A facile and green synthesis of cobalt phthalocyanine-conjugated multiwall carbon nanotube by the Ugi reaction: As an efficient CO2 fixation catalyst

Background: In recent years, the concentrations of carbon dioxide (CO2) in the environment have been rising at a disturbing rate, and accordingly, there is a global goal to reduce the Earth's atmospheric CO2 to achieve a balanced climate. Methods: An efficient heterogeneous CO2 fixation catalytic system was designed purposefully based on the conjugation of multiwall carbon nanotube (MWCNT) with tetra-amino cobalt phthalocyanine (Co-PcTA) through an efficient Ugi four-component reaction (Ugi-4CR). The successful manufacture of catalyst was authenticated by various methods such as SEM, EDS, ICP, TGA XRD, and FT-IR. Subsequently, the catalytic performance of the cobalt phthalocyanine-conjugated MWCNT (Co-PcTA/MWCNTs) was investigated in the preparation of cyclic carbonates via the CO2 fixation reaction. Significant Findings: The optimal reaction conditions are 25 mg of generated catalyst, 13 mg tetrabutylammonium bromide (TBAB) as a co-catalyst, 2.5 bar CO2 pressure, at 80 °C, and 1 h. The remarkable benefits of the present catalyst are efficiency, high CO2 absorption capacity, rapid reaction, mild reaction conditions, non-hazardous, reusability, operational simplicity, high yields, and no cobalt leaching in the reaction media. © 2022 Taiwan Institute of Chemical Engineers