Simulating Self-Assembly of ZnS Nanoparticles into Mesoporous Materials Dean C. Sayle,* ,† Benoı ˆt C. Mangili, † Jacek Klinowski,* ,‡ and Thi. X. T. Sayle † Contribution from the DEOS, Cranfield UniVersity, Defence Academy of the United Kingdom, ShriVenham, Swindon SN6 8LA, UK, and Department of Chemistry, UniVersity of Cambridge, Lensfield Road, Cambridge CB2 1EW, UK Received July 17, 2006; E-mail: d.c.sayle@cranfield.ac.uk; jk18@cam.ac.uk Abstract: Characterization of materials is crucial for the quantification and prediction of their physical, chemical, and mechanical properties. However, as the complexity of a system increases, so do the challenges involved in elucidating its structure. While molecular simulation and modeling have proved invaluable as complements to experiment, such simulations now face serious challenges: new materials are being synthesized with ever increasing structural complexity, and it may soon prove impossible to generate models that are sufficiently realistic to describe them adequately. Perhaps, ultimately, it will only be possible to generate such models by simulating the synthetic process itself. Here, we attempt such a strategy to generate full atomistic models for mesoporous molecular sieves. As in experiment, this is done by allowing nanoparticles to self-assemble at high temperature to form an amorphous mesoporous framework. The temperature is then reduced, and the system is allowed to crystallize. Animations of atomic trajectories, available as Supporting Information, reveal the evolution of multiple seeds which propagate to form a complex framework. The products are polycrystalline mesoporous framework structures containing cavities connected by channels running along “zero”, one, two, and three perpendicular directions. We suggest that it is easier to generate these model structures by attempting to simulate the synthetic process rather than by using more conventional techniques. The strategy is illustrated using ZnS as a model system. Further development of the mathematics of minimal surfaces will advance our understanding of these structures. Introduction Frameworks of mesoporous molecular sieves accommodate internal channels and cavities. 1 They are important technologi- cally with applications in catalysis, 2 separation technology, ion exchange, sensors, etc. 3 An important class is the zeolites, which comprise periodic arrays of channels and cavities of molecular dimensions, enabling them to be used as shape-selective cata- lysts. However, in contrast to many catalysts in which the chem- istry occurs on the external surfaces, catalysis in zeolites occurs within a channel or cavity facilitating shape and size selectivity. 4 Zeolitic structures are complex, and therefore atomistic models have been constructed by extracting atom positions from XRD data. Computational visualization tools are used exten- sively to help us understand more easily the complex three- dimensional zeolitic framework structure. Moreover, in addition to structural characterization, atomistic simulation has enabled people to explore and predict the chemical properties of these microporous materials. 5 It has been suggested 2 that internal channels and cavities of mesoporous materials, such as zeolites, offer the promise of “nanosized chemical laboratories,” and considerable efforts have been focused on the design and synthesis of various framework structures. 6 The ultimate goal is to be able to use inorganic framework structures to mimic enzymatic processes. Many experimental approaches to the synthesis of framework structures have explored the use of templates. For example, Li et al. 1 synthesized mesoporous metal oxides with ordered mesopores using nanocrystals as the building block, held together by an amorphous “glue”. A different strategy was employed by Roggenbuck and Tiemann who used a carbon exotemplate to synthesize thermally stable MgO containing a periodic array of pores 4-8 nm in diameter. 7 Zou et al. 8 synthesized a chiral mesoporous germanium oxide with a primitive cell volume of 67 640 Å 3 and crystalline pore walls. This raised the possibility of fabricating an enantiopure material using chiral templates, a step closer to enzymatic mimicry. A review of templating methods for the preparation of porous † Cranfield University. ‡ University of Cambridge. (1) Li, D. L.; Zhou, H. S.; Honma, I. Nat. Mater. 2004, 3, 65-72. (2) Thomas, J. M.; Catlow, C. R. A.; Sankar, G. Chem. Commun. 2002, 2921- 2925. (3) Fe ´rey, G. Science 2001, 291, 994-995. (4) Foster, M. D.; Simperler, A.; Bell, R. G.; Delgado Friedrichs, O.; Almeida Paz, F. A.; Klinowski, J. Nat. Mater. 2004, 3, 234-238. (5) To, J.; Sokol, A. A.; French, S. A.; Catlow, C. R. A.; Sherwood, P.; van Dam, H. J. J. Angew. Chem., Int. Ed. 2006, 45, 1633-1638. (6) Huang, L. M.; Wang, Z. B.; Sun, J. Y.; Miao, L.; Li, Q. Z.; Yan, Y. S.; Zhao, D. Y. J. Am. Chem. Soc. 2000, 122, 3530-3531. (7) Roggenbuck, J.; Tiemann, M. J. Am. Chem. Soc. 2005, 127, 1096-1097. (8) Zou, X. D.; Conradsson, T.; Klingstedt, M.; Dadachov, M. S.; O’Keeffe, M. Nature 2005, 437, 716-719. Published on Web 11/08/2006 10.1021/ja0650697 CCC: $33.50 © 2006 American Chemical Society J. AM. CHEM. SOC. 2006, 128, 15283-15291 9 15283