Mixed salts of cesium and ammonium derivatives of 12-tungstophosphoric acid: Synthesis and structural characterization

Mixed salts of cesium and ammonium derivatives of H3PW12O40 ((NH4)xCsyH0.5PW) were synthesized by a precipitation/ion exchange method with a different addition order for each cation. The produced salts were characterized by FTIR, XRD, 31P MAS NMR, SEM, pore size and the BET method. FTIR demonstrated that the materials maintained the Keggin structure under all tested conditions. BET results showed that salts formed by proton substitution from ammonium to cesium had much higher surface areas. Characterization by 31P MAS NMR and XRD, demonstrated that the salt structures varied sharply with the degree of hydration. After calcination, the materials were confirmed to have characteristics of solid solutions with random distribution of the cations with similar crystallographic patterns. The primary nanocrystals aggregated to form solids with mesoporous and microporous structures, created by partial unidirectional growth of the nanocrystals during formation of the bigger, round microcrystallites about 0.3–1 μm in size.

Graphical abstract.Figure optionsDownload full-size imageDownload high-quality image (189 K)Download as PowerPoint slideResearch highlights▶ New salts of cesium and ammonium derivatives of H3PW12O40 were synthesized by precipitation. ▶ The properties of the mixed salts depend on the order of precipitation. ▶ The salts precipitated by ammonium followed by cesium have areas four times than the opposite. ▶ The nanocrystals aggregated forming mesoporous–microporous structures. ▶ The structures are formed by partial unidirectional growth.