The spin-crossover phenomenon (SCO) is a fascinating field that potentially concerns any material containing a (d4–d7) transition metal complex finding therefore an echo in as diverse research fields as chemistry, physics, biology and geology. Particularly, molecular and coordination-polymers SCO solids are thoroughly investigated since their bistability promises new routes towards a large panel of potential applications including smart pigments, optical switches or memory devices. Notwithstanding these motivating applicative targets, numerous fundamental aspects of SCO are still debated. Among them, the investigation of the structure–property relationships is unfailingly at the heart of the SCO research field. All the facets of the richness of the structural behaviors shown by SCO compounds are only revealed when exploring the whole sample scales – from atomic to macroscopic – all the external stimuli – temperature, pressure, light and any combinations and derived perturbations – and the various forms of the SCO compounds in the solid state – crystalline powders, single-crystals, poorly crystalline or nano-sized particles. Crystallography allows investigating all these aspects of SCO solids. In the past few years, crystallography has certainly been in a significant phase of development pushing the frontiers of investigations, in particular thanks to the progress in X-ray diffraction techniques. The encounter between SCO materials and crystallography is captivating, taking advantages from each other. In this paper, a personal account mainly based on our recent results provides perspectives and new approaches that should be developed in the investigation of SCO materials.

Crystallography and spin-crossover. A view of breathing materials.

Hydrothermal and solvothermal syntheses are important branches of inorganic synthesis. Hydrothermal and solvothermal techniques are not just confined to the syntheses and growth of conventional and advanced materials but also take a very broad shape, covering several interdisciplinary branches of science and widely applied in the fields of the treatment of wastes, mimicking geothermal and biohydrothermal processes. In this chapter, we introduce the foundation of hydrothermal and solvothermal syntheses, and we describe the hydrothermal synthesis of some new materials including single crystals materials, zeolites and related microporous materials, ionic conductors, complex oxides and fluorides, inorganic–organic hybrid materials, and nanomaterials. Hydrothermal biochemistry, supercritical water oxidation process, hydrothermal technique and methods, and ionothermal synthesis are also discussed.

Chapter 4 – Hydrothermal and Solvothermal Syntheses

Publisher Summary This chapter focuses on the foundation of hydrothermal and solvothermal syntheses of materials, hydrothermal biochemistry, supercritical water oxidation process, technique and methods, and ionothermal synthesis. Hydrothermal and solvothermal syntheses are important branches of inorganic synthesis. Hydrothermal synthesis refers to the synthesis through chemical reactions in aqueous solution above boiling point of water and solvothermal synthesis in nonaqueous solution at relatively high temperatures. The development of hydrothermal and solvothermal techniques has a history, beginning with the synthesis of minerals and the extraction of elements from minerals. Nowadays, these techniques have widely been applied in the syntheses of conventional and advanced materials, treatment of wastes, and mimicking geothermal and bioehydrothermal processes. Zeolite and quartz industries further promote the basic studies of hydrothermal and solvothermal chemistry, and more and more scientists realize the importance of developing hydrothermal and solvothermal reactions, upon which effective syntheses would be established.

Hydrothermal and Solvothermal Syntheses

We investigated the adsorption performance of five Fe-based MOFs (Fe-BTC, MIL-100(Fe), MIL-101(Fe), MIL-53(Fe) and MIL-88C(Fe)) for removal of antimonite (Sb(III)) and antimonate (Sb(V)) from water. Among these MOFs, MIL-101(Fe) exhibited the best adsorption capacities for both Sb(III) and Sb(V) (151.8 and 472.8 mg/g, respectively) which were higher than those of most adsorbents previously reported. The effect of steric hindrance was evident during Sb removal using the Fe-based MOFs, and the proper diameter of the smallest cage windows/channels should be considered an important parameter during the evaluation and selection of MOFs. Additionally, the adsorption capacities of MIL-101(Fe) for Sb(V) decreased with increasing initial pH values (from 3.0 to 8.0), while the opposite trend was observed for Sb(III). Chloride, nitrate and sulfate ions had a negligible influence on Sb(V) adsorption, while NO3− and SO42− improved Sb(III) adsorption. This result implies that inner sphere complexes might form during both Sb(III) and Sb(V) adsorption.

Removal of antimonite and antimonate from water using Fe-based metal-organic frameworks: The relationship between framework structure and adsorption performance.

Thermal spin-crossover with a large hysteresis spanning room temperature in a mononuclear complex

A new potassium phosphatoantimonate was hydrothermally synthesized and characterized by means of powder X-ray diffraction (XRD), scanning electron microscopy (SEM), differential thermal analysis (DTA), thermogravimetric analysis (TGA), infrared spectroscopy (IR), 31P solid-state NMR, and adsorption isothermal analysis. Results showed that this compound has a layered structure with the formula K8Sb8P2O29·8H2O. It crystallizes in the monoclinic system with unit-cell parameters a = 23.95(2) A, b = 9.51(5) A, c = 8.19(3) A, and β = 124.77°. The structure can be intercalated by organic amine molecules and the potassium ions located in between layers can be exchanged by monovalent ions. Factors such as the initial Sb/P molar ratio, pH, reaction temperature, and cations which dominate the hydrothermal synthesis of the product were assessed.

Hydrothermal Synthesis and Characterization of a New Potassium Phosphatoantimonate, K8Sb8P2O29·8H2O

K3Sb3P2O14·5H2O was synthesized by a hydrothermal method, and characterized by X-ray diffraction (XRD), differential thermal analysis (DTA), thermogravimetry (TG) and 31P MAS NMR.

Hydrothermal synthesis and characterization of K3Sb3P2O14·5H2O

Hydrothermal Synthesis and Characterization of a New Potassium Phosphatoantimonate, K8Sb8P2O29×8 H2O.

A new potassium phosphatoantimonate with a composition of 4K 2 O · 4Sb 2 O 5 · P 2 O 5 · 8H 2 O, which crystallizes in a monoclinic system with a = 23.952 A, b = 9.515 A, c = 8.193 A, and β = 124.77, was hydrothermally synthesized and characterized by powder x-ray diffraction, chemical composition analysis, x-ray photoelectron spectroscopy, and 31 P MAS-NMR techniques. The potassium ion can be exchanged by other monovalent ions.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0884291400075804

Hydrothermal synthesis and characterization of a new potassium phosphatoantimonate

K3Sb3A2O14·5H2O (A P, As) were synthesized by use of a hydrothermal method, and the synthesis conditions are discussed in detail. Both phases were characterized by various techniques including scanning electron microscopy, XRD, XPS, 31P MAS NMR, IR, DTA–TG. The unit-cell parameters for K3Sb3P2O14·5H2O and K3Sb3As2O14·5H2O are slightly smaller than those for the corresponding phases synthesized by solid-state reactions.

Yonglin An

Papers

Hydrothermal Synthesis and Characterization of a New Potassium Phosphatoantimonate, K8Sb8P2O29·8H2O

Hydrothermal synthesis and characterization of K3Sb3P2O14·5H2O

Hydrothermal Synthesis and Characterization of a New Potassium Phosphatoantimonate, K8Sb8P2O29×8 H2O.

Hydrothermal synthesis and characterization of a new potassium phosphatoantimonate

Hydrothermal synthesis and characterization of K3Sb3A2O14·5H2O (A P,As)