Bone mineral forms both inside and between collagen fibrils in the extracellular matrix. While the morphology of intrafibrillar bone mineral has been hypothesized to be primarily controlled by the size and shape of the restricted spaces inside collagen fibrils within which the mineral forms, what controls the architecture of the extrafibrillar mineral is still an open question. While bone mineral is primarily apatitic in composition, it also contains significant quantities of cell respiration metabolites, in particular, carbonate, citrate, and lactate. An as-yet unanswered question is what, if any, role do these metabolites collectively play in determining the 3D architecture of bone mineral. Here, we propose a composite model of bone mineral that accounts for both intra- and extrafibrillar mineral environments, and to that end, we develop apatitic materials containing citrate and lactate or carbonate that mimic the densely packed ionic environments within which bone mineral forms in vivo. We find that incorporating citrate and lactate leads to complex mineral architectures reminiscent of those in extrafibrillar bone mineral, including mineral crystal curvature. Our results suggest that metabolic acids may play an important role in building the 3D architecture of extrafibrillar bone mineral.

In this contribution we present for the first time an operando study of mechanochemical syntheses relying on Nuclear Quadrupole Resonance spectroscopy (NQR). This method represents, to date, the best functional alternative to NMR spectroscopy for the real-time monitoring of ball-milling (BM) syntheses. Two mechanochemical syntheses were followed in operando mode by NQR, namely the formation of a halogen-bonded co-crystal and the preparation of a hybrid perovskite, demonstrating potential applications of this novel technique, as well as its complementarity to more conventional operando methods used in mechanochemistry. Lastly, we show that our BM-NQR set-up can also be used in real-time to follow the temperature evolution directly inside the milling jar.

In this contribution, we apply our newly developed ball-milling operando platform, which combines Raman spectroscopy and thermal (IR) imaging, as well as acoustic and high-speed optical video recordings, to the synthesis and transformation of citric acid-isonicotinamide (1:2) cocrystal polymorphs in transparent PMMA jars. Particularly, we demonstrate how Raman, temperature, acoustic, and video data are complementary and enable detection and connection of chemical and physical events happening during ball-milling in a time-resolved manner. Importantly, we show that the formation of the three cocrystal polymorphs can be detected through acoustic analyses solely. Even more impressively, the meticulous analyses of the sound data allowed subtle polymorphic transitions to be perceived in operando mode when the Raman spectroscopy was not conclusive enough. Such changes in sound signatures are greatly linked to the beads' motions in the milling jar. A new data analysis methodology of acoustic recordings is proposed through a combination of energetic and statistical approaches that simplifies the data analyses for potential users. The interpretation of the detected sound signals was further validated thanks to the high-speed videos recorded in synchronization with all other operando techniques. Finally, we broaden this acoustic methodology to opaque stainless-steel jars, showing the relevance of the acoustic analysis method for following polymorphic transformations of cocrystals, as well as pure substances, in any type of milling jar.

The importance of (bi)carbonate salts cannot be understated. They are vital to the Earth's geology and ecosystems and are used as precursors by chemists for the synthesis of functional materials. Naturally, solid-state NMR (ssNMR) appears as the spectroscopic tool of choice to probe the atomic-level structure and dynamics of (bi)carbonate salts. Of the possible nuclei available as spectroscopic probes in carbonate and bicarbonate ions (i.e., 1H, 13C, and 17O), oxygen-17 is highly attractive. Yet, it is seldom employed, largely due to its low natural abundance (0.04 %) and lack of practical enrichment protocols. Recently, we reported an effective 17O-labeling strategy involving mechanochemistry of Na2CO3·H2O, Na2CO3, NaHCO3, K2CO3·1.5H2O, and KHCO3, and recorded their 17O NMR spectral fingerprints near room temperature. In this work, ultra-low temperature (i.e., 100 K) 17O ssNMR spectra of these phases are acquired at two magnetic fields, 14.1 and 18.8 T, to extract the 17O NMR parameters δiso, CQ, and ηQ for the different oxygen sites, and to further study the influence of dynamics on the spectra. We compare the experimental 17O NMR parameters to those computed with GIPAW-DFT calculations both on static models, and after averaging by molecular dynamics (MD) simulations. This approach was taken to aid in analyzing the structure-spectra relationships and shed light on the dynamics. Lastly, we report the static GIPAW-DFT calculations of 17O NMR parameters for a series of other carbonate salts of interest, further expanding upon current experimental 17O ssNMR results.

Correction for ‘Capturing and labeling CO 2 in a jar: mechanochemical 17 O-enrichment and ssNMR study of sodium and potassium (bi)carbonate salts’ by Austin Peach et al. , Chem. Sci. , 2025, 16 , 10731–10741, https://doi.org/10.1039/D4SC08491H.

