Bypassing halide immobilization with cooperative polymers for the cycloaddition of atmospheric CO2 to epoxides

Atom-economic syntheses of cyclic organic carbonates by cycloaddition of CO2 to epoxides have risen to prominence among various approaches for CO(2 )fixation. In current literature, there is a general lack of recyclable fully heterogeneous organocatalytic systems which are active under mild conditions (T <= 60 degrees C, atmospheric pressure), and that do not involve elaborated synthetic steps for the synthesis of monomers or the coimmobilization of active sites such as hydrogen bond donors (HBDs) and halide nucleophiles. From the standpoint of cost reduction and sustainability, it is also highly desirable to obtain the catalytic materials from biobased sources, especially waste materials. To address such gaps in the literature, we disclose in this work that a lignin derivative (phenolated lignin, PL) can be used as HBD in cooperation with readily available ionic polymers to form recyclable heterogeneous catalytic systems able to carry out the target cycloaddition reaction under atmospheric pressure at 60 degrees C. This unprecedented approach allows the upcycling of readily available biobased materials for the mild synthesis of cyclic carbonates from CO2 and bypasses the need for elaborated synthetic procedures for the synthesis of coimmobilized HBD-halide systems. PL/QPBAE (quaternized polyaminoester) emerged among various PL/ionic polymer pairs as the most active and efficient catalyst. Such a result is justified through a spectroscopic and analytical investigation as an effect of the ability of PL and QPBAE to closely interact and disperse in the reaction medium, and of the higher flexibility of QPBAE compared to other ionic polymers such as quaternized polyvinylpyridine. The resulting catalytic pair can be used as an efficient recyclable system for the cycloaddition of CO2 to several epoxides under atmospheric conditions with a catalytic performance that compared very well to that of more complex oil-based state-of-the-art polymeric organocatalysts for the same reaction.