 130 °C, and intermediate levels of catalytic activity were preserved at up to 150 °C. The resistance of bulk proteinase K to thermal treatment was slightly enhanced by absorption into polyacrylamide (PAM) particles. Under these conditions, after 5 min at a temperature of 200 °C, which is required for the melt processing of PLLA, proteinase K was not completely denatured but retained around 2% enzymatic activity. Our findings reveal that the thermal processing of proteinase K in the dry state is principally feasible, but equally, they also identify needs and prospects for improvement. The experimental pipeline we establish for proteinase K analysis stands to benefit efforts directed to this end. More broadly, our work sheds light on enzymatically degradable polymers and the thermal processing of enzymes, which are of increasing economical and societal relevance.

Swelling of clays is hampered by increasing layer charge. With vermiculite-type layer charge densities, crystalline swelling is limited to the two-layer hydrate, while osmotic swelling requires ion exchange with bulky and hydrophilic organic molecules or with Li

We demonstrate an efficient strategy to characterise weathering-induced photooxidative defects in microplastics. The central 13C cross polarisation NMR spectra offer high resolution and are quantitative when combined with multiple excitation.

Potassium 15-crown-5 phenanthrenide and potassium 18-crown-6 phenanthrenide were synthesized and characterized by powder X-ray diffraction and 39K solid state NMR spectroscopy. While the radical carbanion is very reactive in solution, the crystals are stable and storable under inert atmosphere. For 15-crown-5, a sandwich-like complex of potassium is formed with two molecules of crown ether per potassium resulting in a coordination number of 10. For the larger 18-crown-6 ligand, a 1:1 complex is obtained and a coordination number of 6 for the potassium cation. In neither crystal structure solvent molecules are incorporated. The 15-crown-5 compound crystallizes faster and is less soluble in THF as compared to the 18-crown-6 compound. Both compounds form solid phenanthrenide that is easy to handle and can be applied for reduction reactions.

In forest ecosystems, decomposition is essential for carbon and nutrient cycling and therefore a key process for ecosystem functioning. During the decomposition process, litter chemistry, involved decomposer organisms, and enzymatic activity change interdependently. Chemical composition of the litter is the most complex and dynamic component in the decomposition process and therefore challenging to assess holistically. In this study, we aimed to characterize chemical shifts during decomposition and link them to changes in decomposer fungal activity. We characterized the chemical composition of freshly fallen autumn leaves of European beech (Fagus sylvatica) and the corresponding leaf litter after 1 year of decomposition by proton nuclear magnetic resonance spectroscopy. We further tested the applicability of spiking experiments for qualitative and quantitative characterization of leaves and litter chemistry. The composition and transcriptional activity of fungal communities was assessed by high-throughput Illumina sequencing in the same litter samples. We were able to distinguish freshly fallen leaves from 1-year-old litter based on their chemical composition. Chemical composition of leaves converged among regions with progressing decomposition. Fungal litter communities differed in composition among regions, but they were functionally redundant according to the expression of genes encoding litter degrading enzymes (CAZymes). Fungi of the saprotrophic genera Mycena and Chalara correlated with transcription of litter-degrading CAZymes in 1-year-old litter. Forestry measures influenced the diversity and transcription rate of the detected CAZymes transcripts in litter. Their expression was primarily predicted by composition of the soluble chemical fraction of the litter. Environmental NMR fingerprints thus proved valuable for inferring ecological contexts. We propose and discuss a holistic framework to link fungal activity, enzyme expression, and chemical composition.

We report on a new photocatalytic system that consists of an iridium-based photosensitizer that has been encapsulated into the pores of the metal–organic framework (MOF) MIL-101, which have then be...

