Self-Assembled Mesoporous Zirconia and Sulfated Zirconia Nanoparticles Synthesized by Triblock Copolymer as Template Swapan K. Das, † Manas K. Bhunia, † Anil K. Sinha, ‡ and Asim Bhaumik* ,† Department of Materials Science, Indian Association for the CultiVation of Science, JadaVpur, Kolkata, 700 032, India, and Catalytic ConVersion and Process DeVelopment DiVision, Indian Institute of Petroleum, Dehradun, 248 005, India ReceiVed: February 16, 2009 Self-assembled highly crystalline ZrO 2 nanoparticles with mesoscopic ordering have been synthesized by a simple chemical process, evaporation-induced self-assembly (EISA), in the presence of an amphiphilic block copolymer, pluoronic F127, as template. The mesoscopic assembly of the ZrO 2 nanoparticles and the crystallinity of the pore walls were studied by using small- and wide-angle X-ray powder diffractions and transmission electron microscopy (TEM) image analysis. N 2 sorption studies and high-resolution TEM results further revealed that mesopores are formed by the regular arrangement of the ca. 7.0 nm size nanoparticles and their broad interparticle pore size distribution. This mesoporous ZrO 2 nanomaterial has been sulfated by 1 N sulfuric acid, and the resulting sulfated material showed strong acidity in NH 3 -temperature-programmed desorption (TPD) analysis. Catalytic activity of the mesoporous sulfated zirconia material has been utilized in the Friedel-Crafts alkylation (benzylation) of mesitylene, where it showed excellent catalytic efficiency for the monoalkylated products. Introduction Mesoporous materials have attracted widespread interest in different areas of science because of their unique properties like high surface area, uniform pore size distribution, and large pore volume since the first report of M41S materials. 1 Their convenient syntheses through different chemical routes, their large diversity of framework structures, and their novel proper- ties have become a very active area of research for over a decade, and these materials can find important applications in many frontier areas such as catalysis, 2 adsorption, 3 biomolecular separation, 4 drug delivery, 5 and so on. The unique feature for the synthesis of mesoporous materials is focused on the use of supramolecular assembly of template molecules as structure- directing agent. 1 The soft templates such as triblock copolymers or surfactants, which form the self-aggregated superstructures in solution phase, play the key role in directing the formation of organized porous structures. 6 This approach for the synthesis of mesoporous silica-based materials has been extended to nonsilicious oxides, which contain semicrystalline domains within their thick pore walls. Nonsiliceous mesoporous materials are often more difficult to synthesize by precipitation routes and often exhibit poor crystallinity and low thermal stability. In the search for catalytically interesting new mesoporous materials, 2 a large number of synthetic strategies have been reported for the different mesoporous metal oxides. Although a generalized synthesis approach for the semicrystalline meso- porous materials was reported by Yang et al., 7 synthesis of fully crystalline networks is still a major area of interest. On the other hand, the self-organization of nanoparticles is another thrust area of research for the practical application of the nanomaterials in the fabrication of a nanodevice. 8 For nanometer-sized particles, the ratio of the number of atoms in the surface to the number in the bulk is much larger than for micrometer-sized materials, and this can lead to novel properties. The unique nanostructures of materials make them potentially useful in a wide range of advanced applications, such as sensing, 9 catalysis, 10 magnetism, 11 optoelectronics, 12 and so forth. Self-assembly through noncovalent interactions like H-bonding interaction, 13 electrostatic interaction, 14 charge-transfer interac- tion, 15 acid/base proton transfer, 16 van der Waals forces, 17 host-guest interaction, 18 and so forth is an effective technique that has been proven successful in forming different nanostruc- tured materials. Thus, understanding different self-assembly processes that direct the precise optimization of the functional properties of the nanomaterials having potential applications is very crucial. 19 Nanoparticles (NPs) 1-10 nm in size have some unique properties because of their inherent large surface-to-volume ratio and quantum size effects, which differ from those of the corresponding bulk materials. 20 Self-assembly of these NPs into a mesoporous material with multiscale structures is of remark- able significance because of their unique properties associated with the nanostructures. There are some reports on self-assembly of different nanoparticles forming the mesoporous structures; 21-26 Chen et al. 26 reported nanocrystalline zirconia hydrothermally using mixed surfactant route at 403 K. They obtained disordered nanocrystalline zirconia in mixed tetragonal and monoclinic phases exhibiting both macropore and small mesopore. How- ever, designing the self-assembly of zirconium oxide nanopar- ticles with controllable pore structure using surfactant templating pathway is still challenging. Thus, it is highly desirable to design a mesoporous material with pore walls composed of crystalline nanoparticles and to tune their surface chemical and physical properties. Moreover, most of the previously reported meso- porous zirconia materials synthesized through surfactant tem- plating pathway 27 possess amorphous framework, and in many cases, these materials undergo structural collapse of their nanostructure on high-temperature crystallization/calcination, * To whom correspondence should be addressed. E-mail: msab@iacs.res.in. † Indian Association for the Cultivation of Science. ‡ Indian Institute of Petroleum. J. Phys. Chem. C 2009, 113, 8918–8923 8918 10.1021/jp9014096 CCC: $40.75  2009 American Chemical Society Published on Web 04/22/2009