A crystalline and stable microporous framework based on the dative B←N bonds

Summary

The concept of making use of dative boron–nitrogen (B←N) bonds for the construction of microporous crystalline organic framework (BNF) materials has been proposed but not fulfilled, and they have not been fully explored for their diverse functions because of the difficulty to stabilize their pore structures under thermal/vacuum activation. In this study, we report the first such stable crystalline framework in which the single-crystal X-ray structures of the as-synthesized BNF-1, activated BNF-1a, and C₂H₂-loaded BNF-1a have been clearly characterized. Here, the 2D framework sheets of BNF-1 were interlocked with one another, generating the stable and crystalline framework with a Brunauer-Emmett-Teller (BET) surface area of 255 m²/g. Also, the material takes up more C₂H₂ than CO₂ molecules, and breakthrough experiments demonstrate its separation performance for C₂H₂/CO₂ mixtures. The molecular recognition mechanism of this BNF-1 for the preferential binding of C₂H₂ molecules over CO₂ has been comprehensively studied by both single-crystal X-ray diffraction and molecular modeling.