Solvothermal and hydrothermal methods for preparative solid-state chemistry

Abstract

The use of solvothermal reaction conditions (hydrothermal when water is used) for the preparation of solid-state materials is surveyed to illustrate their use in preparative chemistry. A particular emphasis is placed on the formation of solid materials with properties suited for practical applications, the discovery of new compositions and crystal structures, and the control of crystallization that solution-mediated routes allow for such materials. Following some definitions and historical background, the various classes of materials that are accessed by solvothermal crystallization are reviewed, from microporous zeolites and their analogs, hybrid organic-inorganic solids (including coordination polymers and metal-organic frameworks) to condensed solids, spanning oxides and other chalcogenides, pnictides, halides and carbides. Analogies with mineral crystal chemistry are made, examples of layered materials provided, and recent work looking at composite materials is examined. A final section focusses on efforts made to understand the reaction pathways involved in the formation of materials under solvothermal conditions, from screening synthesis conditions, to models for crystallization, to experimental methods for following materials forming in situ under realistic reaction conditions.