Nanosheet‐Assembled Zirconium‐Porphyrin Frameworks Enabling Surface‐Confined, Initiator‐Free Photosynthesis of Ultrahigh Molecular Weight Polymers

Abstract

AbstractMetal–organic frameworks with well‐organized low‐dimensional architectures provide significant thermodynamic and/or kinetic benefits for diverse applications. We present here the controlled synthesis of a novel class of hierarchical zirconium‐porphyrin frameworks (ZrPHPs) with nanosheet‐assembled hexagonal prism morphology. The crystal growth behaviors and structural evolution of ZrPHPs in an additive‐modulated solvothermal synthesis are examined, showing an “assembly‐hydrolysis‐reassembly” mechanism towards the formation of 2D nanosheets with ordered arrangement. Because of the highly‐accessible active sites harvesting broadband photons, ZrPHPs serve as adaptable photocatalysts to regulate macromolecular synthesis under full‐range visible light and natural sunlight. An initiator‐free, oxygen‐tolerant photopolymerization system is established, following a distinctive mechanism involving direct photo‐induced electron transfer to dormant species and hole‐mediated reversible deactivation. Specifically, ZrPHPs provide a surface‐confined effect towards the propagating chains which inhibits their recombination termination, enabling the highly‐efficient synthesis of ultrahigh molecular weight polymers (Mn >1,500,000) with relatively low dispersity (Đ≈1.5).