Shape-Controlled synthesis of conjugated microporous polymer nanotubes and their implementation in continuous flow polymerization

Flow reactors have materialized as a reliable and sustainable approach toward polymer production and processing to promote efficient and uniform irradiation pathways. However, the disadvantages of existing homogeneous photocatalysts including noxiousness, restricted photocatalytic activity and stability, and difficult separation and purification, still pose a great challenge to the advancement of this technique. Herein, conjugated microporous polymer nanotubes (hPorBDP NTs) were fabricated through Sonogashira-Hagihara cross-coupling polycondensation with silica nanorods as sacrificial templates, followed by etching of the inner cores. The hPorBDP NTs with a hollow nanostructure and a highly porous texture were demonstrated to facilitate the separation procedure and provide more accessible active sites for photocatalytic reactions. The hPorBDP NTs were employed as heterogeneous catalysts to activate photoinduced electron/energy transfer-reversible additionfragmentation chain transfer (PET-RAFT) polymerization in batch and in continuous flow system. Screening of the initial monomer concentrations and pump flow rates, high monomer conversions (alpha > 80%) and narrow dispersities (D < 1.15) were achieved in continuous flow system for upscaled production of polymers. Separation and reutilization of the catalyst-bound NTs were realized through facile centrifugation, which resulted in negligible leaching and maintenance of catalytic performance over multiple polymerization cycles. As such, the development of photosynthesis system using hPorBDP NTs as heterogeneous photocatalysts should broaden the application scope of these fascinating catalysts while benefiting synthetic upscaling by continuous flow polymerization.

Automated summary

Conjugated microporous polymer nanotubes (hPorBDP NTs) were fabricated as heterogeneous catalysts for photoinduced electron/energy transfer-reversible addition-fragmentation chain transfer (PET-RAFT) polymerization in batch and continuous flow systems. The hPorBDP NTs exhibited a hollow nanostructure and a highly porous texture, enabling efficient separation and more accessible active sites for photocatalytic reactions. The catalyst-bound NTs could be easily recovered through centrifugation with negligible leaching and maintained catalytic performance over multiple polymerization cycles.