ZIF-8 as a Catalyst in Ethylene Oxide and Propylene Oxide Reaction with CO2 to Cyclic Organic Carbonates

Abstract

CO2 is an important by-product in epoxides synthesis, accounting for 0.02% of worldwide greenhouse emissions. The CO2 cycloaddition to ethylene and propylene oxides is an important class of reactions due to the versatile nature of the corresponding organic carbonates as chemical feedstocks. We report that these reactions can be catalyzed by ZIF-8 (Zeolitic Imidazole Framework-8) in the absence of solvent or co-catalyst and in mild conditions (40 °C and 750 mbar). In situ infrared spectroscopy places the onset time for ethylene and propylene carbonate formation to 80 and 30 min, respectively. Although there is low catalytic activity, these findings suggest the possibility to cut the CO2 emissions from epoxides production through their direct conversion to these highly valuable chemical intermediates, eliminating de facto energetically demanding steps as the CO2 capture and storage.

Modeling Metal Influence on the Gate Opening in ZIF-8 Materials

“…Zeolitic imidazolate frameworks (ZIFs) are a class of materials whose structure is obtained by connecting unitary metal centers through organic molecules containing imidazolate rings. − The bond between the metal and a nitrogen atom on the imidazolate ring gives these materials a significant thermal, mechanical, and chemical stability. − This, together with their porous nature, places them among the most studied materials for various applications and in particular for the separation of both gases and liquids − as well as for catalysis. , The ZIF-8 (Zn­(mIm) 2 , mIm = methylimidazolate) ,,, material has been extensively investigated. Its porous structure is constituted by spherical micropores (diameter of 11.6 Å) connected through four-membered (4MR) and six-membered rings (6MR).…”

Effect of MAF-6 Crystal Size on Its Physicochemical and Catalytic Properties in the Cycloaddition of CO2 to Propylene Oxide

“…The lower yield of PC is not in agreement with the highest strength of basic sites of MAF-5 in comparison with MAF-6 (Table 4) which are important in reaction mechanism. According to a reaction mechanism (Scheme S1, Supporting Information), the Lewis acidic center interacts with the oxygen atom of the epoxide, while the Lewis basic site activates a CO 2 molecule [65,66]. Investigation of cycloaddition of CO 2 to PO by DRIFT spectroscopy pointed that the Zn-N couples (LAS-BS) are formed by the defect sites where proceeds ring-opening step and CO 2 activation [66].…”

“…According to a reaction mechanism (Scheme S1, Supporting Information), the Lewis acidic center interacts with the oxygen atom of the epoxide, while the Lewis basic site activates a CO 2 molecule [65,66]. Investigation of cycloaddition of CO 2 to PO by DRIFT spectroscopy pointed that the Zn-N couples (LAS-BS) are formed by the defect sites where proceeds ring-opening step and CO 2 activation [66]. The addition of [n-Bu 4 N]Br to catalyst accelerates the ring-opening step due to the nucleophilic attack to C1 atom of epoxide and producing an intermediate (Scheme S1, Supporting Information).…”

Visible-Light-Driven Photocatalytic Coupling of Benzylamine over Titanium-Based MIL-125-NH2 Metal–Organic Framework: A Mechanistic Study

“…It is possible to modify separately the inorganic and the organic building units to tailor the material for a specific use. MOFs have been already reported as efficient catalyst and photocatalysts for several reactions, [15][16][17][18][19][20] and in particular for imine synthesis. 10,[21][22] .…”

“…It is possible to modify separately the inorganic and the organic building units to tailor the material for a specific use. MOFs have been already reported as efficient catalysts and photocatalysts for several reactions − and in particular for imine synthesis. ,, Photocatalytic oxidation of amines to imines is particularly appealing because it requires reaction temperature close to room temperature. Moreover, it has been recently proposed to be combined with water splitting for hydrogen production as a way to increase the valuable products of the reaction. , Titanium-based MOFs have been reported as photocatalysts for many reactions − due to their high thermal and chemical stability.…”