Enzyme-Mimic Photoinitiated Flow-Polymerization with High Stereoselectivity under Mild Conditions

Enzymatic reactions can achieve efficient flow-polymerization with specificity and high stereoselectivity. However, current enzyme-mimic polymerization systems cannot achieve high stereoregularity in flow reactions under mild conditions. This inefficient chain control may be due to the absence of a specific catalyst structure for the target monomer. This study reports a model of enzyme-mimic catalytic material for the polymerization of a specific monomer. In particular, the specific enzyme-mimic photoinitiated flow-polymerization of benzyl acrylate was realized at 22 °C using zinc porphyrin metal-organic framework (Zn-PMOF) membranes with one-dimensional nanochannels, achieving the efficient synthesis of highly heterotactic polymers. Under visible light irradiation, the zinc porphyrin core on the membrane surface could initiate polymerization, while copper porphyrin MOF with similar structures could not. The specific channel structure of the Zn-PMOF membrane provided space for stereochemical control. Control experiments, density functional theory simulations, and spectroscopic characterizations show that the combination of size effect and channel-monomer interactions realized higher monomer conversion and polymer stereoregularity in the flow reaction. Furthermore, the crystallinity, shear stress, and ionic conductivity of enzyme-mimic polymers were considerably better than those of bulk polymerization products. Thus, this study provides a method for enzyme-mimic polymerization with high stereoselectivity under mild conditions.