Fabrication of [D][Br]@sUiO-66-NH₂ as a Catalyst for Solvent- and Cocatalyst-Free CO₂ Cycloaddition with Epoxides

Conventional bromide cocatalysts such as tetrabutylammonium bromide (TBAB) are effective for the cycloaddition of CO₂ with epoxides, but their industrial application is limited by difficult separation and poor recyclability. Herein, an ionic metal-organic framework (IMOF) catalyst, [D][Br]@sUiO-66-NH₂, was prepared by immobilizing 1-H-1,4-diazabicyclo[2.2.2]octane bromide ([D][Br]) on sUiO-66-NH₂ through postsynthetic modification. XRD, FT-IR, XPS, SEM, N₂ physisorption, and TG analyses (TGA) confirmed the successful incorporation of [D][Br] while preserving the framework structure and porosity of the support. Under solvent- and cocatalyst-free conditions, the catalyst achieved quantitative conversion of styrene oxide (SO) with 80.55% selectivity to styrene carbonate (SC) at 110 °C and 1.0 MPa CO₂ after 12 h using 6.0 wt % catalyst. The catalyst also exhibited good reusability, with the GC yield of SC decreasing only slightly from 80.55% to 79.38% after 8 cycles. These results demonstrate that MOF-based immobilization of DABCO-derived bromide species is an effective strategy for developing recyclable heterogeneous catalysts for CO₂ cycloaddition.