Interpenetrated Metal-Organic Frameworks with ftw Topology and Versatile Functions.

Through an "isoreticular expansion" strategy, a large number of highly porous zirconium-based metal-organic-frameworks (Zr-MOFs) have been achieved using extended organic linkers in the past few years. However, interpenetrated Zr-MOFs with ftw topology have scarcely been reported, mainly owing to the used bulky tetratopic linkers effectively prevent the network interpenetration. Here we report a new family of zirconium and lanthanide (Ln) MOFs with ftw topology, constructed by hexanuclear Zr or Ln (Ln = Eu, Tb, Gd, Dy, Tm, Yb, Nd, Er) clusters and a spirobifluorene-center tetracarboxylate linker. Our studies reveal that the isostructural Zr and Ln MOFs are all doubly interpenetrated with ultrahigh thermal and chemical stability. The observed unusual interpenetration can be attributed to the specific geometry of the spirobifluorene-center tetratopic linker. Gas adsorption studies show that the interpenetrated Zr-MOF is still highly porous and exhibits high performance for CO2 storage, which can be attributed to the strong CO2 binding environment delivered from the reduced pore size. In addition, presented MOFs display strong characteristic luminescence in the UV-vis-NIR region. Moreover, the incorporation of the spiro-center linker into the framework can efficiently produce two-photon-excited photoluminescence with large action cross-section value, which is also benefited from the high packing density of the nonlinear optical chromophore linker in the interpenetrated structure.