Two-dimensional (2D) layered double metal cyanides as alternative catalysts for CO/propylene oxide copolymerization

Although zinc-cobalt double metal cyanide (DMC) complex is a popular catalyst for the copolymerization of CO 2 and epoxides, it faces important challenges, such as poor CO 2 uptake, high cyclic carbonate formation, low ability to produce high-molecular-weight polymers, and an induction period. Therefore, the pursuit of alternative DMC complexes that can overcome these limitations has been a recurring research strategy in recent years. In this work, four novel 2D layered tetracyanonickelate complexes (M′[Ni(CN) 4 ]; M′ = Ni 2+ , Co 2+ , Fe 2+ , Mn 2+ ) were prepared, thoroughly characterized, and tested as catalysts for CO 2 and propylene oxide copolymerization. These complexes yielded random polyethercarbonates ( R PEC = 51-94%) with medium-to-low CO 2 content ( F CU = 13.1-42.4 mol%), moderate molecular weight ( M n = 11 000-36 500 g mol −1 ), and broad dispersity ( = 2.5-5.0). The Co-Ni DMC catalyst led to a 100% conversion of PO after 24 h, thus revealing itself as a possible alternative to the classic Zn-Co DMC compound. The catalytic performance of these compounds was compared in detail and their kinetics were assessed by in situ IR spectroscopy. While the Co-Ni DMC complex demonstrated remarkable selectivity, it requires further improvements in terms of activity and CO 2 uptake to surpass its counterpart. Future research efforts should focus on driving these critical aspects. Layered 2D DMC complexes were first catalysts for green copolymerization of CO 2 and PO to produce biodegradable and biocompatible polymers. The Co[Ni(CN) 4 ] complex showed promising potential in this process and was further evaluated.