Network Flexibility: Control of Gate Opening in an Isostructural Series of Ag-MOFs by Linker Substitution

An isostructural series of 15 structurally flexible microporous silver metal–organic frameworks (MOFs) is presented. The compounds with a dinuclear silver core as secondary building unit (Ag₂N₄) can be obtained under solvothermal conditions from substituted triazolyl benzoate linkers and AgNO₃ or Ag₂SO₄; they exhibit 2-fold network interpenetration with <b>lvt</b> topology. Besides the crystal structures, the calculated pore size distributions of the microporous MOFs are reported. Simultaneous thermal analyses confirm the stability of the compounds up to 250 °C. Interconnected pores result in a three-dimensional pore structure. Although the porosity of the novel coordination polymers is in the range of only 20–36%, this series can be regarded as a model system for investigation of network flexibility, since the pore diameters and volumes can be gradually adjusted by the substituents of the 3-(1,2,4-triazol-4-yl)-5-benzamidobenzoates. The pore volumes of selected materials are experimentally determined by nitrogen adsorption at 77 K and carbon dioxide adsorption at room temperature. On the basis of the flexible behavior of the linkers a reversible framework transformation of the 2-fold interpenetrated network is observed. The resulting adsorption isotherms with one or two hysteresis loops are interpreted by a gate-opening process. Due to external stimuli, namely, the adsorptive pressure, the materials undergo a phase transition confirming the structural flexibility of the porous coordination polymer

Multifunctional Phosphate-Based Inorganic–Organic Hybrid Nanoparticles

Phosphate-based inorganic–organic hybrid nanoparticles (IOH-NPs) with the general composition [<i>M</i>]²⁺[<i>R</i>_{<i>function</i>}(O)­PO₃]^2– (<i>M</i> = ZrO, Mg₂O; <i>R</i> = functional organic group) show multipurpose and multifunctional properties. If [<i>R</i>_{<i>function</i>}(O)­PO₃]^2– is a fluorescent dye anion ([<i>R</i>_<i>dye</i>OPO₃]^2–), the IOH-NPs show blue, green, red, and near-infrared fluorescence. This is shown for [ZrO]²⁺[PUP]^2–, [ZrO]²⁺[MFP]^2–, [ZrO]²⁺[RRP]^2–, and [ZrO]²⁺[DUT]^2– (PUP = phenylumbelliferon phosphate, MFP = methylfluorescein phosphate, RRP = resorufin phosphate, DUT = Dyomics-647 uridine triphosphate). With pharmaceutical agents as functional anions ([<i>R</i>_<i>drug</i>OPO₃]^2–), drug transport and release of anti-inflammatory ([ZrO]²⁺[BMP]^2–) and antitumor agents ([ZrO]²⁺[FdUMP]^2–) with an up to 80% load of active drug is possible (BMP = betamethason phosphate, FdUMP = 5′-fluoro-2′-deoxyuridine 5′-monophosphate). A combination of fluorescent dye and drug anions is possible as well and shown for [ZrO]²⁺[BMP]^2–_0.996[DUT]^2–_0.004. Merging of functional anions, in general, results in [ZrO]²⁺([<i>R</i>_<i>drug</i>OPO₃]_1–<i>x</i>[<i>R</i>_<i>dye</i>OPO₃]_<i>x</i>)^2– nanoparticles and is highly relevant for theranostics. Amine-based functional anions in [MgO]²⁺[<i>R</i>_<i>amine</i>PO₃]^2– IOH-NPs, finally, show CO₂ sorption (up to 180 mg g^–1) and can be used for CO₂/N₂ separation (selectivity up to α = 23). This includes aminomethyl phosphonate [AMP]^2–, 1-aminoethyl phosphonate [1AEP]^2–, 2-aminoethyl phosphonate [2AEP]^2–, aminopropyl phosphonate [APP]^2–, and aminobutyl phosphonate [ABP]^2–. All [<i>M</i>]²⁺[<i>R</i>_{<i>function</i>}(O)­PO₃]^2– IOH-NPs are prepared via noncomplex synthesis in water, which facilitates practical handling and which is optimal for biomedical application. In sum, all IOH-NPs have very similar chemical compositions but can address a variety of different functions, including fluorescence, drug delivery, and CO₂ sorption

An Isomorphous Series of Cubic, Copper-Based Triazolyl Isophthalate MOFs: Linker Substitution and Adsorption Properties

An isomorphous series of 10 microporous copper-based metal–organic frameworks (MOFs) with the general formulas _∞³[{Cu₃(μ₃-OH)­(X)}₄{Cu₂(H₂O)₂}₃(H-R-trz-ia)₁₂] (R = H, CH₃, Ph; X^2– = SO₄^2–, SeO₄^2–, 2 NO₃^2– (<b>1</b>–<b>8</b>)) and _∞³[{Cu₃(μ₃-OH)­(X)}₈{Cu₂(H₂O)₂}₆(H-3py-trz-ia)₂₄Cu₆]­X₃ (R = <i>3</i>py; X^2– = SO₄^2–, SeO₄^2– (<b>9</b>, <b>10</b>)) is presented together with the closely related compounds _∞³[Cu₆(μ₄-O)­(μ₃-OH)₂(H-Metrz-ia)₄]­[Cu­(H₂O)₆]­(NO₃)₂·10H₂O (<b>11</b>) and _∞³[Cu₂(H-3py-trz-ia)₂(H₂O)₃] (<b>12</b>^<b>Cu</b>), which are obtained under similar reaction conditions. The porosity of the series of cubic MOFs with <b>twf-d</b> topology reaches up to 66%. While the diameters of the spherical pores remain unaffected, adsorption measurements show that the pore volume can be fine-tuned by the substituents of the triazolyl isophthalate ligand and choice of the respective copper salt, that is, copper sulfate, selenate, or nitrate