The fragmentation of macro- into microplastics (MP) is the main source of MP in the environment. Nevertheless, knowledge about degradation mechanisms, changes in chemical composition, morphology, and residence times is still limited. Here, we present a long-term accelerated weathering study on polystyrene (PS) tensile bars and MP particles using simulated solar radiation and mechanical stress. The degradation process was monitored by gel permeation chromatography (GPC), scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), 13C magic-angle spinning (MAS) NMR spectroscopy, tensile testing, and Monte Carlo simulations. We verified that degradation proceeds in two main stages. Stage I is dominated by photooxidation in a near-surface layer. During stage II, microcrack formation and particle rupturing accelerate the degradation. Depending on the ratio and intensity of the applied stress factors, MP degradation kinetics and lifetimes vary dramatically and an increasing amount of small MP fragments with high proportions of carboxyl, peroxide, and keto groups is continuously released into the environment. The enhanced surface area for adsorbing pollutants and forming biofilms modifies the uptake behavior and interaction with organisms together with potential ecological risks. We expect the proposed two-stage model to be valid for predicting the abiotic degradation of other commodity plastics with a carbon-carbon backbone.

With regard to upcoming regulations of common chemical blowing agents for epoxy foams, carbamates provide suitable alternatives. They act as blowing agents releasing CO2 and cure epoxy resins after...

Nanostructured and reusable 3d‐metal catalysts that operate with high activity and selectivity in important chemical reactions are highly desirable. Here, a cobalt catalyst was developed for the synthesis of primary amines via reductive amination employing hydrogen as the reducing agent and easy‐to‐handle ammonia, dissolved in water, as the nitrogen source. The catalyst operates under very mild conditions (1.5 mol% catalyst loading, 50 °C and 10 bar H2 pressure) and outperforms commercially available noble metal catalysts (Pd, Pt, Ru, Rh, Ir). A broad scope and a very good functional group tolerance were observed. The key for the high activity seemed to be the used support: an N‐doped amorphous carbon material with small and turbostratically disordered graphitic domains, which is microporous with a bimodal size distribution and with basic NH functionalities in the pores., Reductive amination: A nanostructured highly active cobalt catalyst is employed for the reductive amination of ketones and aldehydes by ammonia and H2 under very mild conditions. A broad substrate scope and very good functional group tolerance are observed. Detailed analysis of the catalyst's chemical and physical nature provides key reasons for its extraordinary activity, outperforming noble metal catalysts.

The efficiency of dynamic nuclear polarization (DNP) enhanced 19F MAS NMR spectroscopy without 19F-containing solvents and matrices, which transport polarization via 19F–19F spin diffusion, is demo...

Ni-rich Li(Ni1–x–yCoxMny)O2-based cathodes still suffer from low cycling stability, which arises from capacity fading and impedance rise due to parasitic side reactions at the interface. Surface co...

Microporous organic polyimides are promising materials to be used as adsorbents to remove carbon dioxide from flue gases by physisorptive separation processes. Especially, ultramicroporous systems often exhibit excellent CO2 selectivities and uptakes. Ultramicroporosity is usually achieved by using small linkers, making conventional synthesis routes challenging due to the stress in the resulting networks. Using toluene as an entraining agent, we were able to synthesise two new microporous organic polyimides – MOPI-6 and MOPI-7 – with very small linker molecules. The composition of the solvent mixture m-cresol/toluene was varied and all polymers were characterised using 13C and 15N CP MAS NMR as well as IR spectroscopy, CHN, PXRD, TGA, SEM and physisorption. Both polymer series exhibit high crosslinking degrees, and the systems prepared in m-cresol/toluene mixtures show ultra- and supermicroporosity with CO2 uptakes comparable with values for systems reported in the literature. By preferentially adsorbing CO2, which blocks the accessible pore space for methane, these systems feature outstanding selectivity values up to 72 for CO2/CH4 mixtures. Additionally, they exhibit a sponge-like morphology resulting in unusual hierarchical porosity, which we attribute to pronounced boiling of the solvent mixture by adjusting the solvent polarity to the polymer particle surface properties. The hierarchical porosity reduces diffusion paths and thus avoids kinetic hindrances important in dynamic sorption processes used in industrial relevant applications like pressure (PSA), vacuum (VSA) or temperature swing adsorption (TSA). Thus, we consider the use of solvent mixtures with strong boiling point differences as an approach to synthesise hierarchical porous polymers, which is applicable for a wide range of porous polymers.

