An opportunity for utilizing earth-abundant metals through the mesostructural design of metal phosphate-based materials

This review focused on the surfactant-assisted synthesis of metal phosphate-based materials and summarized their potentials based on the design of mesoporous structure as well as composition and crystal structure of the inorganic frameworks. In cases of Ti and Zr, metal phosphate frameworks are constructed through two synthetic pathways. One is a step-by-step process including phosphation of as-synthesized metal oxides. The phosphation process is helpful for stabilizing the mesoporous structures constructed by thin inorganic frameworks. A direct synthesis is possible when thickness of frameworks is enough for stabilizing mesoporous structures prepared using polymeric surfactants like EOnPOmEOn type triblock copolymer. Other mesoporous metal (e.g., Nb, Ta, Cr, Ga, Sn) phosphates are directly obtained using CnTMA type surfactants. In addition, unique mesostructural alterations are observed for some metal (e.g., Mn, Fe, Co, Ni, Ca as redox/ionic) phosphates. According to the nature of metal oxide like units and surface property of metal phosphate frameworks, resultant mesoporous materials are broadly investigated as newly designed catalysts and/or catalyst supports, for selective oxidation, acidity-dependent, photo-induced, and electrochemical reactions. For an enrichment of electrochemical activities, crystallized frameworks with demanded P/M ratio are required for fabricating electrodes for dye-sensitized solar cell, fuel cell and lithium-ion battery. Consequently, the contents of this review provide an opportunity for designing mesostructure of a wide variety of metal phosphates containing earth-abundant metals.