Ship‐in‐bottle preparation of multi‐SO₃H functionalized ionic liquid@MIL‐100(Fe) for acid‐catalyzed ring‐opening of epoxides

Abstract

The fact that the homogeneous acid catalysts are usually separated difficulty than heterogeneous catalysts from the reaction media, the opportunity to combine the advantages of both homogeneous and heterogeneous catalytic systems by immobilizing ILs within the pores of a porous solid support host is an alternative method. In this research, a multi‐SO3H functionalized ionic liquid derived from hexamethylenetetramine (HMTA) and 1,3‐propane sultone was entrapped inside the pores of MIL‐100(Fe) through the ship‐in‐bottle method and utilized for heterogeneous acid‐catalyzed ring‐opening of epoxides under solvent‐free conditions. The physicochemical properties of prepared catalyst were fully elucidated by various methods. FT‐IR spectroscopy and elemental analysis approved the successful incorporation of modified groups within the MIL‐100(Fe) cavities. The concentration of acid sites was measured via the acid–base titration which exhibited the 0.9 mmol/g H+ in the catalyst structure. Also, thermogravimetric analysis (TGA) profile showed the loosing of modified groups at 300–600°C. Moreover, X‐ray diffraction (XRD) analysis showed that the MIL‐100(Fe) structure was retained after modification and nitrogen adsorption–desorption analysis (BET method) manifested the decrease in surface area caused by incorporation of ionic liquid. The fabricated catalyst exhibited high catalytic efficiency in methanolysis of styrene oxide (99% conversion in 3 h) under ambient conditions and used without a substantial drop in product yield in further rounds.

Sulfonic Acid-Grafted Hybrid Porous Polymer Based on Double-Decker Silsesquioxane as Highly Efficient Acidic Heterogeneous Catalysts for the Alcoholysis of Styrene Oxide

“…The catalytic activity is due to the difference in the diffusion abilities of these epoxides to interact with the active sites in a catalyst. The substrate with its smaller dimension can easily penetrate the pores and interact with active sites, but it is more difficult for the bigger substrate to reach the active sites. ,, …”

“…(Table , entry 3). In addition, the increase in the chain length is another reason for low conversion . Compared with 1,2-epoxyhexane, the conversion of cyclohexane oxide can reach 96% within 30 min (Table , entry 4), which is attributed to smaller steric hindrance and facile diffusion of cyclohexane oxide.…”

“…The substrate with its smaller dimension can easily penetrate the pores and interact with active sites, but it is more difficult for the bigger substrate to reach the active sites. 9,10,12 To confirm the superior catalytic activity of PCS-DDSQ-SO 3 H-1, Table 3 compares the catalytic activity of previous catalysts for methanolysis of styrene oxide with our catalyst. MIL-DABCO-SO 3 H and BAIL@MIL-100 (Fe) can produce 2methoxy-2-phenylethanol at room temperature, but a high catalyst dosage is the main reason to get high conversion;…”

“…Epoxides are used in medicine and agrochemicals as an important organic synthesis monomer; , nucleophiles such as alcohols can undergo nucleophilic addition reactions with them to generate β-alkoxyalcohols, which play an important role as pharmaceutical intermediates and fine chemicals . Traditionally, quite a few ring-opening reactions generally proceed using mineral acids as homogeneous catalysts. , However, this kind of catalyst has technical and environmental problems such as difficulties in post-treatment, corrosion of equipment, and sewage treatment, , while a heterogeneous catalyst as a kind of green catalyst can avoid the above problems, which has advantages of easy separation and good recyclability. − Recently, some heterogeneous catalysts, such as MOF, reduced graphene oxide, and silica, have been developed. − These catalysts still have some limitations, such as harsh reaction conditions and poor selectivity. Hence, it is crucial to create efficient catalysts for ring-opening reactions under mild conditions.…”