Ionothermal synthesis, the use of ionic liquids as both solvent and template (structure-directing agent), has been used to prepare zeolites and inorganic-organic hybrids such as metal-organic frameworks. The underlying properties of the ionothermal method are discussed, and it is compared with traditional hydrothermal preparative methods. The materials resulting from ionothermal synthesis are described, and any structural features that can be related to the ionic liquid used as the solvent are discussed. Future areas of potential interest are also considered.

Ionothermal synthesis, the use of an ionic liquid as both solvent and structure-directing agent, has been used to synthesize three different cobalt aluminophosphate zeolites. Two of the materials are isostructural with solids prepared previously and have the AEI and SOD framework types. SIZ-7 is a novel zeolite structures that is closely related to the family of 8-ring zeolites consisting of the MER, GIS, and PHI frameworks. Single-crystal X-ray diffraction of SIZ-7 indicates that the distribution of cobalt among the four possible tetrahedral sites is unequal.

The use of organic templates (also called structure-directing agents) remains one of the most successful methods of preparing new inorganic materials. [1,2] Many of the most important recent advances in porous solids in particular depend on the clever use of organic species as templates to produce new zeolites, [3][4][5] transition-metal phosphates [6] or oxides, [7] and to make synthetic methods more efficient.[8]Ionothermal synthesis, where an ionic liquid is both the solvent and source of the template, provides opportunities to develop new synthetic routes that are based on different chemistry to traditional hydrothermal approaches. [9][10][11][12] Herein we describe the controlled use of deep-eutectic solvents (DESs) that are unstable at high temperatures as the media for ionothermal reactions. The organic template is not added to the reaction mixture in the normal way, but is delivered to the reaction by the breakdown of one of the components of the DES itself, demonstrating how the unique solvent properties of these ionic liquids can be harnessed to produce new types of solid.A DES is a mixture of two compounds where there is a depression in the freezing point of the mixture compared with that of the separate components. One class of DES comprises mixtures of organic halide salts with hydrogen-bond donors, such as amides, amines, alcohols, and carboxylic acids. [13,14] The freezing-point depression in the mixture results from the formation of halide ion-hydrogen-bond-donor supramolecular complexes that alter the free energy of the solid phase compared to the liquid. DESs are therefore predominantly ionic liquids, with properties that differ markedly from those of molecular liquids and salts dissolved in molecular solvents. Such DESs have features that make them excellent choices

A new layered open framework aluminophosphate has been prepared by ionothermal synthesis using an ionic liquid as the reaction solvent and structure-directing agent.

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