Local Structures of Heteroatom Environments and their Effects on the Reactivities of Alumino- and Borosilicates – ALUBOROSIL

Till now, ?heteroatom' sites, such as Al or B, have been exceedingly difficult to characterize, due to their complicated combinations of order and disorder within silicate/silica frameworks. Such local compositional and structural features are important, because they crucially influence the macroscopic adsorption and catalytic reaction properties of these materials. Despite the technological importance of these catalytic solids, e.g., aluminosilicate zeolites are responsible for nearly all of the world's current gasoline production; much remains unknown at a molecular level about the origins of their activities. This is principally because of insufficient knowledge about the local environments at the heteroatom sites that are responsible for the desirable catalytic properties of catalysts, such as alumino- and borosilicates. The main objectives of the proposed project are therefore: (i) to develop and apply new state-of-the-art methods of solid-state nuclear magnetic resonance (NMR) spectroscopy to establish the local compositions and structures at and near catalytically important heteroatom moieties in nanoporous silicate and silica materials; (ii) to use the new resulting insights to design and control heteroatom environments in porous silicate and silica frameworks in order to modify and thereby improve their macroscopic adsorption and reaction properties; and (iii) to educate and train students to provide strong fundamental understanding of state-of-the-art methods of NMR spectroscopy and syntheses, characterization, and properties of new catalytic materials. The intellectual merit of the proposed research is that it will yield transformative insights on one of the most important issues in catalysis, namely establishing the molecular origins of the high activities and high selectivities of heteroatom-containing porous silicates and silicas. This will be achieved by combining and exploiting recent progress made separately in the Depts. of Chemical Engineering and Chemistry at the University of California, Santa Barbara (UCSB) and at the Centre National de la Recherche Scientifique (CNRS) Laboratoire de Conditions Extrêmes et Matériaux: Haute Température et Irradiation (CEMHTI) in Orléans, France. The UCSB groups have developed versatile procedures for syntheses and characterization of molecularly ordered zeolites, layered silicates, and functionalized surfaces, which will be elucidated by a combination of experimental and theoretical methods, especially multidimensional NMR spectroscopy. Direct measurements of heteroatom species introduced into such materials will be enabled by the Orléans team's leadership in the development and applications of correlation NMR techniques, including quadrupolar nuclei, (27Al, 11B, 17O) and notably as applied to ordered and disordered alumino- and borosilicates. The molecular-level understanding gained from these investigations will be correlated with macroscopic physicochemical (e.g., acidity, reactivity, adsorption) properties of the materials to obtain new insights on the molecular origins of their complicated catalytic behaviors. The broader impacts of the proposed project include the demonstration of new and general approaches for the measurement, understanding, design, and improvement of the local compositional and structural features that account for the reactivities of diverse classes of catalysts. Training of students in these areas is important, both nationally and internationally, and participation by students from underrepresented groups will be actively promoted. The collaborative efforts between UCSB and CEMHTI in Orléans will provide cross-cultural educational and research opportunities for students between two complementary and well-equipped groups. The interdisciplinary training that students will receive in the synthesis and characterization of new catalysts will be broadly transferrable. It is expected that the insights gained from the proposed project will enable students and the broader scientific community to develop next-generation materials aimed at improving the energy-efficiency of processes and devices.