Synthesis, Structures and Photoluminescence Properties of a Series of Alkaline Earth Metal-Based Coordination Networks Synthesized Using Thiophene-Based Linkers

Three new 3-D coordination networks were synthesized using alkaline-earth metal centers, calcium, and strontium, with 2,5-thiophenedicarboxylate (TDC) as the organic linker. [Ca₂(TDC-2H)₂(DMF)₂]_<i>n</i> [<b>1</b>, space group <i>P</i>2₁/<i>n</i>, <i>a</i> = 10.0704(3) Å, <i>b</i> = 14.2521(3) Å, <i>c</i> = 17.5644(6) Å, β = 94.281(2)°] is composed of tetrameric calcium polyhedral clusters, which are connected by the organic linkers. Coordinated DMF molecules are present within the 1-D channel along the [010] direction. [Ca­(TDC-2H)]_<i>n</i> [<b>2</b>, space group <i>Pbcm</i>, <i>a</i> = 5.3331(5) Å, <i>b</i> = 6.8981(4) Å, <i>c</i> = 18.141(2) Å] consists of chains of edge-sharing calcium octahedra, connected by organic linkers, to form a dense network. [Sr­(TDC-2H)­(DMF)]_<i>n</i> [<b>3</b>, space group <i>P</i>2₁/<i>n</i>, <i>a</i> = 5.9795(3) Å, <i>b</i> = 17.058(1) Å, <i>c</i> = 11.3592(6) Å, β = 91.257(1)°] forms a structural topology almost identical to compound <b>1</b> except that the chains are built by combinations of edge- and face-sharing polyhedra. Compounds <b>1</b> and <b>3</b> were synthesized using DMF as solvent, whereas compound <b>2</b> crystallizes using ethanol. Photoluminescence studies reveal that the topologies of the networks and the presence of the coordinated solvent molecules control the luminescence properties of the compounds

Synthesis, Structures and Photoluminescence Properties of a Series of Alkaline Earth Metal-Based Coordination Networks Synthesized Using Thiophene-Based Linkers

Three new 3-D coordination networks were synthesized using alkaline-earth metal centers, calcium, and strontium, with 2,5-thiophenedicarboxylate (TDC) as the organic linker. [Ca₂(TDC-2H)₂(DMF)₂]_<i>n</i> [<b>1</b>, space group <i>P</i>2₁/<i>n</i>, <i>a</i> = 10.0704(3) Å, <i>b</i> = 14.2521(3) Å, <i>c</i> = 17.5644(6) Å, β = 94.281(2)°] is composed of tetrameric calcium polyhedral clusters, which are connected by the organic linkers. Coordinated DMF molecules are present within the 1-D channel along the [010] direction. [Ca­(TDC-2H)]_<i>n</i> [<b>2</b>, space group <i>Pbcm</i>, <i>a</i> = 5.3331(5) Å, <i>b</i> = 6.8981(4) Å, <i>c</i> = 18.141(2) Å] consists of chains of edge-sharing calcium octahedra, connected by organic linkers, to form a dense network. [Sr­(TDC-2H)­(DMF)]_<i>n</i> [<b>3</b>, space group <i>P</i>2₁/<i>n</i>, <i>a</i> = 5.9795(3) Å, <i>b</i> = 17.058(1) Å, <i>c</i> = 11.3592(6) Å, β = 91.257(1)°] forms a structural topology almost identical to compound <b>1</b> except that the chains are built by combinations of edge- and face-sharing polyhedra. Compounds <b>1</b> and <b>3</b> were synthesized using DMF as solvent, whereas compound <b>2</b> crystallizes using ethanol. Photoluminescence studies reveal that the topologies of the networks and the presence of the coordinated solvent molecules control the luminescence properties of the compounds

Simultaneous <i>in Situ</i> X‑ray Diffraction and Calorimetric Studies as a Tool To Evaluate Gas Adsorption in Microporous Materials

