Direct B–H Bond Activation Polymerization of Boron Clusters

Selective and efficient functionalization of boron clusters, particularly carboranes, at the boron vertices poses significant synthetic challenges due to the inherent inertness of B-H bonds and pronounced regioselectivity issues. While recent advances in B-H bond functionalization have attracted growing interest in boron cluster diversification in small molecular systems, the construction of boron cluster-based polymers through direct B-H bond activation polymerization remains unexplored. Here, we report an unprecedented Pd-catalyzed B-H bond activation polymerization of <i>nido</i>-carboranes with internal diynes, affording boron-site-substituted polymers featuring high molecular weights (<i>M</i>_w up to 103.8 kg/mol) and excellent yields (up to 99%). Owing to the dense incorporation of <i>nido</i>-carborane units along the backbone, the resulting polymers demonstrate excellent degradability under mild conditions. Using this versatile polymerization strategy, we constructed aggregation-induced emission (AIE)-active polymers for bioimaging and boron delivery agents, showing evident neutron capture therapy efficacy against tumor cells. This work establishes a general and facile route to construct degradable, multifunctional boron cluster-based polymers, demonstrating their potential applications in materials and biomedicine.