From a combination of chiral Mn(salen) struts and the tetratopic ligand tetrakis(4-carboxypheny1)-benzene, a large-pore, noncatenated metal-organic framework (MOF) material, MnSO-MOF, has been synthesized. Following solvent exchange with hydrophobic CHCl3, treatment of MnSO-MOF with aqueous H2O2 allowed for the selective demetalation of Mn(salen) struts at and near the surface of the crystals. The resulting crystals displayed greatly enhanced size-selective catalysis compared to the as-synthesized material. Handling of the mechanically fragile MnSO-MOF crystals was greatly facilitated by activation with supercritical CO2.