Combined application of <i>in situ</i> X-ray diffraction (XRD) and differential scanning calorimetry (DSC) is a novel technique for rapidly evaluating the suitability of microporous materials for postcombustion CO₂ capture. Further, while many microporous materials show promise for CO₂ capture, most are not evaluated in the presence of water vapor, a major component of postcombustion flue gas. As a demonstration of the versatility of XRD-DSC techniques, representatives of the classes of materials typically proposed for CO₂ capture, zeolites, and metal–organic frameworks (MOFs) were studied: zeolite NaX, Ni-MOF-74 [Ni₂(dobdc); dobdc = 2,5-dihydroxy­terephthalate], ZIF-7 [ZIF: zeolitic imidazole framework, Zn­(phim)₂; phim: benzimidazole], and SBMOF-1 [Ca­(sdb); sdb: 4,4′-sulfonyl­dibenzoate]. Although NaX and Ni-MOF-74 show very high affinity toward CO₂ under idealized dry conditions, they are also very sensitive to the presence of water vapor and experience significant performance loss above 25% relative humidity (RH) at room temperature. Relative to NaX and Ni-MOF-74, ZIF-7 and SBMOF-1 show strong CO₂ affinity even in the presence of 75% RH and may be more ideally suited for postcombustion flue gas CO₂ capture than compounds with unsaturated metal sites. XRD-DSC is particularly powerful for evaluating the consequences of framework flexibility, with XRD providing the signature indicative of the structural rearrangement and the DSC providing the enthalpies of adsorption for each structure. This kind of detailed energy evaluation is not possible with other noncalorimetric methods

Phase Behavior of Alkyne-Functionalized Styrenic Block Copolymer/Cobalt Carbonyl Adducts and <i>in Situ</i> Formation of Magnetic Nanoparticles by Thermolysis

A series of polystyrene-<i>block</i>-poly­(4-(phenyl­ethynyl)­styrene) (PS-<i>b</i>-PPES) diblock copolymers with a range of compositions were prepared by reversible addition–fragmentation chain transfer (RAFT) polymerization. Block copolymer/cobalt carbonyl adducts (PS_<i>x</i>-PPES_<i>y</i>[Co₂(CO)₆]_<i>n</i>) were subsequently prepared by reaction of Co₂(CO)₈ with the alkyne groups of the PPES block. Phase behavior of the block copolymer/cobalt carbonyl adducts (PS_<i>x</i>-PPES_<i>y</i>[Co₂(CO)₆]_<i>n</i>, 8% ≤ wt % PS ≤ 68%) was studied by small-angle X-ray scattering and transmission electron microscopy (TEM). As the composition of PS_<i>x</i>-PPES_<i>y</i>[Co₂(CO)₆]_<i>n</i> copolymers was shifted from PS as the majority block to PPES_<i>y</i>[Co₂(CO)₆]_<i>n</i> as the majority block, the morphology was observed to shift from lamellar with larger PS domains to cylindrical with PS as the minority component and then to spherical with PS as the minority component. These observations have been used to map out a partial phase diagram for PS_<i>x</i>-PPES_<i>y</i>[Co₂(CO)₆]_<i>n</i> diblock copolymers. Heating of PS_<i>x</i>-PPES_<i>y</i>[Co₂(CO)₆]_<i>n</i> samples at relatively low temperatures (120 °C) results in the formation of nanoparticles containing crystalline cobalt and cobalt oxide domains within the PPES_<i>y</i>[Co₂(CO)₆]_<i>n</i> regions as characterized by TEM, X-ray diffraction (XRD), and X-ray scattering

Light Hydrocarbon Adsorption Mechanisms in Two Calcium-Based Microporous Metal Organic Frameworks

The adsorption mechanism of ethane, ethylene, and acetylene (C₂H_<i>n</i>; <i>n</i> = 2, 4, 6) on two microporous metal organic frameworks (MOFs) is described here that is consistent with observations from single crystal and powder X-ray diffraction, calorimetric measurements, and gas adsorption isotherm measurements. Two calcium-based MOFs, designated as SBMOF-1 and SBMOF-2 (SB: Stony Brook), form three-dimensional frameworks with one-dimensional open channels. As determined from single crystal diffraction experiments, channel geometries of both SBMOF-1 and SBMOF-2 provide multiple adsorption sites for hydrocarbon molecules through C–H···π and C–H···O interactions, similarly to interactions in the molecular and protein crystals. Both materials selectively adsorb C₂ hydrocarbon gases over methane as determined with IAST and breakthrough calculations as well as experimental breakthrough measurements, with C₂H₆/CH₄ selectivity as high as 74 in SBMOF-1

Magnetic Hydrogels from Alkyne/Cobalt Carbonyl-Functionalized ABA Triblock Copolymers

