Zinc phthalocyanine-based porous organic polymer for cycloaddition reaction of carbon dioxide and epoxides
Zinc phthalocyanine-based porous organic polymer(denoted as ZnPc-POP)was prepared from Schiff-base condensation reaction of zinc tetraminophthalocyanine and 1,3,5-benzenetricarboxaldehyde under solvothermal conditions,and characterized by FTIR,13CNMR,XPS,TEM and N2 adsorption-desorption.The catalytic performance,recycling ability and substrate applicability of ZnPc-POP were evaluated via cycloaddition reaction of epichlorohydrin(ECH)and CO2 as model and tetrabutylammonium bromide(TBAB)as cocatalyst,and the catalytic mechanism was explored.The results showed that ZnPc-POP exhibited a structure with abundant mesopores(pore volume was about 0.64 cm3/g,average pore size was about 20 nm)and large specific surface area(171.6 m2/g).At 100℃and 1.0 MPa CO2,the selectivity of ECH to produce cyclic carbonate was>99%,the yield reached 96%,and the turnover frequency(TOF)was up to 533.3 h-1.ZnPc-POP showed no significant decrease in the catalytic activity after being recycled for 5 times.The selectivity of the cycloaddition reaction catalyzed by ZnPc-POP with different epoxides as substrates was greater than or equal to 96%.The ternary oxygen atom in the epoxide was activated effectively by coordination with the Lewis acidic zinc center of ZnPc-POP,and the bromine ion in the co-catalyst TBAB promoted the ring-opening of the epoxide through nucleophilic attack.This double activation of epoxide ring-opening was the rate-controlling step of CO2 cycloaddition reaction.