Tandem cooperative catalysis over a Zr-MOF for the synthesis of hydroxyurethanes under solvent-free conditions

Abstract

Carbon sequestration via CO2 fixation into value added chemicals is of great importance for the sustainable future of the world. Hydroxyurethane derivatives are very demanding chemical intermediate for the polymer and adhesive industries, which can be synthesized by a tandem sustainable route involving the fixing CO2 on epoxides to cyclic carbonates followed by ring opening through aminolysis. In this work, we have synthesized a crystalline tritopic Zr-based metal-organic framework (MOF) having secondary building unit (SBU) as [Zr6(µ3-O)4(µ3-OH)4(OH)6(TPA-COOH)2] (TPA = triphenylamine), which we coined as Zr-TPA-MOF. This MOF was prepared through a sustainable microwave assisted synthesis route within 45min. at 120 °C. Zr-TPA-MOF exhibited plate like morphology and possesses a good specific surface area of 312 m2g-1. Zr-TPA-MOF material displayed good reversible CO2 uptakes at different temperatures (1.4mmol at 273K and 1.0mmol at 298K). We have also analyzed the thermodynamics of CO2 affinity of Zr-TPA-MOF thoroughly. So, this property has been explored further by using this Zr-TPA-MOF as a heterogeneous catalyst for the CO2 fixation reaction to form hydroxyurethanes over different epoxides via tandem aminolysis. Here, we have enlightened a broader context of CO2 fixation using nontoxic, cost effective Zr-MOF as a promising catalyst in isocyanate-free synthesis of hydroxyurethane derivatives.