25 Years of Reticular Chemistry Freund, Ralph; Canossa, Stefano; Cohen, Seth M. ...
Angewandte Chemie (International ed.),
November 2, 2021, Volume:
60, Issue:
45
Journal Article
Peer reviewed
Open access
At its core, reticular chemistry has translated the precision and expertise of organic and inorganic synthesis to the solid state. While initial excitement over metal–organic frameworks (MOFs) and ...covalent organic frameworks (COFs) was undoubtedly fueled by their unprecedented porosity and surface areas, the most profound scientific innovation of the field has been the elaboration of design strategies for the synthesis of extended crystalline solids through strong directional bonds. In this contribution we highlight the different classes of reticular materials that have been developed, how these frameworks can be functionalized, and how complexity can be introduced into their backbones. Finally, we show how the structural control over these materials is being extended from the molecular scale to their crystal morphology and shape on the nanoscale, all the way to their shaping on the bulk scale.
Reticular chemistry translates the precision and expertise of organic and inorganic synthesis to the solid state. The most profound innovation of the field has been the elaboration of design strategies for the synthesis of extended crystalline solids through strong directional bonds. This Review highlights the classes of reticular materials, their functionalization, and the introduction of complexity into their backbones.
The two-dimensional population balance model (2D PBM) introduces the enhanced capability of modeling two different sets of growth kinetics, which can offer advantages to modeling crystallization ...processes that generate needle-like particles, a commonly encountered active pharmaceutical ingredient (API) morphology. Although one-dimensional population balance model (1D PBM) can be utilized effectively to model nonequant morphologies with the selection of appropriate shape factors, it cannot account for morphology or aspect ratio changes that can occur during the crystallization process. In this work, the advantage of the 2D PBM for an industrial crystallization process that generates needle-shaped API is highlighted by comparing the 1D PBM and 2D PBM results. The API utilized for this work had extremely slow desupersaturation and was not able to achieve solubility concentration despite an ∼50 h seed bed age. While the 1D PBM is useful in optimizing the crystallization process to enhance desupersaturation behavior, the 1D PBM did not match the particle size quantiles and, thus, could not be utilized to probe the impact of crystallization process parameters on the particle aspect ratio (AR). The 2D PBM was necessary to model the particle size quantiles and was utilized to further optimize process conditions for minimizing the particle aspect ratio. Simulations utilizing the 2D PBM indicated that, regardless of antisolvent addition rate or seed morphology, the final material would still have a high aspect ratio. This knowledge saved the investment of much time and effort in trying to minimize particle AR with changes in crystallization processing parameters alone and, thus, highlights the utility of the 2D PBM to the pharmaceutical industry.
Elevated temperature and pressure conditions in sub-/supercritical water environments hinder the direct observation of salt crystallization phenomena, resulting in indeterminate salt crystal ...morphologies. In this study, an innovative experimental apparatus has been developed to conduct in situ investigations into the crystal morphology of various types of inorganic salts. The results indicate that the critical temperature of the water-salt system is higher than that of pure water systems, with phase transition thresholds for saturated NaCl-H2O and KCl-H2O systems 671.4 K and 728.1 K, respectively. A distinct “flash crystallization” phenomenon is observed during the crystallization of inorganic salts, accompanied by different crystal morphologies. KCl crystals exhibit a dispersed particle form, NaCl crystals manifest in a finely fragmented accumulation form, and Na2SO4 crystals present transparent feather-like structures. The size of NaCl crystals formed on the surface of a Ni wire at 622.8 K through heterogeneous nucleation ranges from 200.4 μm to 450.9 μm. The crystallization characteristics of salt in sub-/supercritical water are influenced by various factors, including electric dipole moment interactions, common ion effect, the effect of type I salts on type II salts, and homo/heterogeneous nucleation.
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•Salt crystallization processes in sub-/supercritical water environments are observed in situ.•The critical temperature of the water-salt system exceeds that of pure water systems.•Transparent feather-like structures characterize Na2SO4 crystals in supercritical water.•NaCl crystal size on nickel wire surfaces varies from 200.4 μm to 450.9 μm.
