Luminescent metal organic frameworks for sensing and gas adsorption studies

Two three-dimensional metal organic frameworks (MOFs) with a 5,5 ',5 ''-(2,4,6-trimethyl-1,3,5-phenylene)tris(methylene)tris(azanediyl)triisophthalic acid (H6L) ligand, viz., {[Zn-4(L)(1/3)(H2O)(4)](6+)[S]}(n) (LZn) and {[NaCd2(L)(DMF)(3)](-)center dot(Me2NH2+)(3DMF)}(n) (LCd), where the S in LZn denotes a squeezed anion and solvent molecules and DMF denotes dimethylformamide, were synthesized under solvothermal conditions. LZn is a porous compound that contains paddle wheel binuclear [Zn-2(COO)(4) and Zn-2(COO)(3)] secondary building units (SBUs), while LCd is an intrapenetrating MOF with Cd2Na trinuclear SBUs. The sensing results showed that both MOFs act as selective sensors towards nitrophenolic explosives, i.e., nitrophenol (NP), dinitrophenol (DNP), and trinitrophenol (TNP). Furthermore, LCd exhibited behavior that is typical of an ultramicroporous material and selectively adsorbed CO2, while N-2 molecules were adsorbed only on its surface. By contrast, LZn showed selectivity towards N-2 molecules at 77 K.