Interface Between Alkylammonium Ions and Layered Aluminophosphates Materials: A Combined Theoretical and Experimental Study Maddalena D’Amore, † Chiara Bisio, † Giovanni Talarico, ‡ Maurizio Cossi,* ,† and Leonardo Marchese* ,† Dipartimento di Scienze e Tecnologie AVanzate, Centro Interdisciplinare Nano-SiSTeMI, UniVersita` del Piemonte Orientale “A. AVogadro”, Via Bellini 25/G, Alessandria, Italy, and Dipartimento di Chimica, “Paolo Corradini” UniVersita` di Napoli “Federico II”, Complesso Monte S. Angelo, Via Cintia, 80126 Napoli, Italy ReceiVed April 4, 2008. ReVised Manuscript ReceiVed May 29, 2008 n-Butylammonium ions intercalated in a layered aluminophosphate (AlPO-ntu) with kanemite-type structure (hereafter AlPO-kan) have been studied by IR spectroscopy and modeled with density functional theory (DFT) calculations. This joint approach clarified the local structure of the inorganic/organic interface, not yet described. The acidity of the surface hyroxyls was investigated with a finite cluster model, while the structure and the theoretical IR spectra were obtained with 3D and 2D periodic boundary conditions. In the structure here optimized, each organic ion forms three hydrogen bonds with the surface phosphate and aluminate oxygens; the theoretical frequencies, including anharmonic corrections on the main stretching modes, were compared to the experimental IR spectra. The very satisfactory agreement confirms the optimized structure and allowed all the observed peaks to be assigned, providing for the first time a clear-cut interpretation of the broad and complex absorption at 2800-1700 cm -1 in terms of Fermi-type resonances. 1. Introduction Layered aluminophosphates are intermediates in the synthesis of microporous molecular sieves with channels and cavities of molecular dimensions similar to well-known zeolites. 1 CoSAPO-44 and CoAPO-44, 2 for instance, are formed via layered materials, and several other alumino- phosphate molecular sieves, such as AlPO 4 -5, AlPO 4 -22, and AlPO 4 -16 and the silicoaluminophosphate SAPO-35, are formed from a common lamellar material, the AlPO 4 -L, during the hydrothermal treatment of a gel containing Al 2 O 3 , P 2 O 5 , SiO 2 , and hexamethyleneimine, in aqueous media or in ethylene glycol. 3 In addition, in the synthesis of chabazite aluminophosphates directed by morpholine, the formation of a layered prephase was also invoked. 4 The synthesis of aluminophosphate and silicoalumino- phosphate molecular sieves from layered aluminophosphates with structure similar to the hydrated silicates used in zeolite synthesis 5–9 is relevant for the possibility to obtain novel molecular sieves with unusual morphology and surface properties. However, until the CAL-n family of microporous silicoaluminophosphate molecular sieves was presented, 1 there were no good candidates as layered reactants, that is, lamellar aluminophosphates and silicoaluminophosphates with structures similar to the hydrated layered silicates. It is from the pionering work of Cheng et al., 10 who reported the synthesis of the layered aluminophosphate AlPO-ntu (whose empirical formula is AlPO 2 (OH) 2 [NH 2 (CH 2 ) x CH 3 ], x ) 3, 5, 7), employing amines as structure directing agents, that the perspective to obtain AlPOs and SAPOs molecular sieves using layered materials as precursors became possible. It was proposed that the structure of AlPO-ntu is analogous to that of the siliceous kanemite, and for this reason hereafter the AlPO-ntu is called organomodified AlPO-kanemite (AlPO-kan). 10 This layered material has been transformed into silico-aluminophosphates with chabazite-like structure, the CAL-1, 11 using hexamethyleneimine as structure direct- ing agent. Moreover, CAL-4 with structure similar to SAPO- 44, CAL-5 (AlPO-34 like structure), and CAL-3 with a levine structure have been also synthesized using AlPO-kan as precursor. 12 * To whom correspondence should be addressed. E-mail: maurizio.cossi@ mfn.unipmn.it. Tel.: 39 0131360267. Fax: 39 0131670250. † Universita` del Piemonte Orientale “A. Avogadro”. ‡ “Paolo Corradini” Universita` di Napoli “Federico II”. (1) Pastore, H. O.; Coluccia, S.; Marchese, L. Annu. ReV. Mater. Res. 2005, 35, 351. (2) Lee, Y. J.; Chon, H. Microporous Mater. 1997, 11, 253. (3) Venkatathri, N.; Hedge, S. G.; Ramaswamy, V.; Sivasanker, S. Microporous Mesoporous Mater. 1998, 23, 277. (4) (a) Vistad, Ø. B.; Akporiaye, D. E.; Lillerud, K. P. J. Phys. Chem. B 2001, 105, 12437. (b) Vistad, Ø. B.; Akporiaye, D. E.; Taulelle, F.; Lillerud, K. P. Chem. Mater. 2003, 15, 1639. (5) Zones, S. I. U.S. Patent 4,676,958, 1987. (6) Zones, S. I. U.S. Patent 4,689,207, 1987. (7) Pa´l-Borbe´ly, G.; Beyer, H. K. Stud. Surf. Sci. Catal. 1999, 125, 383. (8) Salou, M.; Kiyozumi, Y.; Mizukami, F.; Nair, P.; Maeda, K.; Niwa, S. J. Mater. Chem. 1998, 8, 2125. (9) Selvam, T.; Baudarapu, B.; Mabaude, G. T. P.; Toufar, H.; Schweiger, W. Microporous Mesoporous Mater. 2003, 64, 41. (10) Cheng, S.; Tzeng, J.; Hsu, B. Chem. Mater. 1997, 9, 1788. (11) Gieck, C.; Bisio, C.; Marchese, L.; Filinchuk, Y.; da Silva, C. E.; Pastore, H. O. Angew. Chem., Int. Ed. 2007, 46, 8895. (12) Pastore, H. O.; Martins, G. A. V.; Strauss, M.; Pedroni, L. G.; Superti, G. B.; de Oliveira, E. C.; Gatti, G.; Marchese, L. Microporous Mesoporous Mater. 2008, 107, 81. 4980 Chem. Mater. 2008, 20, 4980–4985 10.1021/cm8009594 CCC: $40.75  2008 American Chemical Society Published on Web 07/12/2008