A Supported Catalyst that Enables the Synthesis of Colorless CO2‐Polyols with Ultra‐Low Molecular Weight
A strategy for constructing a supported catalyst featuring immobilization-enhanced proton tolerance for the synthesis of colorless ULMW CO2-polyols is proposed. The key design feature lies in the loading of aluminum aminoporphyrins on swellable Merrifield resin to afford the multiple cooperativity of porphyrins in the supported catalysts.
Ultra-low molecular weight (ULMW) CO2-polyols with well-defined hydroxyl end groups represent useful soft segments for the preparation of high-performance polyurethane foams. However, owing to the poor proton tolerance of catalysts towards CO2/epoxide telomerization, it remains challenging to synthesize ULMW yet colorless CO2-polyols. Herein, we propose an immobilization strategy of constructing supported catalysts by chemical anchoring of aluminum porphyrin on Merrifield resin. The resulting supported catalyst displays both extremely high proton tolerance (≈8000 times the equivalents of metal centers) and independence of cocatalyst, affording CO2-polyols with ULMW (580 g mol−1) and high polymer selectivity (>99 %). Moreover, the ULMW CO2-polyols with various architectures (tri-, quadra-, and hexa-arm) can be obtained, suggesting the wide proton universality of supported catalysts. Notably, benefiting from the heterogeneous nature of the supported catalyst, colorless products can be facilely achieved by simple filtration. The present strategy provides a platform for the synthesis of colorless ULMW polyols derived from not only CO2/epoxides, but also lactone, anhydrides etc. or their combinations.Zum Volltext
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