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

The epoxidation of ethylene with N2O over the metal-organic framework Fe-BTC (BTC = 1,3,5-benzentricarboxylate) has been investigated by means of density functional calculations. Two reaction paths for the production of ethylene oxide and of acetaldehyde were 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 N2O to form an active surface oxygen on the Fe site of Fe-BTC which subsequently reacts with an ethylene molecule, forming an ethyleneoxy intermediates. This intermediate can then either be selectively transformed via 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 ethylene oxide production requires an activation energy of 5.1 kcal/mol, which is only about one third than the activation energy for the acetaldehyde formation (14.3 kcal/mol). The predicted reaction rate constants for the formation of ethylene oxide in the relevant temperature range are about 2-4 orders of magnitude higher than the ones for the acetaldehyde. Altogether, the results suggest that Fe-BTC is a good candidate catalyst for the epoxidation of ethylene by molecular N2O.