Acetic acid, an alternative green solvent, was utilized for the solvothermal synthesis of four 2D materials of composition [Zr2O2(OAc)2(BDC-F)], [Zr2O2(OAc)2(BDC-F4)], [Zr2O2(OAc)2(BDC)], and [Zr2O...

Oxygen-17 spin relaxation and stimulated-echo experiments are carried out to study temperature-dependent reorientational time scales in potassium permanganate. From an analysis of the present data, an energy barrier of 0.35 eV is found. This activation energy is much larger than the one reported previously (Jakobsen et al. Quantitative Dynamics and Structure for Crystalline Cs2WO4 and KMnO4 Determined from High-Field 17O Variable-Temperature MAS NMR Experiments, J. Phys. Chem. C 2014, 118, 20639–20646), but it is on the order of magnitude expected from observations for the dynamics of other tetraoxoanions in ionic crystals. The various contributions to the measured spin relaxation times and details regarding the two-time correlation functions for KMnO4 are discussed.

Increasing dynamics in solids featuring nuclei subjected to second-order quadrupolar interactions lead to central-transition spectra that undergo two consecutive line-shaped transitions. Conventional motional narrowing occurs when the molecular exchange rate is on the order of the strength of the dominant interaction. In a second step, the resulting intermediately narrowed spectra change further when the motion becomes faster than the Larmor precession rate, leading to terminally narrowed spectra that can display a residual quadrupolar shift. We derive analytic expressions for this shift and analyze the quadrupolar central-transition spectra in terms of CN symmetrical cone models. Increasing the number of sites to N ≥ 3, the terminally narrowed spectra remain unaltered, while the intermediately narrowed spectra remain unaltered only for N ≥ 5. This finding relates to the different (cubic vs. icosahedral) symmetries that are required to average out the spatial second- and fourth-rank terms in the second-order quadrupolar interaction. Following recent work (Hung et al., Solid State Nucl Magn Reson 84:14–19, 2017), 17O NMR is applied to examine the three-site rotation of the nitrate group in NaNO3. Line shapes are measured and analyzed, and in addition to prior work, satellite-transition and stimulated-echo experiments are carried out. The final-state amplitudes extracted from the latter are reproduced using model calculations. It is shown how two-dimensional exchange spectra relating to N-site cone motions can be decomposed in terms of effective two-site-jump spectra. This latter approach is successfully tested for NaNO3.

La3 B6 O13 (OH) was obtained by a high-pressure/high-temperature experiment at 6 GPa and 1673 K. The compound crystallizes in the space group P21 (no. 4) with the lattice parameters a=4.785(2), b=12.880(4), c=7.433(3) A, and β=90.36(10)°, and is built up of corner- as well as edge-sharing BO4 tetrahedra. It represents the first acentric high-pressure borate containing these B2 O6 entities. The compound develops borate layers of "sechser"-rings with the La3+ cations positioned between the layers. Single-crystal and powder X-ray diffraction, vibrational and MAS NMR spectroscopy, second-harmonic generation (SHG) and thermoanalytical measurements, as well as computational methods were used to affirm the proposed structure and the B2 O6 entities.

The extraordinary sensitivity of

Controlling the solid-state morphology of semiconducting polymers is crucial for the function and performance of optoelectronic and photonic devices. Nucleation is a commonly used and straightforward approach to tailor the solid-state morphology of semi-crystalline polymers. However, efficient nucleating agents for semiconducting polymers are still rare. Here, we present a conceptual approach to tailor supramolecular nucleating agents for the semiconducting polymer, poly(3-hexylthiophene) (P3HT). Using this approach, we developed a class of supramolecular nucleating agents, which can achieve outstanding nucleation efficiencies of more than 95% at concentrations as low as 0.1 wt %. Such efficiencies can be achieved by combining an exceptionally high epitaxial match with highly regularly arranged donor-acceptor interactions between the nucleating agent and the polymer. Notably, the supramolecular agents do not induce trap states in thin films of P3HT and are beneficial for the film stability by controlling the solid-state morphology. We anticipate that this approach can be transferred to other semi-crystalline conjugated polymers, resulting in defined solid-state morphologies.

