Layered niobium oxides pillaring and exfoliation

Abstract

Several ion-exchangeable layered niobates were applied to prepare modified layered photocatalysts. K 1- x La x Ca 2- x Nb 3O 10 ( x = 0, 0.25, 0.50, 0.75), a layered perovskite series, with variable interlayer cation density, were used for the modification of the interlayer space by pillaring of silica and titania. The silica-pillaring process was monitored by NMR and the thermal stability was also examined. Silica-pillar was successfully introduced to all the series of perovskites which showed good photocatalytic activity. The preparation of titania-pillared layered niobates was more difficult. In the case of KCa 2Nb 3O 10 ( x=0), we could not introduce a titania pillar, but in the case of K 0.5La 0.5Ca 5Nb 3O 10 ( x = 0.5) carrying less interlayer cation density, titania-pillar was introduced although the thermal stability was very poor. K 4Nb 6O 17, another type of layered niobate, was used for the exfoliation and restacking of the niobate sheets. The structure and photocatalytic activity of the product was examined.