With the rapid increase in temperatures around the planet, the need to develop efficient means to reduce CO2 emissions has become one of the greatest challenges of the scientific community. Many different strategies are being studied worldwide, one of which consists of trapping the gas in porous materials, either for its short- or long-term capture and storage, or its re-use for the production of value-added compounds. Yet, to further the development of such systems, there is a real need to fully understand their structure and properties, including at the molecular-level following the physisorption and/or chemisorption of CO2 (which can lead to various species, including carbonate and bicarbonate ions). In this context, 17O NMR naturally appears as the analytical tool of choice, because of its exquisite sensitivity to probe subtle differences in oxygen bonding environments. To date, it has scarcely been used, due to the very low natural abundance of 17O (0.04%), and the difficulty in purchasing or obtaining commercial 17O-labeled compounds adapted to such investigations (e.g., 17O-CO2(g), or 17O-enriched Na- and K-(bi)carbonate salts, which can be readily transformed into CO2). Herein, we demonstrate how, using mechanochemistry, it is possible to enrich with 17O a variety of Na- and K-(bi)carbonate salts in a fast, economical, scalable, and user-friendly way. The high enrichment levels enabled recording the first high-resolution 17O ssNMR spectra of these phases at different temperatures and magnetic fields. From these, the typical spectral signatures of (bi)carbonate ions could be obtained, showing their strong sensitivity to local environments and dynamics. Lastly, we show how thanks to the selective 17O-labeling, other aspects of the reactivity of carbonates in materials can be unveiled using in situ 17O ssNMR. In the long run, it is expected that this work will open the way to more profound investigations of the structure and properties of carbon capture and storage systems, and, more generally speaking, of functional materials containing carbonates.

In this contribution, we apply our newly developed ball-milling operando platform, which combines Raman spectroscopy, thermal (IR) imaging, as well as acoustic and high-speed optical video recordings, to the synthesis and transformation of citric acid – isonicotinamide (1 : 2) cocrystal polymorphs. Particularly, we demonstrate how Raman, temperature, acoustic and video data are complementary and enable to detect and connect together chemical and physical events happening during the ball-milling in a time-resolved manner. Importantly, we show that the formation of the three polymorphs can be detected through the acoustic analyses solely. Even more impressively, the meticulous analyses of the sound data allowed the subtle polymorphic transitions to be perceived in operando mode when the Raman spectroscopy was not conclusive enough. Such changes in sound signatures are greatly linked to the beads’ motions in the milling jar. A new data analysis methodology of acoustic recordings is proposed through a combination of energetical and statistical approaches, which simplifies the data analyses for potential users. The interpretation of the detected sound signals was further validated thanks to the high-speed videos recorded in synchronization with all other operando techniques. Finally, we broaden this acoustic methodology to opaque stainless-steel jars, showing the relevance of the acoustic analysis method for any type of milling jars.

Octacalcium phosphate (OCP, Ca8(PO4)4(HPO4)2.5H2O) is a notable calcium phosphate due to its biocompatibility, making it a widely studied material for bone substitution. It is known to be a precursor of bone mineral, but its role in biomineralisation remains unclear. While the structure of OCP has been the subject of thorough investigations (including using Rietveld refinements of X-ray diffraction data, and NMR crystallography studies), important questions regarding the symmetry and H-bonding network in the material remain. In this study, it is shown that OCP undergoes a lowering of symmetry below 200 K, evidenced by 1H, 17O, 31P and 43Ca solid state NMR experiments. Using ab-initio molecular dynamics (MD) simulations and Gauge Including Projected Augmented Wave (GIPAW) DFT calculations of NMR parameters, the presence of rapid motions of the water molecules in the crystal cell at room temperature is proved. This information leads to an improved description of the OCP structure at both low and ambient temperatures, and helps explain long-standing issues of symmetry. Remaining challenges related to the understanding of the structure of OCP are then discussed.

The Zr-based Metal Organic Framework (MOF) UiO-66(Zr) is widely employed owing to its good thermal and chemical stabilities. Although the long-range structure of this MOF is preserved in the presence of water during several days, little is known about the formation of defects, which cannot be detected using diffraction techniques. We apply here O-17 solid-state NMR spectroscopy at 18.8 T to investigate the reactivity of UiO-66, through the exchange of oxygen atoms between the different sites of the MOF and water. For that purpose, we have selectively enriched in O-17 isotope the carboxylate groups of UiO-66(Zr) by using it with O-17-labeled terephthalic acid prepared using mechanochemistry. In the presence of water at 50 degrees C and a following dehydration at 150 degrees C, we observe an overall exchange of O atoms between COO- and mu(3)-O2- sites. Furthermore, we demonstrate that the three distinct oxygen sites, mu(3)-OH, mu(3)-O2- and COO-, of UiO-66(Zr) MOF can be enriched in O-17 isotope by post-synthetic hydrothermal treatment in the presence of O-17-enriched water. These results demonstrate the lability of Zr-O bonds and the reactivity of UiO-66(Zr) with water.

