Ferrocene-containing thixotropic molecular gels: creation and a novel strategy for water purification

Low-molecular-mass gelators and relevant molecular gels have been employed for water purification owing to their convenience and efficiency, but the process is time consuming due to low extraction efficiency originated from limited contact of the two phases. In this work, two novel di-cholesterol-based gelators, 1 and 2, with a ferrocenyl unit were synthesized and the gels based on 2 possess a smart thixotropic property. In particular, 2/heptane gel, the shear force induced phase transition is fast (within seconds) and fully reversible without the need of heating-cooling cycle. Based upon the thixotropic molecular gel, a novel separation strategy, which combines the great efficiency of liquid-liquid extraction and the convenience of liquid-solid separation, has been successfully conducted for removing iodine from wastewater. It was demonstrated that iodine was removed within several minutes and the extraction efficiency (72%) was the same with the one using corresponding liquid. Furthermore, 2/heptane gel is also responsive to chemical oxidation and variation in temperature. FTIR, NMR, CD and XRD studies revealed that helical fibers were formed via intermolecular hydrogen bonding and van der Waals interaction. It is believed that the results presented in this work are of importance for extending real-life applications of molecular gels.