A facile one-step synthesis to ionic liquid-based cross-linked polymeric nanoparticles and their application for CO2 fixation

Abstract

Highly cross-linked polymeric nanoparticles (CLPNs) were prepared via a facile one-step synthesis, and these nanoparticles are effective catalysts for CO₂ cycloaddition with epoxides. In this study, CLPNs were synthesized by radical copolymerization of 4-vinylbenzyl-tributylphosphorous chloride (PIL) and ethylene glycol dimethacrylate (EGDMA) in selective solvent, such as C1∼C5 alcohols. The results revealed that spherical nanoparticles with the mean diameter range of 10–100 nm could be prepared in these alcohols, and the size of the CLPNs could be facilely tuned by the feed ratio of EGDMA to PIL. The CLPNs were characterized using dynamic light scattering, scanning electron microscopy, transmission electron microscopy, atomic force microscopy, thermogravimetric analysis, atom absorbance spectrometry, and Fourier transform infrared spectroscopy techniques. In addition, CLPNs can be exploited as highly active and selective catalyst for the cycloaddition of CO₂ to epoxides. The effects of parameters, such as reaction temperature, pressure, reaction time, and catalyst amount, on the cycloaddition reaction were investigated. As a result, excellent yield (100%) and selectivity (100%) of cyclic carbonates could be achieved under mild conditions (0.1 g CLPNs, 3.0 MPa CO₂, 140 °C and 3 h) without the addition of any solvents or co-catalysts. Unexpectedly, the CLPNs could be dispersed in the products homogeneously, which resulted in the extremely high activity and selectivity. At the same time, the CLPNs could be easily separated by filtration after pouring the reaction mixture into toluene. CLPNs could be recycled six times with less than 1.5% loss of catalytic activity.