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Fixing the greenhouse gas CO2 through epoxide helps to mitigate worldwide ecological troubles. The applications of metal‐free and solvent‐free catalysts remain a challenge for CO2 catalytic conversion. In this work, an array of quaternary ammonium salts derived from polyethyleneimine with hydroxyl groups ([PEI‐GDMAB‐Cn]Br) were constructed by the reaction of branched PEI with a molecular weight of 10000 and glycidyl alkyl dimethylammonium bromide. A range of experiments were designed to demonstrate that [PEI‐GDMAB‐Cn]Br can be considered as a valid metal‐free and solvent‐free homogeneous catalyst for the CO2‐epoxide cycloaddition reaction. Among of [PEI‐GDMAB‐Cn]Br, [PEI‐GDMAB‐C18]Br catalyzed the model reaction of CO2 and epichlorohydrin under optimized reaction conditions (T=80 °C, 1.0 atm CO2, catalyst 1 mol%, ECH 15 mmol, 16 h) and the conversion achieved at 97.5 %. Moreover, the catalyst exhibited stable reusability and broad substrate applicability, which was used in the following cycle succinctly, because of self‐separated properties by temperature control. The [PEI‐GDMAB‐C18]Br catalyzed reaction process was detected as a pseudo‐first‐order reaction after kinetic studies and an Ea was calculated to be 50.65 kJ/mol. A combinatorial catalytic mechanism of hydrogen bonding and bromide ions is suggested to explain the remarkable catalytic performance of this bifunctional catalyst. [ABSTRACT FROM AUTHOR]

• Co-Salen complexes containing different groups and bearing potassium iodide (KI) complexed with crown ether (K@SCs) were prepared. • Salen derivative organic polymer as heterogeneous catalyst for CO 2 cycloaddition reaction. • Alkali metal halides and Lewis acids have good synergistic effects in catalytic reactions. Metallosalen presents very important applications in both homogenous and heterogeneous catalysis. Correspondingly, porous polymeric metallosalen combined with the performance of organometallics and heterogeneous polymers possess potential in CO 2 fixation reactions. Herein, a family collection of K@SCs were conceived and obtained by combining cobalt-salen complexes with different groups and diaminobenzene-18-crown-6 complexed with KI, which allows multiphase catalytic immobilization of CO 2 to epoxides. Catalyst K@SC-3 can fix CO 2 into a variety of substituted epoxides in >90% yields to the corresponding cyclic carbonates in co-catalyst-free and solvent-free conditions. Furthermore, K@SC-3 can be recovered and reused at least six times by simple centrifugal separation, demonstrating superior stability. The kinetics experiments were also carried out at varied temperatures catalyzed by K@SC-3. It is concluded that a first-order equation of epoxide was proved and the activation energy was calculated to be 27.13 KJ/mol. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • The SP-COPs exhibited high catalytic efficiency of CO 2 conversion and excellent I 2 adsorption capacity. • The synergistic mechanism of CO 2 conversion was proved by experimental and kinetics. • The iodine adsorption kinetic process was described. The fixing reactions of carbon dioxide with epoxides will not only help to ameliorate the problem of global warming, but also facilitate the synthesis of cyclic carbonates that have a multitude of applications. Herein, a new sequence of Salen cobalt complexes adjusted with different counterions and interconnected with pyrene group were synthesized through Friedel–Crafts alkylation, which were served as conjugated organic polymers (SP-COPs) for taking advantage of catalytic CO 2 fixation reactions and iodine adsorption. Further characterizations were carried out through FT-IR, UV, TGA, and SEM to comprehend the intact structure, thermal stability, morphology and other physical and chemical properties. All materials exhibited effective catalytic performance, and in particular, SP-COP-1 with co-catalyst of TBAI achieved 96.2% conversion under ultra-mild conditions. The E a was obtained to be 46.4 kJ·mol−1 by performing kinetic experiments at different temperatures by fitting the experimental data. The performance of iodine vapor adsorbed by these materials at ambient pressure of 75°C reached 2.8 g·g−1, 2.2 g·g−1 and 2.6 g·g−1 respectively, and the adsorption process is describable in terms of pseudo-first-order and pseudo-second-order adsorption kinetics. [ABSTRACT FROM AUTHOR]

• The Tröger base analogue coordinated with potassium iodide and containing crown ether CATB-KI was fabricated. • The acidified CATB-KIs shown high catalytic efficiency to cyclic carbonates. • The synergistic mechanism has been proved in terms of experimental results and calculation of dynamics. Tröger's bases (TB) containing two steric nitrogen atoms, are alternated as building block for constructing molecular acceptors to form covalent bonds with acids, making TB a promising catalyst. Herein, TB analogs fabricated with crown ethers were knitted by condensation reaction and combined with potassium iodide as a brand-new catalytic system (CATB-KIs), which were characterized using FT-IR, 13C CP MAS NMR, SEM, TGA, and XPS spectroscopy respectively. The generated CATB-KIs exhibited excellent performance for CO 2 fixation reaction with epoxides to produce cyclic carbonates under mild conditions, and the catalytic activity could be further improved by coordinating with acids beforehand, in which HBr performs fascinated activity. After 12 h, the corresponding cyclic carbonate from epichlorohydrin with 95.1% yield was detected at mild conditions with solvent-free in the presence of CATB-KI-2 and HBr. A series of terminal epoxides were converted into desired cyclic carbonates with desirable yields. The catalyst could be recovered successfully and reused six times without significant loss of activity. Finally, dynamics study on catalytic mechanism has been accomplished and the activated energy was calculated as 72.1 kJ/mol. A synergistic catalytic mechanism of hydrogen bonding and I anion has been proposed to account for the excellent catalytic activity of this catalysts. [Display omitted] [ABSTRACT FROM AUTHOR]