Porous crystalline olefin-linked covalent organic frameworks

The\nfirst unsubstituted olefin-linked covalent organic framework,\ntermed COF-701, was made by linking 2,4,6-trimethyl-1,3,5-triazine\n(TMT) and 4,4′-biphenyldicarbaldehyde (BPDA) through Aldol\ncondensation. Formation of the unsubstituted olefin (-CHCH-)\nlinkage upon reticulation is confirmed by Fourier transform infrared\n(FT-IR) spectroscopy and solid-state ¹³C cross-polarization\nmagic angle spinning (CP-MAS) NMR spectroscopy of the framework and\nof its ¹³C-isotope-labeled analogue. COF-701 is found to\nbe porous (1715 m² g^–1) and to retain\nits composition and crystallinity under both strongly acidic and basic\nconditions. The high chemical robustness is attributed to the unsubstituted\nolefin linkages. Immobilization of the strong Lewis acid BF₃·OEt₂ in the pores of the structure yields BF₃⊂COF-701. In the material, the catalytic activity of\nthe guest is retained, as evidenced in a benchmark Diels–Alder\nreaction.