When plastics enter the environment, they are exposed to abiotic and biotic impacts, resulting in degradation and the formation of micro- and nanoplastic. Microplastic is ubiquitous in every environmental compartment. Nevertheless, the underlying degradation processes are not yet fully understood. Here, we studied the abiotic degradation of commonly used semi-crystalline, low-density polyethylene (LDPE) in a long-term accelerated weathering experiment combining several macro- and microscopic methods. Based on our observations, the degradation of LDPE proceeds in three stages. Initially, LDPE objects are prone to abrasion, followed by a period of surface cracking. A large number of secondary particles with a high degree of crystallinity are formed, with sizes down to the nanometer scale. These particles consist of highly polar oligomers leading to agglomeration in the final stage. We therefore suppose that weathered microplastic and nanoplastic particles will attach to colloidal environmental matter. This offers an explanation for the absence of free nanoplastic particles in natural samples.

Benzene bisamides are promising building blocks for supramolecular nano-objects. Their functionality depends on morphology and surface properties. However, a direct link between surface properties and molecular structure itself is missing for this material class. Here, we investigate this interplay for two series of 1,4-benzene bisamides with symmetric and asymmetric peripheral substitution. We elucidated the crystal structures, determined the nano-object morphologies and derived the wetting behaviour of the preferentially exposed surfaces. The crystal structures were solved by combining single-crystal and powder X-ray diffraction, solid-state NMR spectroscopy and computational modelling. Bulky side groups, here t-butyl groups, serve as a structure-directing motif into a packing pattern, which favours the formation of thin platelets. The use of slim peripheral groups on both sides, in our case linear perfluorinated, alkyl chains, self-assemble the benzene bisamides into a second packing pattern which leads to ribbon-like nano-objects. For both packing types, the preferentially exposed surfaces consist of the ends of the peripheral groups. Asymmetric substitution with bulky and slim groups leads to an ordered alternating arrangement of the groups exposed to the surface. This allows the hydrophobicity of the surfaces to be gradually altered. We thus identified two leitmotifs for molecular packings of benzene bisamides providing the missing link between the molecular structure, the anisotropic morphologies and adjustable surface properties of the supramolecular nano-objects.

Solving the structure of carbon nitrides has been a long-standing challenge due to the low crystallinity and complex structures observed within this class of earth-abundant photocatalysts. Herein, we report on two-dimensional layered potassium poly(heptazine imide) (K-PHI) and its proton-exchanged counterpart (H-PHI), obtained by ionothermal synthesis using a molecular precursor route. We present a comprehensive analysis of the in-plane and three-dimensional structure of PHI. Transmission electron microscopy and solid-state NMR spectroscopy, supported by quantum-chemical calculations, suggest a planar, imide-bridged heptazine backbone with trigonal symmetry in both K-PHI and H-PHI, whereas pair distribution function analyses and X-ray powder diffraction using recursive-like simulations of planar defects point to a structure-directing function of the pore content. While the out-of-plane structure of K-PHI exhibits a unidirectional layer offset, mediated by hydrated potassium ions, H-PHI is characterized by a high degree of stacking faults due to the weaker structure directing influence of pore water. Structure-property relationships in PHI reveal that a loss of in-plane coherence, materializing in smaller lateral platelet dimensions and increased terminal cyanamide groups, correlates with improved photocatalytic performance. Size-optimized H-PHI is highly active toward photocatalytic hydrogen evolution, with a rate of 3363 mu mol/gh H-2 placing it on par with the most active carbon nitrides. K- and H-PHI adopt a uniquely long-lived photoreduced polaronic state in which light-induced electrons are stored for more than 6 h in the dark and released upon addition of a Pt cocatalyst. This work highlights the importance of structure- property relationships in carbon nitrides for the rational design of highly active hydrogen evolution photocatalysts.

