Synthesis of a BC6 polymer via cyclotrimerization of alkynylborane and its application as a heterogeneous Lewis acid catalyst

Lewis acidic boron-containing π-conjugated polymer materials have been demonstrated to be promising for sensing and catalysis; however, the synthetic approaches and the number of installed boron atoms have been limited. Herein, we report the synthesis of a BC6 polymer structure via cyclotrimerization of alkynes. The resulting polymer exhibited superior catalytic activity to small-molecule analogues such as BPh3 and previously reported boron-containing polymers. This enhanced performance is attributed to the high boron content and increased Lewis acidity of BC6, as supported by theoretical and experimental analyses. Owing to its polymeric nature, the catalyst was readily recovered and reused in the catalytic system. These findings demonstrate that building rigid polymer frameworks with a high density of Lewis acidic boron sites is a promising approach to developing recyclable heterogeneous Lewis acid catalysts, and offers a broadly applicable design principle for functional boron-containing polymeric materials.