The precursor was treated by KMnO4 and combined with the formation of single crystal primary particles to improve the electrochemical performance of LiNi0.8Mn0.1Co0.1O2 in this study. The single ...crystal primary morphology of the cathode material can not only shorten the migration path of lithium ions, but also maintain the integrity of particle morphology and avoid the generation of cracks in particles after circulation. Some Mn4+ from KMnO4 incorporated into the crystal lattice, causing a small amount of Ni2+ act as pillars in the lithium layer and thus avoiding its collapse in the delithium state. Besides that, a thin MnO2 layer is also formed on the cathode material, which inhibit side reactions between electrolyte and cathode material. The results show that the synergistic coupling effects of single crystal morphology and precursor treatment are realized to improve the electrochemical properties of the Ni-rich cathode materials.
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•MnO2 layer improves interface stability between cathode material and electrolyte.•The side decomposition of LiPF6 and electrolyte has been suppressed.•Mn-doped into the cathode material triggers partial Ni3+ reduction to Ni2+.•Ni2+ migrate to lithium layer which prevent interslab collapse during cycling.•The single crystal morphology inhibits the generation of cracks during cycling.
•The negative effect of hot spots in microwave field on MOFs synthesis was analyzed.•The regulation of hot spots occurring was investigated by numerical simulation.•Several synthetic strategies were ...proposed to weaken hot spots.•Regular and uniform particles of MOFs were obtained by employing the strategies.
Microwave (MW) irradiation is known to enable facile synthesis of MOFs. However, the complex distribution of MW field causes the generation of hot spots in the MW reactor; this phenomenon causes local overheating that is unfavorable for the nucleation and growth of MOFs crystals. The present study uses numerical simulation to achieve rational design of MW-assisted synthesis by eliminating hot spots. First, we evaluate the influence of hot spots by analyzing the morphology of MIL-88B (Fe) synthesized in the presence and absence of hot spots, respectively. SEM images show that nearly 50% of the hexagonal bipyramidal-shaped particles deteriorate into irregular shapes in the presence of hot spots, revealing the detrimental effect of overheating phenomenon on the synthesis of MOFs. Then, the regulation of hot spots occurring is investigated by simulating the temperature distribution in the reactant solution under various operating parameters, including the input power, the shape and dimension of cavities, the dielectric property of reactants, as well as the stirring rate. Based on the simulating results, several strategies are proposed to weaken hot spots, including the adjustment of MW power, the optimization of cavity structure and the enhancement of liquid turbulence. The simulating results show that these strategies eliminate hot spots and equalize liquid temperature in the solution. Moreover, the effect of these strategies is validated experimentally, where the regular and uniform particles are obtained when these strategies are employed. The present study can provide guidance for the further design of MW-assisted reactor for materials synthesis.
•Symmetry breaking by the seed crystals can redirect growth toward hierarchy.•Branching may be triggered by the intrinsic electronic properties of nanoparticles.•Hierarchy can develop through coupled ...interfacial nucleation and assembly.
The development of structural hierarchy on various length scales during crystallization process is ubiquitous in biological systems and is also observed in synthetic nanomaterials. The driving forces for the formations of complex architectures range from local interfacial interactions, that modify interfacial speciation, local supersaturation, and nucleation barriers, to macroscopic interparticle forces. Although it is enticing to interpret the formation of hierarchical architectures as the assembly of independently nucleated building blocks, often crystallization pathways follow monomer-by-monomer addition with structural complexity arising from interfacial chemical coupling and strongly correlated fluctuation dynamics in the electric double layers. Here, the mechanism of the development of structural hierarchy through heterogeneous nucleation, coupled interfacial nucleation and assembly, and oriented attachment of independently nucleated particles is discussed. The emphasis is made on the discussion of the underlying interfacial forces and chemical coupling that drives crystallization pathways towards the formation of structural hierarchy.