Oxalate ligands are found in many classes of materials, including energy-storage materials and biominerals like hydrated calcium-oxalates. Determining their local environments at the atomic scale is thus paramount to establishing the structure and properties of numerous phases. Here, we show that high-resolution 17O solid-state NMR is a valuable asset for investigating the structure of crystalline oxalate systems. First, an efficient 17O-enrichment procedure of oxalate ligands is demonstrated using mechanochemical saponification. Then, the use of 17O-enriched oxalates for the synthesis of the biologically relevant calcium-oxalate monohydrate (COM) phase is presented, enabling the analysis of its structure and heat-induced phase transitions by high-resolution 17O solid-state NMR. NMR studies of the low-temperature COM form (LT-COM), using magnetic fields varying from 9.4 to 35.2 T, as well as 13C-17O MQ/D-RINEPT and 17O{1H} MQ/REDOR experiments, enabled the 8 inequivalent oxygen sites of the oxalate ligands to be resolved, with a tentative assignment proposed. Then, the structural changes occurring upon heat treatment of COM were followed by high-resolution 17O solid-state NMR, providing new insight into the structures of the high-temperature form (HT-COM) and anhydrous calcium oxalate alpha-phase (alpha-COA), including the presence of structural disorder in the latter case. Overall, this work highlights the ease associated with 17O-isotopic enrichment of oxalate oxygens, and how it enables the study of oxalate structures (including materials of biological relevance) at high-resolution via solid-state NMR, in the frame of “NMR-crystallography” investigations.

While ball-milling is becoming one of the common tools used by synthetic chemists, an increasing number of studies highlight that it is possible to further expand the nature and number of products which can be synthesized, by heating the reaction media during mechanochemical reactions. Hence, developing set-ups enabling heating and milling to be combined is an important target, which has been looked into in both academic and industrial laboratories. Here, we report a new approach for heating up reaction media during ball-milling reactions, using induction heating (referred to as i-BM). Our set-up is attractive not only because it enables a very fast heating of the milling medium (reaching ≈80 °C in just 15 s), and that it is directly adaptable to commercially-available milling equipment, but also because it enables heating either the walls of the milling jars or the beads themselves, depending on the choice of the materials which compose them. Importantly, the possibility to heat a milling medium "from the inside" (when using for example a PMMA jar and stainless steel beads) is a unique feature compared to previously proposed systems. Through numerical simulations, we then show that it is possible to finely tune the properties of this heating system (e.g. heating rate and maximum temperature reached), by playing with the characteristics of the milling system and/or the induction heating conditions used. Lastly, examples of applications of i-BM are given, showing how it can be used to help elucidate reaction mechanisms in ball-milling, to synthesize new molecules, and to control the physical nature of milling media.

17O NMR spectroscopy is a powerful analytical technique, which enables to access unique information regarding the structure and reactivity of biomolecules, such as peptides and proteins. However, due to the exceedingly low natural abundance of 17O (0.04 %), it is necessary to work with 17O-enriched samples, which are not easily accessible because of the experimental constraints and high costs associated with the traditional enrichment procedures. Here, we present simple, fast and cost-efficient labeling strategies for 17O-enrichment of amino acids and peptides. First, using mechanochemical saponification, a variety of unprotected amino acids were enriched within 30 min of milling under ambient conditions, consuming only microliter amounts of costly labeled water, and producing pure molecules with high enrichment levels (up to ~ 40 %), and in medium to high yields (~ 60 - 85 %) without the loss of their optical purity (ee > 99%). The labeling efficiency of the mechanochemical protocol was then compared to a re-optimised enrichment strategy based on acid-catalysed oxygen exchange. Subsequently, 17O-enriched Fmoc/tBu-protected amino acids were produced on a 1 g/day scale with high enrichment levels (~ 40 %), and in high synthetic yields (~ 75 - 85 %), by scaling up the mechanochemical enrichment followed by a Fmoc-protection step. Lastly, a direct site-selective 17O-labeling of carboxylic functions in peptide side-chains was developed and applied to the RGD and GRGDS peptides, reaching up to 29% enrichment level. Producing highly enriched molecules enabled to record 17O solid-state NMR spectra at 14.1 T in reasonable analytical times. Overall, this work represents an important step forward in providing easy access to highly 17O-enriched peptides and proteins to be subsequently studied by high-resolution 17O NMR spectroscopy.

