Photocatalytically Active Mechanically Interlocked Carbon Nanotubes

This work presents the heterogenization of phenothiazine-based photocatalysts onto carbon nanotubes (CNTs) through mechanical interlocking. Two different photocatalysts featuring a phenothiazine core were synthesized. Both derivatives were successfully clipped onto single-walled carbon nanotubes (SWNTs) of different diameters by means of ring-closing metathesis. Comprehensive characterization of the resulting mechanically interlocked carbon nanotubes (MINTs) bearing the photocatalysts, using spectroscopic, microscopic, and computational techniques, confirms the effectiveness of the procedure, achieving a functionalization degree of 10%-14% with photoactive materials. These photocatalyst-MINT hybrids were subsequently evaluated in the photocatalytic borylation of aryl halides. Both MINT materials exhibited similar or improved performance compared to their homogeneous counterparts, while also demonstrating enhanced substrate tolerance, recyclability, and robustness. Furthermore, the mechanism of the photocatalytic reaction mediated by the MINT materials was investigated through both experimental and computational studies. The results highlight the importance of electronic communication between the nanotube and the molecular photocatalyst for achieving the observed catalytic behavior.