Carbon dioxide is the most abundant waste generated by anthropological processes. Its concentration in the atmosphere steadily increases, reaching 30 Gton.y-1; becoming a major environmental concern as it is primarily responsible for adverse global climate changes. In recent decades, the use of CO2 as a renewable feedstock has received attention from chemists to capture and transform it into high value products.

A series of HO-functionalized triazoles ionic liquids (1-10b) bearing different alkyl chains and counter-anions were evaluated as green, single component bifunctional catalysts for cycloaddition reaction of CO2 to epoxides. Ionic liquids 1-10b were all able to convert, selectively, PO into propylene cyclic carbonate (PCC), under the conditions described in Table 1.

These experiments motivated us to perform upscale reaction using 5b/PO (500 mmol) using 0.075 mol % of ionic liquid system which showed the highest TOF of this work (429 h-1) and 32 % of conversion at 1-hour reaction, increasing the reaction time to 10 hours, it was obtained 88 % of PC with TON = 1170 and TOF = 117 h-1, what shows that our cheap, easy to handle and easily synthesized catalyst is very active even in long periods and in very small catalytic loads compared to other organocatalysts. In optimal reactional conditions (25 mmol of epoxide, 140 °C, 30 bar of CO2, 1 hour), high conversions for a series of terminal epoxides were achieved using catalyst 5b. Moreover, the reaction using cyclohexene oxide achieved 85 % of conversion in only 6 hours.

In summary, HO-functionalized triazole-based ionic liquids are efficient single component, bifunctional, metal-free and solvent-free catalysts for CO2 fixation, presenting outstanding conversions, even in scale-up experiments