Ruthenium-Based Macromolecules as Potential Catalysts in Homogeneous and Heterogeneous Phases for the Utilization of Carbon Dioxide

Kaiprathu Anjali; Jayaraj Christopher; Ayyamperumal Sakthivel

doi:10.1021/acsomega.9b01741

Ruthenium-Based Macromolecules as Potential Catalysts in Homogeneous and Heterogeneous Phases for the Utilization of Carbon Dioxide

ACS Omega. 2019 Aug 8;4(8):13454-13464. doi: 10.1021/acsomega.9b01741. eCollection 2019 Aug 20.

Authors

Kaiprathu Anjali¹, Jayaraj Christopher², Ayyamperumal Sakthivel¹

Affiliations

¹ Inorganic Materials & Heterogeneous Catalysis Laboratory, Department of Chemistry, School of Physical Sciences, Central University of Kerala Kasaragod, Sabarmati Building, Tejawini Hills, Kasaragod 671316, India.
² Indian Oil Corporation Limited, R&D Centre, Faridabad 121007, India.

Abstract

Ruthenium-containing tetraphenylporphyrin (Ru-TPP) molecule was prepared, and the structural elucidation was confirmed using ¹H nuclear magnetic resonance (NMR), CHN, and mass spectral analyses. The incorporation of ruthenium ion into the cavities of the macromolecule was confirmed from the disappearance of the ¹H NMR signal, characteristic of the N-H bond (-2.72 ppm in TPP). The CHN and mass spectral analyses of the ligand and metallomacromolecules are consistent with the theoretically calculated values. The homogeneous Ru-TPP macromolecule is grafted on the surface of aminosilane-, diaminosilane-, and iodosilane-functionalized SBA-15 molecular sieves. The successful grafting of Ru-TPP on functionalized mesoporous molecular sieve materials was evident from low-angle powder X-ray diffraction, ¹³C magic angle spinning NMR, and scanning electron microscopy-energy-dispersive X-ray analyses. The resultant homogeneous and heterogenized Ru-TPP catalysts were used for the utilization of carbon dioxide (CO₂) under moderate reaction conditions. The homogeneous Ru-TPP catalyst showed first-order kinetics with respect to epoxide with the exclusive formation of cyclic carbonate (about 98%) and an activation energy of 16.07 kg/mol, which is much lower than some of the reported catalysts. Ru-TPP grafted on aminosilane- and iodosilane-functionalized materials showed better catalytic activity (above 90% conversion and 83-96% cyclic carbonate selectivity) and reusability for the chosen reaction.