A new Brønsted acid MIL‐101(Cr) catalyst by tandem post‐functionalization; synthesis and its catalytic application

Abstract

A new heterogeneous Brønsted solid acid catalyst was prepared by tandem post‐functionalization of MIL‐101(Cr) and utilized for acetic acid esterification and alcoholysis of epoxides under solvent‐free conditions. First, MIL‐101(Cr) was functionalized with pyrazine to achieve MIL‐101(Cr)‐Pyz. Afterwards, the nucleophilic reaction of MIL‐101(Cr)‐Pyz with 1,3‐propane sultone and next acidification with diluted sulfuric acid gave MIL‐101(Cr)‐Pyz‐RSO 3 H Brønsted solid acid catalyst. Various characterization methods such as Fourier transformation infrared (FT‐IR) spectroscopy, X‐ray diffraction (XRD), elemental analysis (CHNS), X‐ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), energy‐dispersiveX‐ray(EDX) spectroscopy, thermal analysis (TGA/DTA), acid–base titration, and N 2 adsorption/desorption analysis were employed to fully characterize the prepared catalyst. The catalyst showed high activity compared to unmodified MIL‐101(Cr) in both catalytic acetic acid esterification and alcoholysis of epoxides. It can also be readily isolated from the reaction mixture and reused three times without major decrease in its activity.