Aqueous aluminum(III) solutions at medium pH are used for industrial applications such as cement adjuvants. The necessary high Al3+ concentrations are achieved by using complexing ligands, such as lactic acid, to prevent precipitation. Here, we grew crystals from commercially available neutralized aluminum lactate solutions to derive an understanding of the underlying aluminum lactate chemistry. Using X-ray diffraction in combination with multinuclear NMR spectroscopy and quantum mechanical calculations, we found that the crystals have a stoichiometry of Na3[Al(l-lactate)3]2·6H2O and consist of negatively charged [Al(l-lactate)3]23– bis-clusters. The remarkable stability of these clusters is achieved by linking both Al(l-lactate)3 subunits via three very short symmetrical hydrogen bonds between the α-hydroxy groups with half of them being deprotonated. The trends for both the 27Al chemical shift and the spin–spin relaxation for the Lohtragon-type solutions as a function of pH suggest the bis-cluster to be...

A new preparation route is developed for the synthesis of needle-like crystals of [Au(S2 CNH2 )2 ]SCN, which avoids disproportionation of the AuI salt used as a starting material. In the crystal structure, the two crystallographically independent AuIII centers are in a square-planar environment of two S2 CNH2 ligands. The Hirshfeld surface analysis reveals the presence of noncovalent intermolecular S⋅⋅⋅S interactions, which are essential for the spatial arrangement of the molecules. Density functional theory (DFT) calculations including dispersion and damping corrections result in a unit cell volume very close to the value determined experimentally. Thermal decomposition in an inert atmosphere generates black needles with lengths of up to 500 μm. X-ray powder diffraction and pair distribution function analyses demonstrate that the needles are composed of nanosized crystals with a volume-weighted average domain size of 20(1) nm. According to results of X-ray photoemission experiments, the black needles are covered by a nitrogen-rich carbon nitride with composition near (CN)2 N. 13 C solid-state NMR investigations indicate that two different carbon species are present, with signals corresponding well to heptazine units as in melon and triazine units as in poly(triazin imide) type compounds. Scanning transmission electron microscopy tomography evidences that the needles are composed of slightly elongated nanoparticles.

A diode requires the combination of p- and n-type semiconductors or at least the defined formation of such areas within a given compound. This is a prerequisite for any IT application, energy conversion technology, and electronic semiconductor devices. Since the discovery of the pnp-switchable compound Ag

Microplastic particles (MPs) are a major threat to ecosystems worldwide, resulting in a great need to investigate their impacts on ecosystems. To date, most studies dealing with the effects of MPs on organisms used commercially available polystyrene spherical particles, with no to little characterization of their physicochemical properties. However, MPs occurring in the environments are a composition of various polymer types with different properties. Therefore, it is hard to tell how and if the polymer type and its associated properties determine their impact on organisms. Here we show how different polymer types of MPs in the same shape, concentration, and size range (20-120µm) affect the freshwater mussel Dreissena bugensis in comparison to mussel shell fragments as natural particle control. By using hall sensor-based real-time valvometry, we studied behavioural responses via the movement of the mussels' valves and show that mussels cannot distinguish between natural particles and MPs. Furthermore, we performed an in-depth characterization of the used MPs. Different types and quantities of additives and residual monomers were found in the different polymer types, which can be linked to polymer type-dependent adverse effects on the molecular level. Recycled PET elicited the most substantial adverse effects on D. bugensis, likely caused by anthranilamide, anthranilonitrile and butylated hydroxytoluene within the MP fragments, which have been described as toxic to aquatic organisms. Since PET is among the most abundant MPs found in nature, sublethal effects may gradually manifest at the population level, leading to irreversible ecosystem changes. In summary, adverse effects in organisms caused by MPs are dependent on specific physical and chemical properties of the particles. Also see: https://micro2022.sciencesconf.org/428254/document, In MICRO 2022, Online Atlas Edition: Plastic Pollution from MACRO to nano

