Shape Selectivity tunnel

A peculiar shape-selective behavior has been observed in a Cu-based MOF containing one-dimensional tunnels with narrow necks at regular distances of... 

We have shown that [Ni2+]-OMS-2 and [N 2+]-OMS-1 catalyze the selective conversion of hexane to 1-hexene. Stainless steel flow reactors of 1/4 diameter containing 0.5 g catalyst, charges of 7 g n-hexane in 2 h, 1 atm pressure and temperatures of 500°C are used in these experiments. Both gas chromatography (GC) and mass spectrometry (MS) analyses are done to monitor product distributions. Conversions as high as 60% and selectivities of 90% (to the terminal olefin) have been observed for the OMS-2 system. This may be a consequence of the better shape selectivity of [Ni2+]-OMS-2 (4.6 A tunnel) versus (Ni2+]-OMS-1 (6.9 A). The latter material is not as selective or active. Systems that do not contain N 2+ are totally inactive.91 There is precedence for dehydrogenation activity of these systems since manganese nodules have been reported to be excellent catalysts for dehydrogenation of cyclohexane.63... 

A square. These materials with tunnels bigger than or equal to (2 X 2) have counter cations because the oxidation state of some manganese is lower than +4.0. The materials have cation-exchange properties [2-4]. Like zeolites, the materials might be used as shape selective catalysts and molecular sieves because of their tunnel structures and ion-exchange properties [5]. 

Section II will discuss the basic phenomena of inelastic tunneling from the viewpoint of the experimentalist. Section III will treat peak shapes, shifts, and widths. Section IV will deal with intensities and selection rules in IETS. Finally, Section V includes some recent applications of IETS to the fields of chemisorption and catalysis, and to the at first glance unrelated field of surface enhanced Raman spectroscopy. 

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