Direct synthesis and the morphological control of highly ordered two-dimensional p6mm mesoporous niobium silicates with high niobium content

P. Srinivasu, C. Anand, S. Alam, K. Ariga, S. B. Halligudi, V. V. Balasubramanian, A. Vinu

Research output: Contribution to journalArticle

21 Scopus citations

Abstract

Here we demonstrate the preparation of highly ordered two-dimensional P6mm mesoporous niobium silicates with unprecedented loadings of niobium in the silica framework (up to nSi/nNb ratio of 6.1) and highly winding morphologies maintaining regularly aligned arrays of nanochannels through a simple adjustment of the molar water to hydrochloric acid ratio (nH2O/nHCl) in the synthesis gel using nonionic surfactant as a template in a highly acidic medium. X-ray diffraction (XRD), N2 adsorption, high-resolution scanning electron microscopy (HRSEM), energy-dispersive spectrometry (EDS), and high-resolution transmission electron microscopy (HRTEM) results provided strong evidence of the presence of highly ordered two-dimensional structure in the NbSBA-15 materials with a very high content of niobium and winding morphologies, whereas UV-visible diffuse reflectance spectroscopy (UV-vis DRS) confirmed the presence of tetrahedrally coordinated niobium in the silica framework. Moreover, the loading of Nb in the silica framework can be controlled by a simple adjustment of the n H2O/nHCl and the amount of Nb source in the synthesis gel. Thus, a hitherto unachieved loading of niobium in the silica framework with a controlled manner, considered by many researchers to be impossible to achieve for the highly ordered mesoporous SBA-15 materials because of the highly acidic synthesis condition and the framework connectivity constraints, has been reported. We also found that the Nb incorporation could be a way to control the morphlogy of the NbSBA-15 materials. The morphology of the materials changed from rod to semispherical to "winding road" shape with decreasing the nSi/nNb from 22.5 to 6.1. Moreover, the detailed mechanism on the morphological control as a function of Nb content has also been proposed. This simple one-step technique to control the morphology, which would be of general interest for the application requiring the materials with different morphology, and Nb loading in a highly acidic medium synthesis have not been reported so far.

Original languageEnglish (US)
Pages (from-to)10130-10140
Number of pages11
JournalJournal of Physical Chemistry C
Volume112
Issue number27
DOIs
StatePublished - Jul 10 2008

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