Sonochemical synthesis of MOF-235 and polyvinylpyrrolidone (PVP)-assisted phase transformation to MIL-53(Fe)

Abstract

Metal–organic frameworks (MOFs) have garnered significant interest due to their diverse applications in industry, synthetic chemistry, and biomedicine. However, achieving MOF materials through fast and facile methods remains challenging due to the frequent formation of mixed phases, which can lead to misassignment of phase structures and complicated characterization. To overcome these challenges, the development of alternative synthesis strategies is required. In this study, a rapid and straightforward sonochemical method was employed to synthesize MOF-235 as an iron-based MOF. During the synthesis, polyvinylpyrrolidone (PVP) was applied as a surfactant to influence the physicochemical properties of MOFs. Surprisingly, the results demonstrated that the combination of ultrasound and PVP not only modified the physicochemical properties of MOFs but also induced a phase transformation from MOF-235 to MIL-53(Fe), resulting in a more stable structure within a short period of synthesis and at a constant temperature. Notably, this is the first report identifying PVP as a surfactant capable of driving a structural phase transition in MOF-235. This strategy promoted surface modification, changed textural properties and resulted in more uniform particle distribution. These findings provide a promising route to achieve better phase control in MOF synthesis and offer insights into surfactant-assisted phase engineering.