This paper focuses on the activation of boro-alumino-silicate glass from discarded pharmaceutical containers as fine powders suspended in relatively diluted alkaline solutions (2.5 M NaOH/KOH), followed by drying at 40°C for 7 days. A specific molecular mechanism of glass hardening is proposed. Unlike geopolymers, the hardening does not result from the condensation of products of extensive dissolution. Instead, condensation reactions occur in hydrated surface layers, leading to strong bonds (Si-O-Si, Al-O-Si, etc.) between individual glass particles. Silicates, borates, and aluminates from glass dissolution combine with alkaline ions, yielding additional soluble phases. This mechanism is supported by the results of solid-state NMR spectroscopy and elemental analysis using ICP-OES. Stable matrices prepared by direct foaming or by the inclusion of cenospheres or commercial expanded glass (Poraver®) can be exploited for the fabrication of lightweight components

Understanding the atomic-scale local properties of solid solutions is crucial for deciphering their structure-property relationships. In this work, we present a computational approach that combines solid-state nuclear magnetic resonance (NMR) spectroscopy with density functional theory (DFT) calculations to investigate local chemical environments in solid solutions. Previous canonical ensemble models, which only sample configurations at a fixed composition of the simulation cell, fail to capture local compositional fluctuations that can significantly influence the NMR spectra. To address this limitation, we employ a grand-canonical ensemble approach enabling a more comprehensive representation of the contributions of all possible local chemical environments to the NMR spectrum, using a La2(Zr1-x Sn x )2O7 pyrochlore solid solution as a case study. To mitigate the high computational cost of such simulations, we also explore ensemble truncation strategies and the use of machine learning (ML) to aid predictions of NMR chemical shifts, achieving a significant reduction in computational cost while maintaining most of the predictive power. Our results show that combining the grand-canonical approach with machine learning and ensemble truncation offers an efficient framework for modelling and interpreting NMR spectra in disordered crystalline materials.

Graphitic carbon nitride (gC3N4, or CN herein) is widely studied as a photocatalyst owing to its ease of synthesis, high stability, and optoelectronic properties. However, its photocatalytic performance often remains limited, and a common approach to tune its function and enhance its performance is by doping. Boron (B) functionalization of CN has showed a potential benefit on photocatalytic performance for several reactions. However, the reason for this improvement and the links between synthesis method, exact B chemical environment, and performance remain unclear. Here, we present a fundamental study that elucidates the influence of (i) B functionalization, (ii) B content, and (iii) choice of B precursor on the physicochemical, adsorptive, optoelectronic, and photocatalytic properties of bulk B-CN. We synthesized two sets of B-CN materials (0.5-11 at% B), using either elemental boron or boric acid as precursors. The samples were characterized using several imaging and spectroscopic techniques, which confirm the integration of B into the material through B-O bonding and the creation of B clusters in the case of the boron precursor, with density functional theory (DFT) calculations supporting our analyses. The distribution of B atoms within B-CN particles remained heterogeneous. Compared to CN, B-functionalized materials show enhanced porosity and CO2 uptake, with similar degrees of light absorption and deeper energy band positions. Transient absorption spectroscopy (TAS) measurements showed that charge carrier populations, lifetimes, and kinetics were not significantly affected by B functionalization; however, at 5 at% B doping, an increase in the concentration of charge carriers was seen. Higher B content enhances the photocatalytic NO x removal under UVA irradiation (almost two-fold) and the selectivity to NO3 - from NO x photooxidation, but has no significant effect on CO2 photoreduction, compared to pristine CN. Overall, this study provides fundamental insights to build on and more rationally produce better-performing B-CN photocatalysts.

Zeolite-formation mechanisms have long been the subject of intensive study, with most work concentrating on hydrothermal mechanisms. However, non-traditional zeolite syntheses that do not rely on hydrothermal crystallisation have provided a number of new routes to interesting and unexpected new materials, but their formation mechanisms remain poorly understood. Here, we show how simultaneous in situ liquid- and solid-state 29Si NMR spectroscopy can reveal the mechanism of the formation of a zeolite from a layered silicate precursor. The study provides evidence for the species that are intercalated into the layered material and establishes those that are involved in building the inter-layer, zeolitic connections as a function of time during the zeolite formation process.