Polystyrene foams have become more and more important owing to their lightweight potential and their insulation properties. Progress in this field is expected to be realized by foams featuring a microcellular morphology. However, large-scale processing of low-density foams with a closed-cell structure and volume expansion ratio of larger than 10, exhibiting a homogenous morphology with a mean cell size of approximately 10 mu m, remains challenging. Here, we report on a series of 4,4 `-diphenylmethane substituted bisamides, which we refer to as kinked bisamides, acting as efficient supramolecular foam cell nucleating agents for polystyrene. Self-assembly experiments from solution showed that these bisamides form supramolecular fibrillary or ribbon-like nanoobjects. These kinked bisamides can be dissolved at elevated temperatures in a large concentration range, forming dispersed nano-objects upon cooling. Batch foaming experiments using 1.0 wt.% of a selected kinked bisamide revealed that the mean cell size can be as low as 3.5 mu m. To demonstrate the applicability of kinked bisamides in a high-throughput continuous foam process, we performed foam extrusion. Using 0.5 wt.% of a kinked bisamide yielded polymer foams with a foam density of 71 kg/m(3) and a homogeneous microcellular morphology with cell sizes of approximate to 10 mu m, which is two orders of magnitude lower compared to the neat polystyrene reference foam with a comparable foam density.

Porphyrin-based metal-organic frameworks (MOFs), exemplified by the prototypical representatives MOF-525, PCN-221, and PCN-224 are among the most promising MOF systems for catalysis, optoelectronics, and solar energy conversion. However, subtle differences between synthetic protocols for these three MOFs give rise to vast discrepancies in purported product outcomes and description of framework topologies. Here, we reveal the type and disorder of the Zr-clusters based on a comprehensive synthetic and structural analysis spanning local and long-range length scales. Our analysis on PCN-221 reveals Zr6O4(OH)4 clusters in four distinct orientations within the unit cell, rather than Zr8O6 clusters as originally published, accompanied by random linker vacancies around 50%. We propose disordered PCN-224 (dPCN-224) as a unified model to understand PCN-221, MOF-525, and PCN-224 by varying the degree of orientational cluster disorder, linker conformation and vacancies, and cluster—linker binding. Our work thus introduces a new perspective on network topology and disorder in Zr-MOFs and pinpoints the structural variables that direct their functional properties.

Herein is reported the utilization of acetonitrile as a new solvent for the synthesis of the three significantly different benchmark metal–organic frameworks (MOFs) CAU‐10, Ce‐UiO‐66, and Al‐MIL‐53 of idealized composition [Al(OH)(ISO)], [Ce6O4(OH)4(BDC)6], and [Al(OH)(BDC)], respectively (ISO2−: isophthalate, BDC2−: terephthalate). Its use allowed the synthesis of Ce‐UiO‐66 on a gram scale. While CAU‐10 and Ce‐UiO‐66 exhibit properties similar to those reported elsewhere for these two materials, the obtained Al‐MIL‐53 shows no structural flexibility upon adsorption of hydrophilic or hydrophobic guest molecules such as water and xenon and is stabilized in its large‐pore form over a broad temperature range (130–450 K). The stabilization of the large‐pore form of Al‐MIL‐53 was attributed to a high percentage of noncoordinating −COOH groups as determined by solid‐state NMR spectroscopy. The defective material shows an unusually high water uptake of 310 mg g−1 within the range of 0.45 to 0.65 p/p°. In spite of showing no breathing effect upon water adsorption it exhibits distinct mechanical properties. Thus, mercury intrusion porosimetry studies revealed that the solid can be reversibly forced to breathe by applying moderate pressures (≈60 MPa)., Metal–organic frameworks: CAU‐10, Ce‐UiO‐66, and Al‐MIL‐53 were synthesized by utilizing acetonitrile as the solvent. The typical breathing behavior of Al‐MIL‐53 upon guest molecule adsorption was inhibited by a high concentration of defects. As shown by NMR spectroscopy these consist of noncoordinated −COOH groups. Breathing could be enforced by applying a pressure of about 60 MPa during mercury intrusion.

