Facile Construction of Carboxyl-Functionalized Ionic Polymer towards Synergistic Catalytic Cycloaddition of Carbon Dioxide into Cyclic Carbonates

Abstract

The development of bifunctional ionic polymers as heterogeneous catalysts for effective, cocatalyst- and metal-free cycloaddition of carbon dioxide into cyclic carbonates has attracted increasing attention. However, facile fabrication of such polymers having high numbers of ionic active sites, suitable types of hydrogen bond donors (HBDs), and controlled spatial positions of dual active sites remains a challenging task. Herein, imidazolium-based ionic polymers with hydroxyl/carboxyl groups and high ionic density were facilely prepared by a one-pot quaternization reaction. Catalytic evaluation demonstrated that the presence of HBDs (hydroxyl or carboxyl) could enhance the catalytic activities of ionic polymers significantly toward the CO2 cycloaddition reaction. Among the prepared catalysts, carboxyl-functionalized ionic polymer (PIMBr-COOH) displayed the highest catalytic activity (94% yield) in the benchmark cycloaddition reaction of CO2 and epichlorohydrin, which was higher than hydroxyl-functionalized ionic polymer (PIMBr-OH, 76% yield), and far exceeded ionic polymer without HBDs groups (PIMBr, 54% yield). Furthermore, PIMBr-COOH demonstrated good recyclability and wide substrate tolerance. Under ambient CO2 pressure, a number of epoxides were smoothly cycloadded into cyclic carbonates. Additionally, density functional theory (DFT) calculation verified the formation of strong hydrogen bonds between epoxide and the HBDs of ionic polymers. Furthermore, a possible mechanism was proposed based on the synergistic effect between carboxyl and Br− functionalities. Thus, a facile, one-pot synthetic strategy for the construction of bifunctional ionic polymers was developed for CO2 fixation.

Synthesis of Metal-Free Benzimidazole-Based Catalysts and its Application in CO2 Cycloaddition

“…The XPS survey spectra showed the presence of C, N, O, and Br elements in both BZI-NH 2 and BZI-OH. In the BZI-NH 2 , a small amount of oxygen may be attributed to the presence of hydrophilic -NH 2 in the polymer network (Chen et al 2022).…”

Optimization and kinetics of crown ether-based hydroxyl-rich organic polymers for sustainable CO2 fixation and iodine vapor adsorption

“…17,18 While the high free energy of epoxides can counterbalance the high thermal stability of CO 2 in the atmosphere, certain catalysts make the fixation of CO 2 onto epoxides thermodynamically advantageous. The current state of the art involves the development of a wide range of catalysts such as ionic liquids (ILs), 19–21 metal complexes, 22–27 metal organic frameworks (MOFs), 28–32 supported catalysts, 33–37 covalent organic frameworks (COFs), 38–40 and porous organic polymers (POPs), 41–47 each possessing distinct structures and functions, to efficiently facilitate this reaction. Among these, POPs exhibit unique CO 2 conversion and I 2 capture properties, due to their high intrinsic specific surface area, controllable pore size, synthetic versatility, exceptional physicochemical stability, and facile functionalization for creating metal-active centers.…”