Figure 6 . FT-IR exploration of the H2S addition reaction with styrene oxide (1a ) with [BDMAEEH][MeOAc] as the catalyst.
The recycling ability of PIL is of great significance for practical application in H2S conversion. The reuse of the catalyst in this system is very simple. Taking [BDMAEEH][MeOAc] as an example, 1.0 g styrene oxide (1a , 8.0 mmol) was fed into autoclave with 50 mol% loading of catalyst (1.0 g, 4mmol) at 30 ºC for 2.0 h. After the reaction, the catalyst can be separated from the system by water extraction without the participation of any organic solvent (four times extraction, the volume ratio of water to PILs is 1.0) (Figure S11 ). It is found that the lower phase after water extraction contains only two products (1b and 1c ) (based on NMR analysis, Figure S12 ), which can be easily separated from TLC. All the extracts were collected and combined, which can be used in the next circulation after drying in a vacuum line at 40 °C for half an hour. It is found that the conversion of styrene oxide (1a ) has no significant activity loss, demonstrating the good robustness and recyclability of PIL (Figure 7 ) after seven cycles (the first cycle was in the presence of fresh PILs).