Exploring Zeolite Chemistry with the Tools of Surface Science: Challenges, Opportunities, and Limitations

Abstract

The complexity of catalysts that the surface science community has been able to address has increased substantially in a systematic manner, starting with metal and oxide single crystal surfaces and evolving to an atomistic description of clusters and nanoparticles on well-defined, planar supports. The next step in adding complexity is now to address surfaces of porous oxide materials, in particular of zeolites, which are the most extensively used catalysts in the industry. The recently reported successful fabrication of well-ordered thin films, consisting of planar arrangement of aluminosilicate polygonal prisms on a metal substrate counting with highly acidic bridging hydroxyl groups on the surface, represents the limiting case of infinitely large pore and cages in zeolites. This model system allows one to study reactions catalyzed by zeolites using the toolkit of surface science. In this Perspective, we describe the zeolitic model system, with its virtues and limitations, as well as the challenges, opportunities and expectations for the future in modelling porous catalysts by a surface science approach.

Oxidation of the Ru(0001) surface covered by weakly bound, ultrathin silicate films

“…Silicate and aluminosilicate thin films grown on metal substrates have recently received considerable attention as well-defined models for studying surface chemistry of silica-based materials, in particular of zeolites, as well as crystal-glass transitions exemplified by silica [1][2][3][4]. It is well established that the thinnest silica film forms a hexagonal layer of corner-sharing [SiO 4 ] tetrahedra (referred to as "silicatene" in analogy to graphene [5]) which is strongly bound to a metal support through Si-O-Metal linkages [6].…”

Ultra-thin silicate films on metals

“…For comparison, Al incorporation in silicate films only causes a red shift and broadening of the principal phonon bands (e.g. from 1300 to ~1270 cm -1 ) [78,85]. The STM images as well as LEED patterns of the Fe-containing films (insets in Fig.…”

“…All in all, the characteristics of the metal supported aluminosilicate films possessing Si-OH-Al surface species fit well into what is known about regular zeolitic surfaces. These films constitute the first well-defined model system where the surface properties of zeolites can be modeled by a surface-science approach [8,85].…”

Ionization‐Facilitated Formation of 2D (Alumino)Silicate–Noble Gas Clathrate Compounds

“…Their structures are shown in Figure B. These frameworks have been proposed as model systems for surface science studies of zeolites, [9b,10] which are the most widely used catalysts in the industry and the most important sorbent materials . The well‐ordered 2D (alumino)silicate frameworks with a thickness less than 5 Å were grown on a Ru(0001) surface, in which the distance between the (alumino)silicate framework and the ruthenium surface ranges between 2 and 4 Å depending on the coverage of interfacial chemisorbed oxygen .…”