Boosting Photocatalytic Activities for Organic Transformations through Merging Photocatalyst and Transition-Metal Catalyst in Flexible Polymers

The merger of photocatalysis and transition-metal catalysis is of particular interest to develop useful and challenging synthetic methodologies. The catalytic activities of conventional dual-catalytic systems, however, are limited by the low synergistic efficiency between discrete catalytic centers due to their long average distance in solution. Herein we carefully decorated Ir(III) photosensitizers and Ni(II) transition-metal catalyst into flexible polymers to afford two polymer-supported dual catalysts (P1-Ni and P2-Ni). These polyelectrolyte-type metallopolymers assembled into spherical polymer particles in some polar solvents. Their unique molecular and assembled structure contributed to shortening the distance between catalytic centers and increasing the local catalysts' concentration within the catalyst, thereby greatly facilitating their electron, energy, and organic radical transfers during the catalytic cycles. The enhanced energy interaction and matched redox potential between two catalytic centers within the polymer were confirmed by steady- and transient-state luminescent spectra and cyclic voltammetry. These features enable them in catalyzing challenging organic transformations that involve efficiently incorporated photocatalytic and transition-metal catalytic cycles. We demonstrated that these two catalysts were highly effective in catalyzing C-S cross-coupling, C-O functionalized, C-N cross-coupling, and C-C cross-coupling reactions with broad substrate scopes and low catalyst loadings with turnover numbers of similar to 3100, similar to 1500, similar to 1400, and similar to 500, respectively. This work provides a general methodology to merge photosensitizer and transition-metal catalyst in a flexible polymer for significantly boosting the catalytic activity.