Donor–Acceptor-Type Conjugated Porous Organic Polymer for Photocatalytic One-Pot Wittig Olefination of Aldehydes

A novel donor–acceptor-type porous organic polymer (POP) was synthesized using 4,4′,4″,4‴-tetrakis(p-formylphenyl)tetraphenylethylene and 3,3′,5,5′-tetracyanomethyl-2,2′,6,6′-tetramethylbiphenyl as building blocks by the Knoevenagel polycondensation reaction in EtOH, a green solvent. The tetraarylethylene-based POP, namely, TAE-POP, was comprehensively characterized by spectroscopic and microscopic imaging techniques such as FT-IR spectroscopy, solid-state 13C NMR, SEM, TEM, etc. The incorporation of an electron-deficient moiety, i.e., cyanovinylene, and an electron-donating unit, i.e., tetraphenylethylene, into the polymer framework leads to the formation of donor–acceptor (D–A) structural motifs, enhancing the overall performance of the POP as a heterogeneous photocatalyst by facile charge transfer. An exceptional catalytic activity of TAE-POP is demonstrated for the olefination of aldehydes under visible-light irradiation. The catalyst is shown to exhibit remarkable efficiency, affording the olefin products in yields of up to 98% under mild reaction conditions. Mechanistic investigations offer credence to electron transfer as the underpinning pathway in the overall photocatalytic process. The recyclability and remarkable stability of the catalyst, as demonstrated for eight consecutive reaction cycles without a loss of activity, in conjunction with the heterogeneous nature of the reactions, promise a high potential for practical industrial applications.