Direct synthesis of large mesopore aluminosilicates templated by lyotropic liquid crystals Haoguo Zhu, Deborah J. Jones * , Nicolas Donzel, Jerzy Zajac, Marc Lindheimer Laboratoire des Agre ´gats Mole ´culaires et Mate ´riaux Inorganiques, UMR CNRS 5072, Universite ´ Montpellier II, Place Euge `ne Bataillon, 34095 Montpellier cedex 5, France Received 15 May 2006; received in revised form 31 August 2006; accepted 9 September 2006 Available online 13 November 2006 Abstract A family of aluminosilicates with large uniform mesopores and high specific surface areas is described in which the pore size may be adjusted in the range 3–7 nm by controlled hydrothermal treatment. This has the effect of swelling the liquid crystal arrangement and leads to increased pore volume, surface area and pore diameter. Aluminosilicates with Si/Al ratios between 10 and 80 are directly syn- thesised using tetraethoxysilane and aluminium nitrate by direct liquid crystal templating using the triblock copolymer, Pluronic P123. 27 Al MAS NMR spectra show that the majority of the aluminium is tetrahedrally coordinated, and that hydrothermal treatment favours incorporation of aluminium into the silica. The number of surface acid sites determined by adsorption of ammonia at 100 °C increases non-linearly with the Si/Al ratio. Ó 2006 Elsevier Inc. All rights reserved. Keywords: Aluminosilicate; Pore size control; Hydrothermal treatment; Ordered mesoporosity; Monolith 1. Introduction Ordered mesoporous materials have attracted much interest because of their potential applications as catalysts and adsorbents. The most studied class of mesoporous sol- ids are those that possess either a purely siliceous inorganic framework or a silica-based heteroatom-containing frame- work [1–5]. The latter are of great importance since the active sites in molecular sieves arise always from the hetero- atoms that introduce acidic and/or redox properties into the mesostructure [4]. Mesoporous aluminosilicates can be used as solid acid catalysts [5–8], and many endeavours have been made to improve their thermohydrolytic stability [3,7–11] so as to increase the range of applicability in catal- ysis. Effort was devoted a few years ago to the incorporation of heteroatoms into the framework of mesoporous siliceous SBA-15, which is prepared in strongly acid medium,using a triblock copolymer as directing agent [12]. Incorporation of aluminium into SBA-15 is difficult, because Al 3+ ions are soluble under the usual synthesis conditions. Since the hydrated Al 3+ cation cannot be introduced via a straight- forward condensation process with other framework form- ing species (silica), other methods have been sought, amongst which incorporation of aluminium by post-synthe- sis methods [13–16] has received considerable attention. One drawback of this approach is that the resulting grafted metal oxides tend also to occupy the channels or the exter- nal surface of the materials, where they can block reactant transfer and might play a negative role in catalysis [17]. Another disadvantage of post-synthesis modification is that the uniform mesostructures are sometimes destroyed [14]. In general, the efficiency of incorporation of aluminium into the porous framework depends on the procedure used, and other, more direct synthesis routes leading to ordered mes- oporous silicates incorporating heteroatoms are desirable. An alternative, and potentially more predictable, approach for the synthesis of heteroatom-substituted ordered mesoporous oxides is that of direct templating by 1387-1811/$ - see front matter Ó 2006 Elsevier Inc. All rights reserved. doi:10.1016/j.micromeso.2006.09.016 * Corresponding author. Tel.: +33 467 143330; fax: +33 467 143304. E-mail address: deborah.Jones@univ-montp2.fr (D.J. Jones). www.elsevier.com/locate/micromeso Microporous and Mesoporous Materials 99 (2007) 47–55