•Functionalized [H(OCH2CH2)nbim][Co(CO)4)] ILs are synthesized successfully.•Thermoregulated phase-separable catalysis (TPSC) system has been established.•The TPSC system exhibits good recycling efficiency in hydroesterification of 4-isobutylstyrene.The synthesis and catalytic performance of stable, efficient, and recyclable multi-functionalized ionic liquid catalysts are reported for the first time. Through an optimized synthetic strategy, a series of polyether-substituted imidazolium cobalt tetracarbonyl salts, [H(OCH2CH2)nbim] [Co(CO)4)] (n = 8, 15, and 22, bim = butylimidazolium), and their intermediates, were successfully synthesized and characterized by IR, UV–vis, 1H NMR, 13C NMR, and TGA. The stability, solubility, and critical solution temperature of the ionic liquids were also determined. A thermoregulated phase-separation catalysis system for the hydroesterification of olefins has been established based on the above multi-functionalized ionic liquid catalyst. The results show that this catalysis system has a high recycling efficiency, and provides a potential method for an environmentally benign carbonylation process.Polyether-substituted imidazolium ionic liquids, representing an affirmative case of stabilizing the highly air sensitive cobalt tetracarbonyl anion, have been successfully synthesized and used in hydroesterification of 4-isobutylstyrene by thermoregulated phase-separable catalysis (TPSC) system. The TPSC system exhibits good recycling efficiency and provides a potential route for an environmentally benign carbonylation reaction.

In this paper, functional ionic liquid 1-butyl-3-methylimidazolium cobalt tetracarbonyl [Bmim][Co(CO)4] is prepared in a metathesis reaction between [Bmim]Cl and KCo(CO)4. The structure of [Bmim]+ is illustrated by 1H NMR, while [Co(CO)4]− is confirmed by IR(νCO) spectrum. Methyl 3-hydroxypropionate(3-HPM), an intermediate to 1,3-propanediol (1,3-PDO), can be prepared in high yield by hydroesterification of ethylene oxide in the presence of a [Bmim][Co(CO)4] catalyst. Under a pressure of 3.7 MPa and at a temperature of 75 °C, the yield of 3-HPM can reach 90.8% in 10 h. Even after the catalyst is recycled three times, a yield of more than 80% can be obtained. A possible reaction mechanism has also been proposed.