Anchoring high-density cooperative catalytic sites within triethylenediamine-based ionic-liquid polymers via microenvironment modulation for efficient CO2 fixation.

Branched triethylenediamine-based polymers with high-density ionic sites were synthesized by self-polymerization strategy, and the cooperative catalytic sites facilitated the activation of epoxides thus boosting the CO 2 cycloaddition under mild conditions. [Display omitted] • Triethylenediamine-based ionic-liquid polymer was prepared via self-polymerization. • Branched structure and high-density cooperative catalytic sites were endowed. • Noteworthy yields of cyclic carbonates were achieved under mild conditions. • Synergistic interplay of tertiary N, quaternary ammonium, and Cl- were revealed. • Desirable reusability, epoxide universality, structural stability were attained. The precise microenvironment modulation of ionic sites to promote the catalytic performances of ionic-liquid polymers for CO 2 transformation has been highly attractive but rarely attempted. Herein, we reported a strategy to synthesize the triethylenediamine-derived ionic-liquid polymer (PDD-S) featured with branched structure and high site density (4.10 mmol·g−1). In distinct with the conventional synthetic routes, this method involved the pre-grafting and subsequent self-polymerization of ionic monomer, which suppressed the competitive reactions and broke the limitations of precursor selection, while ensuring the high content and even distribution of ionic sites within the polymeric framework. Furthermore, during CO 2 cycloaddition with epoxides we showed that these unique structural features allowed the adequate exposure of active sites under the dual effects of steric hindrance and charge repulsion. The PDD-S exhibited noteworthy catalytic performance, with a carbonate yield of 97.3 %, under the moderate conditions (100 °C, 4 h, 1 MPa) in the absence of any metal, co-catalyst, or solvent. Additionally, the desirable reusability, epoxide universality, and structural stability were also attained. The experiments combining with the activation energy and DFT theoretical calculations, attributed the synergistic interplay of tertiary N, quaternary ammonium, and Cl- anions to the acceleration of ring-opening process, thereby promoting the CO 2 transformation. The newly developed approach offers one perspective to the controllable fabrication of ionic-liquid polymers for catalytic fixation of CO 2. [ABSTRACT FROM AUTHOR]