Toshiyasu S, Jun-Chul C, Hiroyuki Y (2007) Transformation of carbon dioxide. Nat Commun 6:1–15Īlvarez A, Bansode A, Urakawa A et al (2017) Challenges in the greener production of formates/formic acid, methanol, and DME by heterogeneously catalyzed CO 2 hydrogenation processes. Liu Q, Wu L, Jackstell R et al (2015) Using carbon dioxide as a building block in organic synthesis. Jessop P, Leitner W (2017) Green chemistry in 2017. McCollum D, Bauer N, Calvin K et al (2013) Fossil resource and energy security dynamics in conventional and carbon-constrained worlds. Jeong K, Hong T, Kim J (2018) Development of a CO 2 emission benchmark for achieving the national CO 2 emission reduction target by 2030. Schnoor JL (2014) Ocean acidification: the other problem with CO 2. Graphic AbstractĪ salen-based cationic covalent organic polymers (COP-Al) was used as a bifunctional catalyst for the cycloaddition reaction of CO 2 and epoxides with high activity under solvent-free and co-catalyst-free conditions. Notably, the heterogeneous catalyst still showed good activity and stability after five cycles. Due to its cooperative effect, a higher catalytic activity was found to exhibit 98.1% conversion of epichlorohydrin under optimized conditions (Initial pressure 1.0 MPa, 0.57 mol% catalyst of COP-Al, 90 ☌, reaction time 18 h, in the absence of a co-catalyst). In this polymer, aluminum acts as lewis acid site and bromine ion acts as nucleophile, cooperatively catalyzing the cycloaddition reaction of CO 2 and epoxides. The bifunctional cationic covalent organic polymer was investigated by various characterization technologies including PXRD, FT-IR, XPS, TG, SEM, EDS, N 2-adsorption and CO 2-adsorption. A cationic covalent organic polymer with bifunctional active site was synthesized, which was treated by N, N'-bis(5-bromomethylsalicylaldehyde)ethylenediamine (salen ligand) and tris(1H-imidazol-1-yl) triazine (TIT) in the presence of aluminum ethoxide.