Functionalization of Poplar cotton via azido-Ugi reaction: as a green biocatalytic system for the chemical fixation of CO2

Cellulose is the most common renewable polysaccharide on the planet and one of the most important sources of green support to generate catalysts. According to that, the fluffy cotton-like seed of the black poplar tree (Populus nigra subsp. betulifolia) was first used as a source of natural cellulose to construct the green, efficient, and recyclable catalyst for the synthesis of cyclic carbonate from carbon dioxide (CO2). Black poplar cotton (BPC) was efficiently oxidized to dialdehyde cellulose (DAC) using periodate and participated in the azido-Ugi four-component reaction (AU-4CRs) of sulfonamide, isocyanide, and sodium azide to produce tetrazole immobilized on cellulose (DAC-AU) as a ligand. Afterward, the heterogeneous biocatalyst (Cu(II)@DAC-AU) was prepared, and the catalytic activity of the biocatalyst was investigated in the cycloaddition reaction of epoxides and CO2. This study has proven to have the most optimal catalytic activity, including excellent performance up to 99% after 4 h under CO2 pressure of 1 bar. The hydroxy and tetrazole functional groups on the surface of cellulose can absorb CO2 effectively and improve its catalytic activity. This work highlights the applications of the biocatalyst in a cycloaddition reaction and provides an efficient remedy for the industrial conversion of CO2. [GRAPHICS]