Semicrystalline polymers products usually adopt a crystallized form in their end-use environment. These crystallized polymers undergo various deformations under different external fields (e.g., ...stretching) from precursor processing, post treatment to final shape formation. Such deformation process is accompanied by multi-scale and multi-stage structural evolutions due to the complex hierarchical structures of crystallized polymers. These structural evolutions control over essential physical properties of semicrystalline polymers, which can be further developed towards high-performance industrial materials. A profound understanding of associated mechanisms is the critical key to interpret the complicated deformation process and to optimize the practical performances of polymer materials. The past reviews have more or less focused on one aspect of deformation while the multi-scale vision is lacking. Herein, this review brings a comprehensive presentation of strain-induced structural mechanics of crystallized polymers based on a multi-scale, multi-stage standpoint from the initiation of plasticity until failure. Important structural changes and associated mechanisms during the whole deformation process are systematically summarized, with particular attention paid to the crystal phase transition and crystal morphology evolution. Besides, the relationships between resulted microstructures and the essential end-use properties of crystallized polymers as well as their performances as common industrial materials are discussed. By summarizing the recent processes, this review is hoped to open up more aventunes for developing deformation-inspired sophisticated materials facing broader and interdisciplinary application fields.
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Layered metal-organic frameworks would be a diverse source of crystalline sheets with nanometer thickness for molecular sieving if they could be exfoliated, but there is a challenge in retaining the ...morphological and structural integrity. We report the preparation of 1-nanometer-thick sheets with large lateral area and high crystallinity from layered MOFs. They are used as building blocks for ultrathin molecular sieve membranes, which achieve hydrogen gas (H2) permeance of up to several thousand gas permeation units (GPUs) with H2/CO2 selectivity greater than 200. We found an unusual proportional relationship between H2 permeance and H2 selectivity for the membranes, and achieved a simultaneous increase in both permeance and selectivity by suppressing lamellar stacking of the nanosheets.
Organic compounds, often used in cement systems as admixtures, may affect the crystallisation and carbonation kinetics of Ca(OH)2, an important phase of hydrated cement. Here, we investigated changes ...in Ca(OH)2 morphology in the presence of 3 organic compounds, commonly encountered in cement and lime-based materials: sucrose, pectin and calcium lignosulfonate. The additives were introduced either before or after lime slaking to determine the influence of temperature. Ca(OH)2 crystals and supernatant solutions were characterised at time of slaking and after 6 months of ageing using scanning electron microscopy, X-ray diffraction and optical emission spectroscopy.
Our results indicate that the morphology of Ca(OH)2 crystals is modified by the characteristics of the organic molecules which promote formation of Ca(OH)2 with habits that can result in faster carbonation, an effect that is detrimental to cement used in reinforced concrete. These effects are enhanced when the additives are introduced before slaking, likely as a result of thermal degradation.
•Sucrose and lignosulfonate reduce the crystallite size of Ca(OH)2.•Lime slaking in sucrose solutions leads to Ca(OH)2 with irregular shape.•Lime slaking in presence of lignosulfonate leads to plate-like Ca(OH)2 crystals.•Effects of additives are enhanced when introduced before slaking.•Additives stabilise the unstable edge faces of Ca(OH)2 during ageing.
The study of crystal growth and regeneration mechanisms is of great significance for controlling the morphology of crystals. Through the investigation of the recovery and regrowth processes of ...crystals, we have revealed the regeneration mechanism of aceclofenac (ACF) crystals and the influence of hydroxypropyl methylcellulose (HPMC) on the regeneration of ACF crystals. Firstly, ACF crystal regeneration experiments were conducted in acetone (ACT) and methyl acetate (MA), and it was found that the broken crystals could be successfully regenerated and restored to their original morphology, the regenerated ACF crystals in MA exhibited a larger aspect ratio. Secondly, the crystals obtained from the two solvents were placed in different solvents for regrowth, and it was shown that solvent was a key factor influencing the aspect ratio of ACF crystals. Additionally, HPMC was used to regulate the crystal morphology, it was found that the best effect was achieved when the mass fraction of HPMC was 0.5%, resulting in a regenerated crystal with an aspect ratio of only 2.19. Molecular simulation results indicated that the interaction between the radial (110) crystal facet and the solvent was weaker than that with the axial (1 0 -1) crystal facet, leading to a higher radial growth rate and a larger aspect ratio of the crystal. However, after adding HPMC, the interaction between HPMC and the radial (1 1 -1) and (110) crystal facets became stronger. HPMC selectively adsorbed on these two crystal facets, ultimately resulting in crystals with a smaller aspect ratio. The research findings of this study will provide theoretical basis for solving the problem of difficult morphology control due to crystal fragmentation in the pharmaceutical industry production process.
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