Zeolites with isolated-framework and oligomeric-extraframework hafnium species characterized with pair distribution function analysis. Issue 12 (12th March 2018)

• Record Type: Journal Article
• Authors: Iida, Takayuki; Ohara, Koji; Román-Leshkov, Yuriy; Wakihara, Toru
• Is Part Of: Physical chemistry chemical physics. Volume 20:Issue 12(2018)
• Page Start: 7914
• Page End: 7919
• Publication Date: 2018-03-12
• Subjects: Chemistry, Physical and theoretical -- Periodicals; 541.3
• DOI: 10.1039/c8cp00464a
• Languages: English
• ISSNs: 1463-9076

Abstract

Abstract : PDF analysis enabled the visualization and identification of framework and extraframework HfO x species in the post-synthetically produced *BEA zeolites. Abstract : Zeolites containing framework heteroatoms ( e.g., Ti, Sn, and Hf) with open coordination sites behave as solid-state Lewis acids and exhibit remarkable catalytic properties unachievable with bulk oxides. However, direct evidence confirming the incorporation of such heteroatom species into the zeolite framework is difficult to obtain because of the limited number of analytical methods capable of discerning framework incorporation from extraframework species. In this work, the structural environments of hafnium (Hf) framework and extraframework species added post-synthetically into *BEA zeolites were analyzed using coupled pair distribution function (PDF) and diffuse reflectance (DR) UV-vis measurements. PDF analysis enabled the visualization and identification of framework and extraframework HfO x species, both of which were undetectable by traditional X-ray and neutron diffraction methods. Reactivity data from the aldol condensation of benzaldehyde and acetone confirmed that framework Hf species are responsible for catalytic activity.