The possibility of enriching in 17O the water molecules within hydrated biominerals belonging to the Ca-pyrophosphate family was investigated, using liquid assisted grinding (LAG) in the presence of 17O-labelled water. Two phases with different hydration levels, namely triclinic calcium pyrophosphate dihydrate (Ca2P2O7·2H2O, denoted t-CPPD) and monoclinic calcium pyrophosphate tetrahydrate (Ca2P2O7·4H2O, denoted m-CPPT β) were enriched in 17O using a "post-enrichment" strategy, in which the non-labelled precursors were ground under gentle milling conditions in the presence of stoichiometric quantities of 17O-enriched water (introduced here in very small volumes ∼10 μL). Using high-resolution 17O solid-state NMR (ssNMR) analyses at multiple magnetic fields, and dynamic nuclear polarisation (DNP)-enhanced 17O NMR, it was possible to show that the labelled water molecules are mainly located at the core of the crystal structures, but that they can enter the lattice in different ways, namely by dissolution/recrystallisation or by diffusion. Overall, this work sheds light on the importance of high-resolution 17O NMR to help decipher the different roles that water can play as a liquid-assisted grinding agent and as a reagent for 17O-isotopic enrichment.

While the research fields of mechanochemistry and solid state NMR (ssNMR) have been developing in independent ways for many years, there are an increasing number of studies in which both topics meet. On one hand, ssNMR can be used to perform advanced characterizations of the structure, morphology and also properties of materials prepared by mechanochemistry. On the other, syntheses performed using mechanochemistry can help push forward the current frontiers of solid state NMR, for example through the development of new phases enriched in NMR-active isotopes. Lastly, studies at the interface between mechanochemistry and ssNMR are increasingly being carried out, notably to help elucidate reaction mechanisms in ball-milling (BM). In this chapter, illustrations of investigations along these lines will be provided, focusing on the synthesis and characterization of materials with an inorganic component, such as oxides, metal-organic frameworks, and zeolites, just to name a few.

Adam B. Braunschweig opened discussion of the paper by Jeung Gon Kim: Regarding the polymers, I am curious about polydispersity at early times/initiation – how fast is this compared to propagation? How uniform are the polymers at early times. Also, anionic polymerization has extreme oxygen and

A simple and versatile preparation of Zn(II)-poly(carboxylates) reticulated binders by the addition of Zn(II) precursors (ZnSO4, ZnO, or Zn(NO3)2) into a preoptimized poly(carboxylic acids) binder solution is proposed. These binders lead systematically to a significantly improved electrochemical performance when used for the formulation of silicon-based negative electrodes. The formation of carboxylate-Zn(II) coordination bonds formation is investigated by rheology and FTIR and NMR spectroscopies. Mechanical characterizations reveal that the coordinated binder offers a better electrode coating cohesion and adhesion to the current collector, as well as higher hardness and elastic modulus, which are even preserved in the presence of a carbonate solvent (i.e., in battery operation conditions). Ultimately, as shown from operando dilatometry experiments, the electrode expansion during lithiation is reduced, mitigating electrode mechanical failure. Such coordinatively reticulated electrodes outperform their uncoordinated counterparts with an improved capacity retention of over 30% after 60 cycles.

Thiophene, a key building block for the construction of conjugated materials, has been scarcely studied in halogen bonding (XB)-driven self-assemblies. In the present study, two thiophene derivatives modified at position 3 were (co-)crystallized using complementary XB donor/acceptor functional groups. Single-crystal X-ray diffraction analysis confirmed the presence of halogen and chalcogen bonding acting, in most cases, concomitantly. While the majority of the structures are governed by the conventional N···I motif, additional S···N and S···S contacts encouraged the cohesion of the supramolecular architectures. Density functional theory calculations shed the light on interaction energy, their respective contributions of the motifs to these non-covalent bonds, and the overall stability of these assemblies. To gain further insight into the formation and evidence of XB interactions, solution and mechanochemical syntheses of polymorphic adducts were performed, followed by 13C solid-state NMR analysis. Further, 1H and 19F{1H} solution-state NMR spectroscopy studies were carried out to highlight these interactions in the solution phase. The strength and directionality of halogen bonding thus reaffirm its role as a structure-directing agent for designing functional materials. The evidence of N···S chalcogen bonds in thiophene derivatives also broadens up the horizon of supramolecular chemistry in S-heterocycles, while necessitating further investigation for rational application in materials science.