Postsynthetic modification of metal-organic frameworks (MOFs) has proven a hugely powerful tool to tune physical properties and introduce functionality, by exploiting reactive sites on both the MOF linkers and their inorganic secondary building units (SBUs), and so has facilitated a wide range of applications. Studies into the reactivity of MOF SBUs have focussed solely on removal of neutral coordinating solvents, or direct exchange of linkers such as carboxylates, despite the prevalence of ancillary charge-balancing oxide and hydroxide ligands found in many SBUs. Herein, we show that the µ2-OH ligands in the MIL-53 topology Sc MOF, GUF-1, are labile, and can be substituted for µ2-OCH3 units through reaction with pore-bound methanol molecules in a very rare example of pressure-induced postsynthetic modification. Using comprehensive solid-state NMR spectroscopic analysis, we show an order of magnitude increase in this cluster anion substitution process after exposing bulk samples suspended in methanol to a pressure of 0.8 GPa in a large volume press. Additionally, single crystals compressed in diamond anvil cells with methanol as the pressure-transmitting medium have enabled full structural characterisation of the process across a range of pressures, leading to a quantitative single-crystal to single-crystal conversion at 4.98 GPa. This unexpected SBU reactivity – in this case chemisorption of methanol – has implications across a range of MOF chemistry, from activation of small molecules for heterogeneous catalysis to chemical stability, and we expect cluster anion substitution to be developed into a highly convenient novel method for modifying the internal pore surface and chemistry of a range of porous materials.

The combination of multinuclear NMR spectroscopy with 17O isotopic enrichment and DFT calculations provided detailed insight into both the bulk and surface structure of γ-Al2O3. Comparison of experimental 17O NMR spectra to computational predictions confirmed that bulk γ-Al2O3 contains Al cations primarily in "spinel-like" sites, with roughly equal numbers of alternating AlVI and AlIV vacancies in disordered "chains". The work showed that overlap of signals from OIV and OIII species complicates detailed spectral analysis and highlighted potential problems with previous work where structural conclusions are based on an unambiguous assignment (and quantification) of these signals. There was no evidence for the presence of H, or for any significant levels of O vacancies, in the bulk structure of γ-Al2O3. Computational predictions from structural models for different surfaces showed a wide variety of protonated and non-protonated O species occur. Assignment of signals for two types of protonated O species was achieved using variable temperature CP and TRAPDOR experiments, with the sharper and broader resonances attributed to more accessible surface sites that interact more strongly with water and less accessible aluminols, respectively. DFT-predicted 1H NMR parameters confirmed the 1H shift increases with denticity but is also dependent on the coordination number of the next nearest neighbour Al species. Spectral assignments were also supported by 1H-27Al RESPDOR experiments, which identified spectral components resulting from μ1, μ2 and μ3 aluminols. Combining these with 1H-27Al D-HMQC experiments showed that (i) μ1 aluminols are more likely to be bound to AlIV, (ii) μ2 aluminols are coordinated to all three types of Al, but with a higher proportion bound to similar types of Al and (iii) μ3 aluminols are most likely bound to higher coordinated Al species. 1H DQ MAS spectroscopy confirmed no aluminols exist exclusively in isolation but showed that the closest proximities are between bridging aluminols coordinated to AlIV and/or AlV species.

This study sheds light on the kinetics of crystallisation of two Zr-based metal-organic frameworks (MOFs), namely Zr6-MOF-808 and Zr6-MOF-801, using in situ powder x-ray diffraction (PXRD). Once a room temperature synthesis for the two MOFs was designed for the very small scale, a successful series of in situ PXRD experiments over the range of 10 degrees C-40 degrees C yielded high quality quantitative information on the kinetics of crystallisation for both MOFs. These findings indicate the importance of the solubility of the linker and its connectivity: while the rate of nucleation and the resulting particle size of the MOF (Zr6-MOF-801), with the less soluble and lower connected linker, was strongly temperature dependent, the growth and particle size of Zr6-MOF-808 was hardly impacted by an increase in temperature. This work highlights the importance of careful preliminary research and helps to improve future MOF synthesis design to efficiently achieve the desired particle size distribution.

