[2 + 2] light-driven cycloaddition synthesis of an organic polymer and photocatalytic activity enhancement via monomer truncation

Abstract

The synthesis of covalent organic polymers usually relies on polar reactions for the establishment of linkages among the constituent monomers. Herein, the photochemical [2 + 2] olefin cycloaddition reaction is employed as a polymerization tool to yield organic polymers in which the connectivity is based on cyclobutane moieties, as demonstrated by the characterization techniques. The functionalization of the polymer is carried out by means of the monomer truncation strategy with monotopic olefins decorated with different motifs, including the organic photocatalyst 10-phenyl-phenothiazine (PTH), achieving its connection with a homogeneous 10% functionalization degree. All materials are active photocatalysts in the light-driven oxidative coupling of benzyl amines to the corresponding imines, but the functionalized polymer bearing a photoactive moiety shows an enhancement of the catalytic performance. Indeed, the functionalized-PTH polymer exhibits higher activity (75% yield vs. ∼40% yield) and a stable recyclable character without leaching compared to the non-truncated sample.