2D Graphene Oxide Membrane Nanoreactors for Rapid Directional Flow Ring-Opening Reactions with Dominant Same-Configuration Products.

Nanoconfinement within enzymes can increase reaction rate and improve selectivity under mild conditions. However, it remains a great challenge to achieve chemical reactions imitating enzymes with directional molecular motion, short reaction time, ≈100% conversion, and chiral conversion in artificial nanoconfined systems. Here, directional flow ring-opening reactions of styrene oxide and alcohols are demonstrated with ≈100% conversion in <120 s at 22 °C using graphene oxide membrane nanoreactors. Dominant products have the same configuration as chiral styrene oxide in confined reactions, which is dramatically opposed to bulk reactions. The unique chiral conversion mechanism is caused by spatial confinement, limiting the inversion of benzylic chiral carbon. Moreover, the enantiomeric excess of same-configuration products increased with higher alkyl charge in confined reactions. This work provides a new route to achieve rapid flow ring-opening reactions with specific chiral conversion within 2D nanoconfined channels, and insights into the impact of nanoconfinement on ring-opening reaction mechanisms.

Efficient Flow Synthesis of Aspirin within 2D Sub-Nanoconfined Laminar Annealed Graphene Oxide Membranes.

The aim of this work is to develop an environmentally friendly, safe, and simple route for realizing efficient preparation of aspirin. Here, inspired by enzyme synthesis in vivo, the aspirin synthesis has been realized by sub-nanoconfined esterification with directional flow and ≈100% conversion in an unprecedented reaction time of <6.36 s at 23 °C. Such flow esterification reaction is catalyzed by thermally transformed graphene oxide (GO) membranes with tailored physicochemical properties, which can be obtained simply through a mild annealing method. A possible mechanism is revealed by density functional theory calculation, indicating that the synergistic effect of spatial confinement and surface electronic structure can significantly improve the catalytic performance. By restricting reactants within 2D sub-nano space created by GO-based laminar flow-reactors, the present strategy provides a new route to achieve rapid flow synthesis of aspirin with nearly complete conversion.