Zwitterionic cellular polymer enabled reductive fixation of CO2 for N-methylation of amines

Using heterogeneous catalysts to promote the construction of the C–N bond between amines and CO2 under mild conditions is a challenge yet. Herein, we synthesized a novel zwitterionic polymer (PDDC) with a cellular structure via self-complexation of copolymer bearing both quaternary ammonium cation and carboxylate anion. PDDC was employed as a recyclable catalyst for N-methylation of atmospheric CO2 and various amines with hydrosilane as a reductant, affording more than 17 ​N-methylamines in good to excellent yields (up to 99%) under mild conditions. The behavior of PDDC in the reaction medium was disclosed by using a dynamic light scattering study, revealing that the decreased hydraulic radius of particle size contributes to exposing more active sites and increasing reaction activity. Utilizing a series of designed experiments and density functional theory calculations uncovered the crucial role of the prepared zwitterionic polymer during the reaction procedure of CO2 conversion.