Green synthesis of polyureas from CO2 and diamines with a functional ionic liquid as the catalyst

Abstract

A series of ionic liquids (P_4,4,4,6BF₄, P_4,4,4,6Triz, as well as the newly prepared anion dual-functionalized amino-triz IL P_4,4,4,6ATriz, etc.) were prepared, and their catalytic performance was tested in the synthesis of polyureas from CO₂ and diamines. Under the optimized reaction conditions, good to excellent yields of various polyureas were achieved with different diamines over P_4,4,4,6ATriz catalyst. It can be found that the catalytic performance is essentially consistent with the basicity of ILs (as determined by TPD method). The solid products were characterized extensively by ¹³C NMR, FT-IR, XRD, DSC and TGA. From these results, it could be concluded that the solid products based on diamines and CO₂ have the polyurea structure with the urea linkage and connected by hydrogen bonds, which resulted in their high resistance to solvents and excellent thermal stability.