On-Demand Transformation of Carbon Dioxide into Polymers Enabled by a Comb-Shaped Metallic Oligomer Catalyst
Han Cao, Ruoyu Zhang, Zhenzhen Zhou, Shunjie Liu, Youhua Tao, Fosong Wang, Xianhong Wang
Abstract
In addition to harsh conditions, CO2 is an excess in most chemical transformations due to its sluggish reactivity. Herein, we realize the on-demand transformation of CO2 in the synthesis of poly(ether carbonate) polyols through a comb-shaped metallic oligomer catalyst, displaying quantitative reaction and product specificity. In contrast to conventional single-site catalysts that suffer from direct depolymerization long before quantitative CO2 conversion, the metallic oligomer catalyst anchoring multiple aluminum porphyrin complexes at the side chain maintains excellent polyol selectivity (>99%), exhibits high polymerization rate (turnover number of 50,000), and exquisitely places all CO2 monomers in the middle of the polyol backbone with oligoetherol end groups. The composition of polyol exactly corresponds to initial CO2 feed ratios of 0.07–0.39. Further studies on the kinetic rate law and activation parameters of key intermediates decipher the multimetallic synergistic catalysis. Hence, this work offers a fresh view of CO2 as an indeed countable monomer rather than ambiguous pressure as normally considered.