A series of alkyne-functionalized poly­(4-(phenylethynyl)­styrene)-<i>block</i>-poly­(ethylene oxide)-<i>block</i>-poly­(4-(phenylethynyl)­styrene) (PPES-<i>b</i>-PEO-<i>b-</i>PPES) ABA triblock copolymers was synthesized by reversible addition–fragmentation chain transfer (RAFT) polymerization. PES_<i>n</i>[Co₂(CO)₆]_<i>x</i>-EO₈₀₀-PES_<i>n</i>[Co₂(CO)₆]_<i>x</i> ABA triblock copolymer/cobalt adducts (10–67 wt % PEO) were subsequently prepared by reaction of the alkyne-functionalized PPES block with Co₂(CO)₈ and their phase behavior was studied by TEM. Heating triblock copolymer/cobalt carbonyl adducts at 120 °C led to cross-linking of the PPES/Co domains and the formation of magnetic cobalt nanoparticles within the PPES/Co domains. Magnetic hydrogels could be prepared by swelling the PEO domains of the cross-linked materials with water. Swelling tests, rheological studies and actuation tests demonstrated that the water capacity and modulus of the hydrogels were dependent upon the composition of the block copolymer precursors

Iodine Adsorption in Metal Organic Frameworks in the Presence of Humidity

Used nuclear fuel reprocessing represents a unique challenge when dealing with radionuclides such as isotopes of ⁸⁵Kr and ¹²⁹I₂ due to their volatility and long half-life. Efficient capture of ¹²⁹I₂ (<i>t</i>_1/2 = 15.7 × 10⁶ years) from the nuclear waste stream can help reduce the risk of releasing I₂ radionuclide into the environment and/or potential incorporation into the human thyroid. Metal organic frameworks have the reported potential to be I₂ adsorbents but the effect of water vapor, generally present in the reprocessing off-gas stream, is rarely taken into account. Moisture-stable porous metal organic frameworks that can selectively adsorb I₂ in the presence of water vapor are thus of great interest. Herein, we report on the I₂ adsorption capacity of two microporous metal organic frameworks at both dry and humid conditions. Single-crystal X-ray diffraction and Raman spectroscopy reveal distinct sorption sites of molecular I₂ within the pores in proximity to the phenyl- and phenol-based linkers stabilized by the I···π and I···O interactions, which allow selective uptake of iodine

Iodine Adsorption in Metal Organic Frameworks in the Presence of Humidity

Used nuclear fuel reprocessing represents a unique challenge when dealing with radionuclides such as isotopes of ⁸⁵Kr and ¹²⁹I₂ due to their volatility and long half-life. Efficient capture of ¹²⁹I₂ (<i>t</i>_1/2 = 15.7 × 10⁶ years) from the nuclear waste stream can help reduce the risk of releasing I₂ radionuclide into the environment and/or potential incorporation into the human thyroid. Metal organic frameworks have the reported potential to be I₂ adsorbents but the effect of water vapor, generally present in the reprocessing off-gas stream, is rarely taken into account. Moisture-stable porous metal organic frameworks that can selectively adsorb I₂ in the presence of water vapor are thus of great interest. Herein, we report on the I₂ adsorption capacity of two microporous metal organic frameworks at both dry and humid conditions. Single-crystal X-ray diffraction and Raman spectroscopy reveal distinct sorption sites of molecular I₂ within the pores in proximity to the phenyl- and phenol-based linkers stabilized by the I···π and I···O interactions, which allow selective uptake of iodine

Growth of Nanoparticles with Desired Catalytic Functions by Controlled Doping-Segregation of Metal in Oxide

The size and morphology of metal nanoparticles (NPs) often play a critical role in defining the catalytic performance of supported metal nanocatalysts. However, common synthetic methods struggle to produce metal NPs of appropriate size and morphological control. Thus, facile synthetic methods that offer controlled catalytic functions are highly desired. Here we have identified a new pathway to synthesize supported Rh nanocatalysts with finely tuned spatial dimensions and controlled morphology using a doping-segregation method. We have analyzed their structure evolutions during both the segregation process and catalytic reaction using a variety of in situ spectroscopic and microscopic techniques. A correlation between the catalytic functional sites and activity in CO₂ hydrogenation over supported Rh nanocatalysts is then established. This study demonstrates a facile strategy to design and synthesize nanocatalysts with desired catalytic functions