Microplastics and its putative adverse effects on environmental and human health increasingly gain scientific and public attention. Systematic studies on the effects of microplastics are currently hampered by using rather poorly characterised particles, leading to contradictory results for the same particle type. Here, surface properties and chemical composition of two commercially available nominally identical polystyrene microparticles, frequently used in effect studies, were characterised. We show distinct differences in monomer content, ζ-potentials and surface charge densities. Cells exposed to particles showing a lower ζ-potential and a higher monomer content displayed a higher number of particle-cell-interactions and consequently a decrease in cell metabolism and proliferation, especially at higher particle concentrations. Our study emphasises that no general statements can be made about the effects of microplastics, not even for the same polymer type in the same size class, unless the physicochemical properties are well characterised.

Applying a nematic liquid crystalline phase of a synthetic Na-hectorite with layer separations >100 nm, the reaction time for pillaring with Al13 Keggin oligocation could be reduced to seconds ensuring that cation exchange is controlled by thermodynamics. With this material at hand we are able to resolve the long-standing dispute regarding the charge of intercalated Keggin oligocations. Micropore sizes as determined by physisorption isotherms, adsorption isotherms obtained via elemental analysis, and results of 27Al solid-state NMR and pyridine probe IR spectroscopy favor a charge of +7 for the Al13 pillars intercalated into hectorite unaltered.

Two new chalcogenogallates Cs(4)Ga(6)Q(11) (Q = S, Se) were obtained by a controlled thermal treatment of CsN3 in the presence of stoichiometric amounts of Ga(2)Q(3) and the elemental chalcogens at elevates temperatures. Both isotypic compounds crystallize in the space group P (1) over bar (no. 2). The most prominent structural feature in these chalcogenogallates are the complex anionic Dreier double chains (1)(infinity)[Ga(6)Q(11)(4-)] formed by condensed GaQ(4) tetrahedra. The semiconductors Cs4Ga6S11 (E-g = 3.14 eV) and Cs4Ga6Se11 (E-g = 2.41 eV) were further studied by using UV/Vis, Cs-133 and Ga-71 solid-state NMR spectroscopy, and complementary DFT calculations. The Cs-133 MAS NMR spectra are characteristic for cationic cesium and vibrational spectra show two distinct regions, attributed to the Ga-Q valence and deformation vibrations, respectively. High-temperature studies revealed incongruent melting of both solids, which is also depicted in updated binary phase-diagrams Cs(2)Q-Ga(2)Q(3) (Q = S, Se).

The design of microporous hybrid materials, tailored for diverse applications, is a key to address our modern society's imperative of sustainable technologies. Prerequisites are flexible customization of host-guest interactions by incorporating various types of functionality and by adjusting the pore structure. On that score, metal-organic frameworks (MOFs) have been the reference in the past decades. More recently, a new class of microporous hybrid materials emerged, microporous organically pillared layered silicates (MOPS). MOPS are synthesized by simple ion exchange of organic or metal complex cations in synthetic layered silicates. MOFs and MOPSs share the features of "component modularity" and "functional porosity". While both, MOFs and MOPS maintain the intrinsic characteristics of their building blocks, new distinctive properties arise from their assemblage. MOPS are unique since allowing for simultaneous and continuous tuning of micropores in the sub-Ångström range. Consequently, with MOPS the adsorbent recognition may be optimized without the need to explore different framework topologies. Similar to the third generation of MOFs (also termed soft porous crystals), MOPS are structurally ordered, permanently microporous solids that may also show a reversible structural flexibility above a distinct threshold pressure of certain adsorbents. This structural dynamism of MOPS can be utilized by meticulously adjusting the charge density of the silicate layers to the polarizability of the adsorbent leading to different gate opening mechanisms. The potential of MOPS is far from being fully explored. This Concept article highlights the main features of MOPS and illustrates promising directions for further research.

