Selective Liquid-Phase Sorption of Small Aliphatic Normal Alcohols on a Flexible Assembly Composed of Keggin Polyoxometalate

Single crystals of Na3[Fe3O(O2CCH2OCH3)6(H2O)3][α-SiW12O40]·13.5H2O (1a) and their nanoparticles (2a) have been synthesized by self-assembly of the constituent ions and a one-pot sonochemical reaction, respectively. Their corresponding activated phases, 1b and 2b, were obtained by desorption of crystallization water through a thermal process. The sorption capacity of 2b for methanol vapor, owing to the lack of well-defined pores, was significantly less than 1b, which was confirmed by thermogravimetric analysis. Liquid-phase sorption of small aliphatic alcohols (C1–C4) was applied to characterize the sorption behavior of 1b. The lattice flexibility was revealed by unit-cell volume calculation for 1b after sorption of each alcohol by using powder X-ray diffraction data. Also, investigation of the sorption isotherms, fitting experimental kinetic data to the Lagergren and Ho models, and calculation of the activation energies for sorption of each alcohol were carried out. Finally, the sorption selectivity of 1b towards the alcohols was determined.