PAPER www.rsc.org/dalton | Dalton Transactions Effective mesopore tuning using aromatic compounds in the aerosol-assisted system of aluminium organophosphonate spherical particles Tatsuo Kimura,* a Norihiro Suzuki, b Prashant Gupta b and Yusuke Yamauchi b,c Received 2nd February 2010, Accepted 25th March 2010 First published as an Advance Article on the web 26th April 2010 DOI: 10.1039/c002277b Spherical particles of ordered mesoporous aluminium organophosphonates (AOPs) were fabricated by spray-drying of precursor solutions containing Pluronic F127 (EO 106 PO 70 EO 106 ) at low temperature. Expansion of the mesopores (10.5 nm) were investigated using the triblock copolymer by the addition of typical aromatic compounds such as 1,3,5-trimethylbenzene (TMB) and 1,3,5-triisopropylbenzene (TIPBz). 1,3,5-TIPBz was more useful than 1,3,5-TMB for obtaining spherical AOP particles with large mesopores (>20 nm) because 1,3,5-TIPBz with the boiling point (235 ◦ C) much higher than the spray-drying temperature (~110 ◦ C) was accommodated in the surfactant assemblies effectively. The boiling point of 1,3,5-TMB (165 ◦ C) was not so high that it cannot stay completely in the surfactant assemblies during the spray-drying process, and thus smoothness of the surfaces was also deteriorated by evaporation of 1,3,5-TMB. Accordingly, the use of 1,3,5-TIPBz is effective for tuning uniform mesopores in the aerosol-assisted system of mesoporous AOP spherical particles with smooth surfaces. 1. Introduction Morphological controls of materials to films, fibers, monoliths, and so on are important for their practical applications based on optical, electronic, and photonic properties, which are also valid for the preparation of catalysts, adsorbents, membranes, and coatings. Surfactant templated silica has been explored as helpful supports for large proteins and enzymes in biocatalytic applications. 1 Spherical particles with well-ordered mesopores have also been eye-catching because of their potential uses in chromatography and drug delivery systems with controlled release properties. 2,3 It has been reported that aerosol-assisted approach combined with the sol–gel process is one of the most powerful methods to obtain spherical particles of silica-based mesoporous materials. 4–6 The aerosol-assisted methodology has been extended to the preparation of a wide variety of spherical particles of or- dered mesoporous silica possessing fluorescence, 4 luminescence, 7 photosensitive, 7 and catalytic properties (Al, Ti). 8,9 Besides, high loading of metal species (Al, Zr) was also useful for improv- ing the hydrothermal stability. 10 Structured materials containing metal salt, 11 oxides (Fe 3 O 4 , TiO 2 ), 12,13 metals (Au, Pd), 4,14 and polymer 4 has been reported until now. In triblock copolymer (EO n PO m EO n ) templated synthesis of mesoporous silica spherical particles, ordered mesopores are expanded in the presence of polyethylene glycol (PEG) 15 and hierarchical porosity is tailored by a Advanced Manufacturing Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Shimoshidami, Moriyama-ku, Nagoya, 463-8560, Japan. E-mail: t-kimura@aist.go.jp b World Premier International (WPI) Research Center for Materials Nanoarchitectonics (MANA), National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba, Ibaraki, 305-0044, Japan c Precursory Research for Embryonic Science and Technology (PRESTO), Japan Science and Technology Agency (JST), Kawaguchi-shi, Saitama, 332-0012, Japan using fluorocarbon surfactant 16 and polystyrene beads. 17 Mono- dispersity of mesoporous silica spherical particles was improved by utilizing vibrating orifice aerosol generator, 18 rather than by investigating the synthetic conditions. 19 Deposited film and ink-jet printed micropattern of ordered mesoporous silica are fabricated by the aerosol-assisted approach. 4,20–22 Aerosol-assisted synthesis of ordered mesoporous materials has mainly been developed in the case of silica, as described above. Although triblock copolymer templating has expanded the prospect to synthesize a large number of non-silica-based mesoporous oxide and phosphate films, 23,24 similar works on the preparation of non-silica-based materials by using spray- drying technique have started recently. 25–29 Spherical particles of mesoporous inorganic oxides (TiO 2 , ZrO 2 , CeO 2 , Al 2 O 3 , BaTiO 3 ) were synthesized, 25,26,28,29 but more or less limited to simple compositions. Further compositional variation will be demanded for fundamental development, because mesoporous silica with organic groups at the surfaces or inside the silicate frameworks and mesoporous carbon has already been reported on the basis of the aerosol-assisted approach 30–32 and spherical particles of mesoporous aluminium organophosphonate (AOP) was obtained as the first example of non-silica-based hybrid mesoporous spherical powders. 33 A synthetic strategy of ordered mesoporous AOPs from the reactions of diphosphonic acids with aluminium species in the presence of surfactants has showed the possibility to prepare a variety of non-silica-based hybrid mesoporous powders. 34–40 Lamellar AOP with a crystalline framework was also prepared under restricted conditions. 41 Facile fabrication of mesoporous AOPs to transparent films has been possible by spin-coating of clear precursor solutions, 42 and then we found recently that spherical powders were obtained by temperature-controlled spray- drying of similar precursor solutions. 33 Periodic mesostructures were constructed inside the spherical particles at low tempera- tures that solvents such as ethanol and water were evaporated. This journal is © The Royal Society of Chemistry 2010 Dalton Trans., 2010, 39, 5139–5144 | 5139