CaO nanoparticles incorporated metal organic framework (NH2-MIL-101) for Knoevenagel condensation reaction

Porous materials based on NH2-MIL-101(Cr) MOF and their hierarchical acid-base composite with non-precious CaO was successfully prepared using a one-pot scalable hydrothermal approach. The composites were characterized by XRD, FTIR, UV-vis, 1HNMR, TGA, N2 adsorption-desorption isotherms, HRTEM and FESEM. The quantitative assessment of the basic sites was performed by benzoic acid titration. The results reveal that there is no remarkable structural alterations in the NH2-MIL-101(Cr) after incorporation of CaO. Raising the CaO content boosted the strength of and content of Lewis basic sites from 0.31 to 1.34 mmol g-1 due to the incorporation with CaO (0.04). Knoevenagel condensation reactions were performed as the probe reactions over the CaO/NH2-MIL-101(Cr) catalysts. Both basic and acidic sites potentially boosted the reaction. Pure NH2-MIL-101(Cr) display the catalytic conversion in the reaction (11%) which could be attributed weak basic sites on the NH2-MIL-101(Cr) framework. However, the conversion (%) was potentially increased over NH2-MIL-101(Cr) loaded with various content of CaO. The highest performance of (99%) conversion was achieved for (0.04) CaO/NH2-MIL-101(Cr) catalyst. Exceptional conversion above 90% have been obtained for benzaldehyde derivatives both withdrawing and donating electron moieties. The composites can be recycled in four runs with a very small loss in performance. Furthermore, the composites produced tend to be feasible for various catalytic processes, exploring new avenues to produce of novel inorganic and organic composite materials as heterogeneous catalysts. (c) 2021 The Author(s). Published by Elsevier B.V. on behalf of King Saud University. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Automated summary

Porous materials based on NH2-MIL-101(Cr) MOF and their hierarchical acid-base composite with non-precious CaO were prepared successfully. The introduction of CaO increased the number and strength of basic sites, leading to improved conversion rates in catalytic reactions. These composites showed recyclability and potential applications in various catalytic processes.