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A series of bifunctional hexagonal MOFs have been successfully constructed by the introduction of various amine functional groups within the unsaturated Cu-based MOF, HKUST, to access amino-modified frameworks. The prepared compounds are cost-effective and display high chemical and thermal stability. They were effectually exploited as efficacious and superb heterogeneous catalysts in rapid and facile Knoevenagel condensation reactions for a variety of substrates containing different electron-donating and electron-withdrawing substituents with very high conversion, good reusability under mild conditions, and very short reaction time. The contaminant presence of Lewis acid and basic sites resulted in efficient condensation reactions by the prepared catalysts. [ABSTRACT FROM AUTHOR]

• Diamine functional groups were successfully incorporated into the CPM-5 frameworks. • This is the first report utilizing CPM-5 modified with diamine groups in cycloaddition reactions. • The Lewis acid-base dual sited of CPM-5-PhDA are active sites for fixation of CO 2 to cyclic carbonates. • The synthesized 3D porous catalyst exhibits high catalytic activity for cycloaddition of CO 2 with epoxide in the absence of co-catalyst and solvent. In the present work, functional diamine groups into indium frameworks to synthesize cyclic carbonates from CO 2 and epoxides with efficient catalytic activity in the absence of co-catalyst and solvent are reported for the first time. Crystalline porous materials (CPM)-5 modified with 1,2-phenylene diamine and ethylene diamine (CPM-5-PhDA and CPM-5-EDA), were prepared using a post-synthetic modification (PSM) method. The properties of the modified CPM-5 were characterized by powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), N 2 -adsorption, scanning electron microscopy (SEM), CO 2 adsorption, and temperature programmed desorption TPD methods. The presence of diamine groups as basic sites and indium Lewis acid sites in the framework structure were desirable for high catalytic activity. For a given catalyst weight, CPM-5-PhDA was the best candidate to appear with great catalytic activity and selectivity for the cycloaddition reaction at 100°C and 1 MPa CO 2 under co-catalyst and solvent free conditions. CPM-5-PhDA also was found to afford large and bulky epoxides. The catalyst can be easily separated and reused five times without any decline in activity. [Display omitted] [ABSTRACT FROM AUTHOR]

In this work, three bifunctional metal‐organic frameworks (MOFs) were constructed through the introduction of various linear amine functional groups within MIL‐101(Cr). The unsaturated chromium metal center was incorporated with three various ligands including ethylene diamine, diethylene triamine, and diamino butane. The resultant prepared MOFs contain unsaturated chromium centers as Lewis acidic centers and amine groups as basic sites. The contemporary existence of basic and acidic centers allowed prepared bifunctional compounds to be highly effectual heterogeneous catalysts for chemical fixation of CO2 with epoxides, affording cyclic carbonates, under relatively mild conditions and in the absence of either solvent or cocatalyst. High tendency of prepared structures toward CO2 adsorption followed by speeding up the nucleophilic attack resulted in gaining excellent conversion, selectivity, and activity for large epoxide as well as bulky ones. The synthesized catalyst outperforms other reported heterogeneous catalysts. High conversion, TON, recyclability, and mild reaction conditions are some distinctive characteristics of the bifunctional synergetic catalysts. [ABSTRACT FROM AUTHOR]

Metal-organic frameworks (MOFs) as acid catalysts provide active sites with particularly appropriate for glycerol conversion. In this study, Mil-118-SnO2 was synthesized by doping SnO2 quantum dots with Mil-118. The SnO2 quantum dots were formed through the epoxide-assisted precipitation route as a proton scavenger and following ring-opening that drives hydrolysis and, ultimately, condensation of the hydrated metal. The Mil-118-SnO2 was used as a catalyst for the production of five-member (2, 2-dimethyl-1, 3-dioxolane-4-methanol) and six-member (2,2-dimethyl-dioxane-5-ol, (II)) cycles. The results revealed a higher conversion rate and selectivity for Mil-118-SnO2 than for Mil-118. An increase was observed in conversion and selectivity, which was related to the improvement of the acidic properties of Mil-118 after doping SnO2 quantum dots. The experiments were conducted under mild conditions, producing a 40% increase in conversion and selectivity. This catalyst could be reused up to five times with 97% selectivity during a cycle. Glycerol is produced as the key byproduct in the transesterification process. The as-synthesized Mil-118-SnO2 then was used as a heterogeneous catalyst for the glycerol conversion to solketal. The experiments were carried out under mild conditions, which produced a 40% increase in conversion and selectivity. [ABSTRACT FROM AUTHOR]

Nucleophilic substitutes provide a new platform to design and synthesize novel bifunctional heterogeneous catalysts for carbon dioxide cycloaddition reaction with epoxides. Herein, in this work, UMCM-15 was fabricated and modified with various nucleophilic ligands containing bromine, amine and hydroxyl functional groups. The resultant prepared compounds were utilized as bifunctional synergetic catalysts for the chemical fixation of carbon dioxide. The catalysts can efficiently catalyze epoxides and carbon dioxide under relatively mild conditions in the absence of co-catalyst and solvent. The contemporaneous presence of Lewis acid and basic centers in the framework resulted in high catalytic activity and turnover number (TON) value for the production of cyclic carbonates compared to other reported compounds indicating superiority of the synthesized catalysts. Among diverse applied bifunctional catalysts, bromine-functionalized frameworks exhibited the highest catalytic performance owing to the presence of multiple electron pairs and the great tendency to donate electron pairs. [Display omitted] • Diverse nucleophilic functional groups were successfully modified on an unsaturated Zn-based MOF. • The novel modified framework was utilized as superior catalysts in the aspect of CO 2 cycloaddition reactions. • Cycloaddition reactions accomplished in the absence of either co-catalyst or solvent under relatively mild condition. • This is the first report utilizing and comparing various nucleophilic functional groups as co-catalyst in cycloaddition reaction. • The prepared 3D porous structures display much higher activity and TON than other previously reported catalysts. • The catalyst could be reused. [ABSTRACT FROM AUTHOR]