Insight into catalyst of tetramethylguanidine decorated palygorskite for CO2 conversion assisted with zinc halides

The clay mineral-based catalyst assisted with zinc halides was explored for cycloaddition of CO 2 , which was fabricated by modifying tetramethylguanidine (TMG) on palygorskite (Pal). More activated sites and oxygen vacancies were generated in Pal particles, and were found to be favorable for loading TMG after thermal/acid treatment. The composite TMG@P-Pal in combination with ZnBr 2 showed excellent catalytic performance, and the conversion reached 99.0% (selectively >99.0%) for coupling gaseous CO 2 with various epoxides . The kinetics indicated that the catalysis followed a reaction order of one, and the apparent activation energy ( E a = 76.93 kJ·mol −1 ) was derived by the Arrhenius equation . The catalytic activity of zinc halides was confirmed to follow the order of ZnBr 2 > ZnCl 2 > ZnI 2 in producing cyclic carbonates . Both TMG molecules and Pal were found to activate CO 2 based on the DFT calculations. This study elucidates the layer-chain structured palygorskite loaded with ZnBr 2 can be a promising material for catalyzing CO 2 cycloaddition with aid of guanidine molecules. • The modified surface of attapulgite was loaded with guanidine molecules. • Remarkable adsorption of CO 2 and catalytic performance were obtained. • The activity of zinc salts was investigated via experiment and calculation. • Both palygorskite and guanidine were vital to conversion of CO 2 .