Ethylene Epoxidation with Nitrous Oxide over Fe–BTC Metal–Organic Frameworks: A DFT Study

Abstract

The epoxidation of ethylene with N O over the metal-organic framework Fe-BTC (BTC=1,3,5-benzentricarboxylate) is investigated by means of density functional calculations. Two reaction paths for the production of ethylene oxide or acetaldehyde are systematically considered in order to assess the efficiency of Fe-BTC for the selective formation of ethylene oxide. The reaction starts with the decomposition of N O to form an active surface oxygen atom on the Fe site of Fe-BTC, which subsequently reacts with an ethylene molecule to form an ethyleneoxy intermediate. This intermediate can then be selectively transformed either by 1,2-hydride shift into the undesired product acetaldehyde or into the desired product ethylene oxide by way of ring closure of the intermediate. The production of ethylene oxide requires an activation energy of 5.1 kcal mol , which is only about one-third of the activation energy of acetaldehyde formation (14.3 kcal mol ). The predicted reaction rate constants for the formation of ethylene oxide in the relevant temperature range are approximately 2-4 orders of magnitude higher than those for acetaldehyde. Altogether, the results suggest that Fe-BTC is a good candidate catalyst for the epoxidation of ethylene by molecular N O.

Metal–organic and covalent organic frameworks as single-site catalysts

“…The iron exchanged analogue of HKUST-1, FeBTC, was studied by Maihom et al for the catalytic ethylene epoxidation with nitrous oxide. 289 By performing DFT calculations with the M06-L local functional as implemented in Gaussian09, they unveiled the reaction mechanism and underlying energy profile of the N 2 O decomposition and the subsequent ethylene epoxidation ( Fig. 19 ).…”

Density Functional Investigation of the Conversion of Furfural to Furfuryl Alcohol by Reaction with i-Propanol over UiO-66 Metal–Organic Framework

“…This method is suggested for the system of transition metals and inorganic and organometallic metals . Its usability has been tested previously for studying the adsorption and reaction mechanisms occurring over various types of MOF materials. − We employed the double-ζ of the Stuttgart–Dresden pseudopotential to describe Zr, Hf, and Ti and the 6-31G (d,p) basis set for all the other elements. During geometry optimizations, the entire UiO-66 structure, except for terminating hydrogen, was allowed to relax.…”

A mechanistic study of ethanol transformation into ethene and acetaldehyde on an oxygenated Au-exchanged ZSM-5 zeolite

“…It has been successfully used for investigating the adsorption and reaction mechanisms over zeolites 23,[29][30][31][32][33][39][40][41][42][43][44][45] and also over other materials such as metalsorganic frameworks. [46][47][48][49][50][51] The 6-31G(d,p) basis set was used to treat Al, Si, C, O and H atoms, while the Au atom was described by the Stuttgart Effective Core Potential basis (ECP). 52 During the geometry optimizations, only the 5T cluster of the active site region [(^SiO) 3 (AuO)Al(OH)Si^] and the adsorbate molecule were allowed to relax, while the remaining atoms were xed at the crystallographic coordinates.…”