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

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 45 min. 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 (1.4 mmol at 273 K and 1.0 mmol at 298 K). We have also analyzed the thermodynamics of CO₂ affinity on Zr-TPA-MOF thoroughly. So, this property has been explored further, where Zr-TPA-MOF is used 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.