Hydrothermal synthesis as a versatile tool for the preparation of metal hexacyanoferrates: a review

Metal hexacyanoferrates (HCF), which are produced by hydrothermal synthesis, have received increasing attention for different applications due to their unique physicochemical properties, such as three-dimensional framework with large open sites and metal sites with different oxidation states. The hydrothermal method is a simple and established synthesis technique, with the ability to synthesize unstable materials near the melting point, the possibility to synthesize large and good quality crystals and to obtain tunable size particles, controlled agglomeration, and low contamination by impurities, and in which the properties of products depend on the formation mechanism and hydrothermal conditions. Focusing on the structure of HCF including crystallography and morphology from the literature, this review discusses the effects of synthesis conditions (metal precursor, hydrothermal temperature, and duration) and post-treatment (acid addition and calcination) on the formation of metal hexacyanoferrates. Furthermore, structural modifications and current progress toward the application of HCF as catalysts, sensors, adsorbents, electrochromic displays, and energy storage are also summarized in this review.