A Nanoporous Ag−Fe Mixed-Metal−Organic Framework Exhibiting Single-Crystal-to-Single-Crystal Transformations upon Guest Exchange

The reaction of solutions of Fe(Pyac)3 [PyacH = 3-(4-pyridyl)-2,4-pentanedione] and AgNO3 produces two types of porous mixed-metal−organic frameworks (M′MOFs). With lower AgNO3 concentrations, the product (M′MOF1) has a 2D honeycomb structure with Ag:Fe = 1:1 and pores of ca. 12 × 16 Å. When a higher concentration of AgNO3 is employed, however, the product (M′MOF2) has Ag:Fe = 3:2 and a porous 1D ladder structure. A variety of nonpolar solvents serve as guests in M′MOF2: with 1,2-C6H4Cl2, [AgNO3]3[Fe(Pyac)3]2(1,2-C6H4Cl2)5.5 (M′MOF2a); with C6H5Br, [AgNO3]3[Fe(Pyac)3]2(C6H5Br)6 (M′MOF2b). M′MOFs 2a and 2b can be interconverted by treatment with the appropriate solvent, in single-crystal-to-single-crystal transformations.