To measure the thermal stability of PILs-XSS, TG curves were recorded in flowing dry N2. As shown in Figure 5, the initial weight loss at 293.4 °C was 8.9%, which was due to the adsorption of organic solvents and water on the surface of the catalyst PILs-XSS during washing. A complete loss of all covalently attached organic structures was observed in the temperature range of 293.4–481.3 °C [33], and the final amount of remaining organic components was approximately 12.9% of the total solid catalyst. Therefore, PILs-XSS is thermally stable below 293.4 °C, proving the feasibility of this catalyst as a solid catalyst basis for catalyzing CO2 to DMC by one-pot method.
Fig. 5 TG analysis of PILs-XSS
3.2 The synthesis of DMC by one-pot method
3.2.1 Hydrocarbon spectrum analysis products
To detect the presence of dimethyl carbonate in the product, we performed nuclear magnetic resonance on the product after the reaction. Fig. 6 ( A ) was the 1HNMR spectrum, Fig. 6 ( B ) was the 13CNMR spectrum, and Fig. 6 ( C ) was the marker of the carbon vibration peak of each substance in the carbon spectrum. Combined with gas chromatography and nuclear magnetic resonance spectroscopy, all substances in the reaction were analyzed.