The sorption properties of metal–organic frameworks (MOFs) can be influenced by introducing covalently attached functional side chains, which make this subclass of porous materials promising for applications as diverse as gas storage and separation, catalysis, and drug delivery. The incorporation of side groups usually comes along with disorder, as the synthesis procedures rarely allow for one specific position among a larger group of equivalent sites to be selected. For a series of isoreticular CAU-1 frameworks, chosen as model compounds, one out of four positions at every linker is modified with equal probability. Here, we investigate the influence of this disorder on Ar sorption and 129Xe nuclear magnetic resonance spectroscopy using hyperpolarized 129Xe gas. Models used for predicting the pore dimensions as well as their distributions were derived from the unfunctionalized framework by replacing one proton at every linker with either an amino, an acetamide, or a methyl urea functionality. The resultin...

Polycrystalline dimethyl sulfone is studied using central-transition oxygen-17 exchange NMR. The quadrupolar and chemical shift tensors are determined by combining quantum chemical calculations with line shape analyses of rigid-lattice spectra measured for stationary and rotating samples at several external magnetic fields. Quantum chemical computations predict that the largest principal axes of the chemical shift anisotropy and electrical field gradient tensors enclose an angle of about 73°. This prediction is successfully tested by comparison with absorption spectra recorded at three different external magnetic fields. The experimental one-dimensional motionally narrowed spectra and the two-dimensional exchange spectrum are compatible with model calculations involving jumps of the molecules about their two-fold symmetry axis. This motion is additionally investigated by means of two-time stimulated-echo spectroscopy which allows for a determination of motional correlation functions over a wider temperature range than previously reported using carbon and deuteron NMR. On the basis of suitable second-order quadrupolar frequency distributions, sin-sin stimulated-echo amplitudes are calculated for a two-site model in the limit of vanishing evolution time and compared with experimental findings. The present study thus establishes oxygen-17 NMR as a powerful method that will be particularly useful for the study of solids and liquids devoid of nuclei governed by first-order anisotropies.

Microporous organic polyimides are well suited for carbon dioxide separation from gas mixtures based on their polar surface and their tendency towards ultramicroporosity. Nevertheless, their application potential is limited due to an inherent insolubility and infusibility, preventing an easy processing into functional objects like membranes. By establishing a three-step synthesis procedure for the literature known network NPI-I, here, a solution to this challenge is demonstrated. The central step is electrospinning of a solution of the linkers tetrakis(4-aminophenyl)methane and naphthalene 1,4,5,8-tetracarboxylic dianhydride and the auxiliary polymer polyvinylpyrrolidone into a precursor fiber mat. The mat was then heated to polymerize the linkers into the polyimide. Subsequently, PVP was removed by pyrolysis obtaining a robust, flexible and self-standing membrane. The NPI-I fiber mat exhibits a remarkable microporosity with a BET surface area of 222 m2/g, a total pore volume of 0.121 cm3/g and a high amount of ultramicropores. Its CO2 uptake of 3.0 mmol/g (0 °C, 1 bar) and its CO2/CH4 selectivity of about 20 (0 °C, 1 bar) even exceed the literature values for bulk NPI-I. This study reveals that PVP acts as a template on molecular level influencing, primarily the micropore formation, reducing the BET surface area by roughly a factor of three compared to the bulk material. In contrast, the ultramicroporosity of the porous polyimides remains mainly unaffected. We envision that this three-step synthesis can be transferred to a broad variety of porous polymers. With electrospinning the large-scale production of self-standing membranes becomes realistic rendering the application of porous polymers for gas separation more likely.