Anion-Mediated Allosteric Catalysis of [2+2] Photocycloaddition Based on a Flexible Metallo-Amine Cage for High Diastereoselectivity

Anions can exert a notable influence on the solubility and folding of protein structures, consequently altering their activity and stability due to the well-known Hofmeister effect. Herein, we report a protein-like allosteric metal-organic cage (MOC-68) with the solubility and conformation regulated through anion exchange, leading to conversion between the relaxed state (R-state) and the tensed state (T-state) to show distinct host-guest interactions. This conformational change enables allosteric catalysis of intermolecular [2 + 2] photocycloaddition of acyclic olefins with greatly enhanced yield and diastereoselectivity. Kinetic experiments reveal that the T-state of MOC-68 is superior in catalytic performance for the steric and thermodynamic unfavored syn-HH product, displaying a threefold rate enhancement over the R-state and totally a sevenfold increase owing to the reaction acceleration contributed by an enzymatic cage effect. Notably, this allosteric cage exhibits exceptional stability and recyclability, maintaining consistent catalytic efficiency and selectivity over five cycles. This work highlights the potential of structural allostery in flexible cages to enhance the substrate-binding ability and catalytic selectivity, providing a way to advance enzyme-mimicking cage catalysis to regulatable and efficient allosteric catalysis.