Facile Assembly of Dispersed ZrMCM‐41 Nanoparticles Promoted in‐situ by Zirconium Salt

Abstract

Mesoporous ZrMCM-41 nanoparticles were synthesized by a usual way where tetraethyl-orthosilicate (TEOS) and zirconium nitrate were used as the inorganic precursors. The obtained nanoscale ZrMCM-41 was characterized by X-ray diffraction, N 2 physis-sorption, scanning electron microscopy and transmission electron microscopy. Characterization results revealed that zirconium salt added in the synthesis had a crucial effect on the assembly of nanoscale ZrMCM-41 with relatively uniform particle size, which was rarely observed in reported studies for ZrMCM-41 synthesized using the similar method. Meanwhile, the possible mechanism behind the synthesis was discussed based on the character of hydrolysis and condensation of TEOS and the mild acidic environment induced by the hydrolysable zirconium salt under aqueous conditions. Thus obtained nanoscale ZrMCM-41 with developed pore structures may be advantageous to general applications in catalysis or adsorption host-guest chemistry in terms of efficient mass transport of guest molecules.Keywords: Hydrolysis; Condensation; Sol-gel preparation. INTRODUCTIONOrdered MCM-41, reported by the Mobil corporation, is one of the most popular mesoporous materials and has been widely investigated. 1,2 The MCM-41 material possesses a uniform hexagonal array of linear pores constructed with a silica matrix like a honeycomb, and is very promising due to its high pore volume (~0.6 cm 3 /g), surface area (~800 m 2 /g) and tunable pore opening (2~10 nm) with narrow size distribution. Even though it is a fascinating candidate for the catalysis of organic transformations, pure silica-based MCM-41 shows limited application value due to the lack of active sites in the silica walls. Fortunately, catalytic activity like acid or redox performance can be generated by modification of the siliceous framework with heteroelements. 3 However, despite the noticeable success of microporous zirconium silicates in selective oxidation reactions, 4 the synthesis of ZrMCM-41 with developed mesopores is still extremely important in the field of redox catalysis, especially for those reactions involving bulky organic substances. 5 Apart from being directly used as catalysts, ordered ZrMCM-41 materials with highly specific surface area are also good supports widely applied for various active components like nickel oxide, 6 Pt/H 3 PW 12 O 40 7 and Ir/Pt 8 and so on, due to the favorable promoting effect of ZrMCM-41 in the designed reactions. 9 However, most previous reports on ZrMCM-41 were mainly focused on the synthesis and catalytic application of activators supported. 6-10 One key issue associated with the applicability of ZrMCM-41, namely the morphological properties like nanoscale particle, was rarely reported in previous studies. 11 In the study, ordered ZrMCM-41 was synthesized by traditional method using TEOS and zirconium salt as raw materials. However, it was found that nanoscale ZrMCM-41 with relatively uniform particle size distribution could be conveniently promoted in-situ by zirconium salt, even thoug...