Green synthesis of isosorbide-based polycarbonate via dimethyl carbonate by dual imidazolate ionic liquid catalyst

Synopsis: A green synthesis pathway for isosorbide-based polycarbonate was developed via one-step melt polycondensation of dimethyl carbonate. • Green synthesis of bio-based polycarbonate via one step melt polycondensation of isosorbide and dimethyl carbonate. • The strong electrophilicity/nucleophilicity and weak ion-pair interaction of dual imidazolate ionic liquid enhance the catalytic efficiency. • A mechanism of synergetic catalysis of cation–anion promoting chain growth was proposed. Addressing the increased demand for the development of bio-based polymers from renewable resources, a pathway for synthesizing poly(isosorbide carbonate) (PIC) via melt polycondensation catalyzed by ionic liquid (IL) was proposed from CO 2 -based dimethyl carbonate (DMC) and bio-based isosorbide (ISB) as reactants. 1-Ethyl-3-methylimidazolium imidazolate ([Emim][Im]) with imidazole acted as both an anion and a cation was designed and the highest activity with an ISB conversion of 98 % and PIC molecular weight of 52600 g·mol −1 was achieved for the PIC synthesis compared to other catalysts with single imidazole cation or anion. High catalytic activity of [Emim][Im] can be attributed to its exceptionally high cationic electrostatic potential (+53.05 kcal/mol) and remarkably low anionic electrostatic potential (−76.12 kcal/mol), which collectively result in the strongest relative electrophilicity and nucleophilicity. Furthermore, the reduced electrostatic complementarity weakens the ion-pair interactions between the cation and anion, thereby enhancing the accessibility of active sites during the catalytic process. This process will promote the sustainable production of bio-based polymers.