Organic materials are increasingly commanding attention as a sustainable choice for charge storage in rechargeable batteries. To fully realise their promise, significantly more understanding is needed in terms of structure-property correlations. Here we report a highly conjugated molecule, disodium anthracene-9,10-carboxylate (Na2ADC), synthesised using rapid microwave-assisted heating and evaluated as an anode material in sodium-ion batteries. Detailed material characterisation is reported, including the crystal structure determined from three-dimensional electron diffraction (3D ED) studies, demonstrating the suitability and advantage of this method for the structural characterisation of organic electrode materials. This study highlights the role of molecular design and structural properties in facilitating the delivery of high-performing organic electrode materials.

Zeolites contain extraframework cations that are exchangeable under favorable aqueous conditions; this is the fundamental feature for their application in water purification and necessary to produce cation forms for other applications such as catalysis. Optimization of the process is common, but there is little fundamental understanding based on real-time experiments of the mechanism of exchange for most zeolites. The sodium and potassium forms of zeolite chabazite selectively uptake Cs+ by ion exchange, leading to its application in removing radioactive Cs-137(+) from industrial nuclear waste streams, as well as from contaminated environments in the aftermath of the Fukushima and Three Mile Island accidents. In this study, in situ synchrotron powder X-ray diffraction patterns have been collected on chabazite as it undergoes Cs-ion exchange. Applying Rietveld refinement to these patterns has revealed the time-resolved structural changes that occur in the zeolite as exchange progresses, charting the changes in the spatial distribution of the extraframework cations and water molecules in the structure during the reaction. Ultimately, a detailed mechanistic understanding of how this dynamic ion-exchange reaction occurs has been obtained.

Microporous AlPO 4 STA-1 has been synthesised and studied by NMR crystallography; it is an effective catalyst for the Beckmann rearrangement of cyclohexanone oxime.

This Faraday Discussion explored the field of NMR crystallography, and considered recent developments in experimental and theoretical approaches, new advances in machine learning and in the generation and handling of large amounts of data. Applications to a wide range of disordered, amorphous and dynamic systems demonstrated the range and quality of information available from this approach and the challenges that are faced in exploiting automation and developing best practice. In these closing remarks I will reflect on the discussions on the current state of the art, questions about what we want from these studies, how accurate we need results to be, how we best generate models for complex materials and what machine learning approaches can offer. These remarks close with thoughts about the future direction of the field, who will be carrying out this type of research, how they might be doing it and what their focus will be, along with likely possible challenges and opportunities.

Living on an increasingly polluted planet, the removal of toxic pollutants such as sulfur dioxide (SO2) from the troposphere and power station flue gas is becoming more and more important. The CPO-27/MOF-74 family of metal-organic frameworks (MOFs) with their high densities of open metal sites is well suited for the selective adsorption of gases that, like SO2, bind well to metals and have been extensively researched both practically and through computer simulations. However, until now, focus has centered upon the binding of SO2 to the open metal sites in this MOF (called chemisorption, where the adsorbent-adsorbate interaction is through a chemical bond). The possibility of physisorption (where the adsorbent-adsorbate interaction is only through weak intermolecular forces) has not been identified experimentally. This work presents an in situ single-crystal X-ray diffraction (scXRD) study that identifies discrete adsorption sites within Ni-MOF-74/Ni-CPO-27, where SO2 is both chemisorbed and physisorbed while also probing competitive adsorption of SO2 of these sites when water is present. Further features of this site have been confirmed by variable SO2 pressure scXRD studies, DFT calculations, and IR studies.

We characterise the solid form of the lichen metabolite, usnic acid, using NMR crystallography to achieve absolute assignment of all observed signals. 13 C NMR spectroscopy shows that usnic acid in wild Usnea lichen has the same crystalline form.

