Amplified Rate Acceleration by Simultaneous Up-Regulation of Multiple Active Sites in an Endo-Functionalized Porous Capsule

Using the hydrolysis of epoxides in water as a model reaction, the effect of multiple active sites on Michaelis–Menten compliant rate accelerations in a porous capsule is demonstrated. The capsule is a water-soluble I h -symmetry Keplerate-type complex of the form, [{MoVI 6O21(H2O)6}12{MoV 2O4(L)}30]42–, in which 12 pentagonal “ligands,” {(MoVI)­MoVI 5O21(H2O)6}6–, are coordinated to 30 dimolybdenum sites, {MoV 2O4L}1+ (L = an endohedrally coordinated η2-bound carboxylate anion), resulting in 20 Mo9O9 pores. When “up-regulated” by removal of ca. one-third of the blocking ligands, L, an equal number of dimolybdenum sites are activated, and the newly freed-up space allows for encapsulation of nearly twice as many substrate guests, leading to a larger effective molarity (amplification), and an increase in the rate acceleration (k cat/k uncat) from 16,000 to an enzyme-like value of 182,800.