The polyelectrolyte-MoO3 hybrids: Bottom up building of a layered anionic exchanger

• A novel method, a hydrothermal treatment, intercalates PDDACl and PAHCl in MoO3.
• Intercalation expands the interlayer space of MoO3to ca the double of the initial one.
• Intercalation causes the reduction of Mo6+ to Mo5+ as shown by UV–vis spectroscopy.
• A new anion exchanger was created.

One-pot intercalation of poly(diallymethylammonium chloride) (PDDACl) and poly(allylamine hydrochloride) (PAHCl) between the layers of crystalline MoO3 was achieved for the first time using hydrothermal treatment. An experimental study monitoring the time of reaction and temperature of hydrothermal treatment showed that at 96 h and 150 °C the organic–inorganic [PAHCl]0.18[PAH]0.38MoO3 and [PDDACl]0.26[PDDA]0.24MoO3 hybrid materials were produced. In these conditions the MoO3 host was able to expand its interlayer spacing from 0.64 to ca. 1.1 nm upon the intercalation of PDDACl and to approximately 2.2 nm with the use of PAHCl. The materials prepared with PAHCl exhibit a larger interlayer space and have a larger amount of intercalated polymer than those with PDDACl because of the PAHCl smaller charge density. The characterization of these hybrid materials using powder XRD, Raman, FTIR, fluorescence and UV–vis DRS spectroscopy, SEM and TG/DTG analysis supported the intercalation of the polymer between MoO3 layers. UV–Vis DRS analysis clearly shows the presence of the mixed-valence Mo5+/Mo6+ couple in the MoO3 framework after the polyelectrolyte intercalation which indicates charge transfer from the polymer to the MoO3 host. FTIR study also revealed short distances structural disorder related to presence of Mo5+ centers after the intercalation. The hybrid materials produced, [PDDACl]0.26[PDDA]0.24MoO3 and [PAHCl]0.18[PAH]0.38MoO3 showed that approximately 53.0% and 32.0% of chloride ions are available for anionic exchange, respectively. These solids were employed as anion exchangers using cyanine dye; the emission band of the dye was monitored after the exchange as an indication of intercalation success. The cyanine dye containing hybrids presented an emission band centered at 602 nm even after extensive extraction with methanol.

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