Thiol–ene click reaction: a new pathway to hydrophilic metal–organic frameworks for water purification†

Post-synthetic modification (PSM) is a useful strategy to introduce new functional groups to metal–organic framework (MOF) structures in order to tune their properties for different applications. One of the methodologies used for PSM of MOFs is click chemistry known for their high reaction efficiency and good compatibility with various functional groups. Herein, we report the first PSM example of a thiol-functionalized MOF. Pores surface of the Zr-MSA MOF (based on Zr and mercaptosuccinic acid (MSA)) was decorated with short poly (ethylene glycol) (PEG) chains using click chemistry. Mono or di acrylate functional PEG were attached to the MOF pore walls either using UV irradiated thiol–ene click or Michael addition thiol–ene click reactions. The use of mono-functionalized PEG resulted in the formation of colloidal stable particles while the use of di-functionalized PEG led to a cross-linked network. The properties of PEG modified Zr-MSA were fully characterized using various structural, textural and morphological techniques. The sample containing the highest PEG content was then used for the removal of mercury, Hg(II); chromium, Cr(VI) and rhodamine B (RhB) from water. Results suggest that the hybrid material was able to capture these pollutants while maintaining a good colloidal stability and hydrophilicity. Therefore, click chemistry has been proved as an efficient strategy for the surface modification of MOF particles with low molecular weight polymers.