Fe(MIL-53) metal–organic framework as a facile and sustainable Lewis acidic catalyst for the one-pot synthesis of xanthene derivatives

Abstract

The catalytic application of the easily preparable Fe(MIL-53) MOF was demonstrated as a sustainable solid Lewis acidic catalyst in synthesising pharmaceutically essential xanthenes under mild conditions. The Fe(MIL-53) MOF catalyst was synthesised and characterised using various analytical tools such as PXRD, FTIR, SEM, TGA and ICP-OES. The presence of a high concentration of coordinatively unsaturated Fe³⁺ sites in Fe(MIL-53) can efficiently catalyse the formation of xanthenes in the presence of a catalytic amount (1.36 mg) of MOF using environmentally friendly, non-toxic and renewable ethanol as the medium. A series of substituted xanthenes were synthesised in good to excellent yield with wide functional group tolerance. The present methodology avoids the usage of any strong reagents and uses stoichiometric amounts of the catalyst. The catalytic comparison studies with other homogeneous and heterogeneous catalytic systems proved the efficiency of the present Fe(MIL-53) MOF catalyst. The hot-filtration test and reusability profile prove the stability and sustainability of this catalyst, which were also supported by PXRD, FTIR and SEM analysis of the reused catalyst.