A novel heterogeneous catalyst was synthesized by immobilization of a carboxylic acid-and imidazolium-based ionic liquid on the mesoporous MIL− 101(Cr) (MIL−101(Cr)−TSIL) and used to convert abundant, nontoxic, economical and renewable CO 2 gas to cyclic carbonates without the need for a cocatalyst or a solvent. The catalyst was characterized in detail by multiple techniques such as XRD, TEM, SEM, EDX, DR-FTIR, solid-state NMR, as well as N 2 and CO 2 adsorption measurements. The catalytic properties were studied by varying different parameters including amount of catalyst and epoxide, temperature, pressure, and reaction time. Under optimal conditions (100 mg catalyst, 15 mmol epoxide, 2.0 MPa CO 2 pressure, 110 °C and 2 h reaction time) various cyclic carbonates were obtained with high yield and selectivity. MIL−101(Cr)−TSIL catalyst displayed good thermal stability and could be reused after simple separation without a significant decrease in its catalytic activity. Due to synergetic effect of the hydrogen bond from the carboxylic acid group for activation of the C−O bond of the epoxide, adsorption of CO 2 by the imidazolium moiety, and high concentration of CO 2 around the task specific ionic liquid (TSIL), arisen from the mesoporous framework, MIL−101(Cr)−TSIL is a highly effective catalytic system for the solvent-free cycloaddition of CO 2 with epoxide.

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An imidazolium-based ionic liquid was embedded into MIL-101­(Cr) via coordinate and covalent bonds to synthesize heterogeneous catalysts for efficient CO2 capture at low pressure and CO2 fixation with epoxides. In MIL-IL­(A), the ionic liquid was coordinated to Cr centers, while in MIL-IL­(B), the ionic liquid was attached to MIL-101­(Cr) via a covalent bond. These two materials were used for CO2 capture at p/p 0 = 0.033 and 0 °C. The results showed that the CO2 absorbing capacity for MIL-IL­(A) and MIL-IL­(B) is 5.46 and 7.84 times higher than that of the parent MOF, respectively. The ionic liquid loading was measured by IC, CHN, and thermogravimetric analysis (TGA). Furthermore, the catalytic activity of both catalysts was checked in the cycloaddition of CO2 to epoxides in the absence of any cocatalyst and under solvent-free conditions. A firm bond between the ionic liquid and the framework in MIL-IL­(B) made it a recyclable heterogeneous catalyst for CO2 fixation with epoxides. The analytical techniques confirmed the grafting of ionic liquid on the MOF structure, and the framework remained intact after 5 cycles in the cycloaddition of CO2 to styrene epoxide.

Hierarchical H-form ZSM-5 (h-ZSM-5) was synthesized and successfully functionalized with imidazolium-based ionic liquids for solvent-free insertion of carbon dioxide to epoxides and synthesis of cyclic carbonate. Tetrapropyl ammonium hydroxide and polyurethane foam were used as soft and hard templates, respectively, to introduce mesoporosity in the structure. The synthesized hierarchical H-form ZSM-5 provided a large surface area for covalent attachment of imidazolium-based ionic liquids to produce h-ZSM-5-IL. The successful synthesis of the new catalyst was confirmed by X-ray diffraction, Fourier transform infrared spectroscopy, the Brunauer–Emmett–Teller method, and scanning electron microscopy and utilized for the insertion of carbon dioxide to epoxides and production of cyclic carbonate under solvent-free conditions. High conversion and selectivity for the synthesis of cyclic carbonate and recovery of the catalyst for five consecutive times without loss of catalytic activity are the advantages of this newly synthesized catalyst.

A novel heterogeneous nanocatalyst was established by supporting molybdenum (VI) on Zr 6 nodes in the structure of the well-known UiO-66 metalorganic framework (MOF). The structure of the UiO-66 before and after Mo (VI) immobilization was confirmed with XRD, DR-FTIR and UV-vis spectroscopy, and the presence and amount of Mo (VI) was identified by X-ray photoelectron spectroscopy and inductively coupled plasma atomic emission spectroscopy. TEM imaging confirmed the absence of Mo clusters on the MOF surface, while SEM confirmed that the appearance of the MOF has not changed upon immobilizing the Mo (VI) catalyst. BET adsorption measurements were used to confirm the porosity of the catalyst. The catalytic activity of this heterogeneous catalyst was investigated in oxidation of sulfides with H 2 O 2 in acetonitrile and oxidative desulfurization of dibenzothiophene. Easy work up, convenient and steady reuse and high activity and selectivity are prominent properties of this new hybrid material.