A series of carboxyl-group-functionalized imidazolium-based ionic liquids (CILs) were synthesized and grafted onto silica gel. The catalytic activity of the resulting heterogeneous catalysts toward the synthesis of cyclic carbonateviacycloaddition reactions of epoxide and CO₂ was studied. The effect on the reaction of the grafted ILs' structures and the reaction conditions such as reaction temperature, time, pressure, and the amount of catalyst used, were systematically investigated. For comparison, silica-grafted imidazolium-based ILs with and without hydroxyl groups were also used to catalyze cycloaddition reactions. The carboxylic acid group in the catalyst was demonstrated to have a synergistic effect with halide anions. A high yield of cyclic carbonates and excellent selectivity could be obtained under optimized conditions.

An approach employing a dual-porous metal organic framework as a catalyst for room temperature CO ₂ fixation via cyclic carbonate synthesis with high selectivity towards cyclic carbonates under solvent free conditions was demonstrated.

A novel heterogeneous one-component catalyst was developed by the covalent post functionalization of zeolitic imidazolate framework-90 (ZIF-90) with a pyridinium based ionic liquid (IL) to generate IL supported ZIF-90 (IL-ZIF-90). The synthesized catalyst has been characterized using a range of analytical, spectroscopic, and electron microscopy techniques followed by successful employment for the solventless cycloaddition of epoxides and CO₂ to yield cyclic carbonates under mild reaction conditions. The effects of reaction parameters like catalyst amount, reaction time, reaction temperature, and CO₂ pressure have been investigated. A reaction mechanism for the IL-ZIF-90 catalyzed PO–CO₂ cycloaddition has been proposed on the basis of density functional theory (DFT) calculations. The catalyst system was separable by centrifugation and reused four consecutive times successfully. In general, it can be suggested that IL supported porous metal organic frameworks (MOFs) may introduce a new class of highly porous catalyst species showing excellent CO₂ transforming capability.

Imidazolium-based ionic liquids with varied alkyl chain lengths bearing different anions (Cl⁻, Br⁻ and I⁻) were synthesized and immobilized onto the commercial silica surface (IMIS). These heterogeneous catalysts exhibited high catalytic activities and selectivities in the cycloaddition of carbon dioxide to allyl glycidyl ether (AGE). The immobilized ionic liquids with longer alkyl chain length and more nucleophilic anion showed higher activity. In particular, compared with pristine IMIS, zinc halide-combined IMIS (IMIS-Zn) with Cl⁻ exhibited an increased activity, while the IMIS-Zn with Br⁻ and I⁻ showed lower activity than IMIS itself. In addition, the textures of silica supports (surface area and average pore size) have a great impact on the catalytic activity owing to the substance-confined diffusion effects. The recycling experiments showed that the resulting heterogeneous catalysts exhibited good reusability.

A water-stable zinc-glutamate-MOF catalyst, prepared using a facile and eco-friendly method at room temperature, was employed for room temperature wet CO ₂ fixation reactions.