We report the first synthesis of the mixed-metal chabazite-type AlxGa1-xPO4-34(mim) solid solution, containing 1-methylimidazolium, mim, as structure directing agent (SDA), from the parent mixed-metal oxide solid solution, gamma-(AlxGa1-x)2O(3). This hitherto unreported family of materials exhibits complex disorder, arising from the possible distributions of cations over available sites, the orientation of the SDA and the presence of variable amounts of water, which provides a prototype for understanding structural subtleties in nanoporous materials. In the as-made forms of the phosphate frameworks, there are three crystallographically distinct metal sites: two tetrahedral MO4 and one octahedral MO4F2 (M = Al, Ga). A combination of solid-state NMR spectroscopy and periodic DFT calculations reveals that the octahedral site is preferentially occupied by Al and the tetrahedral sites by Ga, leading to a non-random distribution of cations within the framework. Upon calcination to the AlxGa1-xPO4-34 framework, all metal sites are tetrahedral and crystallographically equivalent in the average R3 symmetry. The cation distribution was explored by P-31 solid-state NMR spectroscopy, and it is shown that the non-random distribution demonstrated to exist in the as-made materials would be expected to give remarkably similar patterns of peak intensities to a random distribution owing to the change in average symmetry in the calcined materials.

Sodium-ion batteries are emerging as a sustainable solution to tackle the growing global energy demands. In this context, organic electrode materials complement such technologies as they are composed of earth-abundant elements. As organic anodes, sodium carboxylates exhibit promising applicability in a wide range of molecules. To harness the advantages of individual systems and to minimise their limitations, in this work, an approach to form binary mixtures of sodium carboxylates using one-pot, microwave-assisted synthesis is presented. The target mixtures were synthesised in 30 min with disodium naphthalene-2,6-dicarboxylate (Na-NDC) as a common constituent in all. Both components in all mixtures were shown to participate in the charge storage and had a considerable effect on the performance characteristics, such as specific capacity and working voltage, in half and full cell formats. This approach opens a new avenue for enabling organic materials to be considered as more competitive candidates in sodium-ion batteries and promote their use in other material classes to overcome their limitations.

The sodium ion conductor Na3PS4 is a promising electrolyte for future all-solid-state batteries using Na+ ions as ionic charge carriers. Its readily available components make it a compelling and more sustainable alternative to recent Li-ion technologies. At ambient temperature, the ionic conductivity is in the order of 10(-4) S cm(-1), which can be optimized by adjusting doping and processing parameters. Even though several studies have focused on explaining the dynamic properties of doped and undoped Na3PS4, the driving forces that lead to fast Na+ exchange are not yet completely understood. Here, we synthesized nanocrystalline, defect-rich cubic Na3PS4 via a solid-state synthesis route and compared its properties with those of highly crystalline Ca-doped Na3-2xCaxPS4. The interconnected effects of doping and synthesis procedure on both structure and dynamic properties are investigated. X-ray diffraction reveals that the undoped samples show clear cubic and tetragonal symmetry, while for the doped samples, a phase mixture of both polymorphs is seen. High-resolution Na-23 magic angle spinning NMR spectra acquired at temperatures as low as -60 degrees C clearly reveal two different Na sites when ionic motion is partially frozen out. Ion dynamics of the powder samples were analyzed using high-precision broadband impedance spectroscopy and variable-temperature, time-domain Na-23 NMR spin-lattice relaxation rate measurements. Localized Na+ jumps detected by NMR showed higher energy barriers but faster Na+ dynamics for the Ca-doped samples. A similar trend was observed in conductivity spectroscopy with lowest activation energy for Na-ion transport in tetragonal Na3PS4 but highest attempt frequencies for the hopping motion in Ca-doped Na3PS4 with x = 0.135, making the doped sample the superior ion conductor at elevated temperatures. Our study highlights the importance of breaking down ionic transport in its elemental steps to understand the complex interplay of intrinsic and extrinsic parameters in solid electrolyte materials.

The assembly–disassembly–organization–reassembly (ADOR) process for the transformation of zeolite UTL using water has been studied by using 29Si and 17O solid-state NMR spectroscopy. The results show that the intermediate materials that are formed during the reaction are extremely dynamic and that the process involves both irreversible changes in structure that define the overall pathway and reversible lability of the Si–O–Si linkages that have no effect on the overall structure. The combination of processes occurring during the ADOR reaction means that the mechanism is considerably more complex than initially proposed.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Application of pressure induces reactivity of pore-bound methanol with the secondary building unit of the metal–organic framework GUF-1(Sc), substituting coordinated bridging hydroxide ligands for bridging methoxides, in single crystals and in bulk.