Fig. 2 FT-IR spectra : ( a ) 1-vinylimidazole, ( b ) 1,2-dibromoethane, ( c ) PILs-XSS, ( d ) N, N ’ -methylenebisacrylamide

3.1.2 BET-BJH analysis of PILs-XSS

BET-BJH analysis was performed on the structure of the sample, as shown in Figure 3, showing the specific surface area and pore size test curve of the material. First of all, the test chart of BET-specific surface area consists of two curves of adsorption and analysis. It can be seen from the figure that the adsorption hysteresis loop in the middle represents the type IV isotherm [29], and the specific surface area reaches 71.5m²/g, The average pore size of FILs-XSS is greater than 14.8 nm, which is an important sign of mesoporous materials [30]. The CO₂ molecule can fully contact with propylene oxide on the catalyst, which is very favorable for the first step of the reaction between CO₂ and propylene oxide, and the average pore size of PILs-FL has reached the basic requirement [31]. According to the situation analysis, PILs-FL has a high-quality specific surface area (71.5m²/g) and pore size (14.8nm), which can show good performance in the process of one-pot production of DMC.