Group 13 Metal Carboxylates: Using Molecular Clusters As Hybrid Building Units in a MIL-53 Type Framework

Systematic investigation of the reactions of the system AlCl₃·6H₂O/pyridine-2,4,6-tricarboxylic acid (H₃<b>PTC</b>)/pyridine in water yielded two new compounds, both containing the dimeric {Al<b>PTC</b>(μ-OH)­(H₂O)}₂^2– unit. With long reaction times, the framework compound [Al­(μ-OH)­{Al<b>PTC</b>(μ-OH)­(H₂O)}₂]·2H₂O (CAU-16, compound <b>1</b>) is obtained, the first example of a framework compound with a metal–organic cluster linker, and bearing the MIL-53 network. Although the compound does not breathe, as other MIL-53 compounds do, it has a maximum uptake of CO₂ of 1.76(2) mmol g^–1 at 196 K. With shorter reaction times, the molecular compound {Al­(H<b>PTC</b>)­(μ-OH)­(H₂O)}₂ (<b>2</b>) was prepared, leading to the proposal of a crystallization scheme for the Al³⁺-pyridine-2,4,6,-tricarboxylic acid system. To determine whether further framework compounds bearing hybrid metal cluster linkers could be prepared, systematic high-throughput investigations of pyridine-2,4,6-tricarboxylic acid in water with Ga³⁺ and In³⁺ were undertaken. These yielded two chain-type compounds, Ga<b>PTC</b>(H₂O)₂ (<b>3</b>) and In<b>PTC</b>(H₂O)₂ (<b>4</b>), with different coordination chemistries. Optimized syntheses for compounds <b>1</b>, <b>2</b>, and <b>4</b> are reported

Group 13 Metal Carboxylates: Using Molecular Clusters As Hybrid Building Units in a MIL-53 Type Framework

Systematic investigation of the reactions of the system AlCl₃·6H₂O/pyridine-2,4,6-tricarboxylic acid (H₃<b>PTC</b>)/pyridine in water yielded two new compounds, both containing the dimeric {Al<b>PTC</b>(μ-OH)­(H₂O)}₂^2– unit. With long reaction times, the framework compound [Al­(μ-OH)­{Al<b>PTC</b>(μ-OH)­(H₂O)}₂]·2H₂O (CAU-16, compound <b>1</b>) is obtained, the first example of a framework compound with a metal–organic cluster linker, and bearing the MIL-53 network. Although the compound does not breathe, as other MIL-53 compounds do, it has a maximum uptake of CO₂ of 1.76(2) mmol g^–1 at 196 K. With shorter reaction times, the molecular compound {Al­(H<b>PTC</b>)­(μ-OH)­(H₂O)}₂ (<b>2</b>) was prepared, leading to the proposal of a crystallization scheme for the Al³⁺-pyridine-2,4,6,-tricarboxylic acid system. To determine whether further framework compounds bearing hybrid metal cluster linkers could be prepared, systematic high-throughput investigations of pyridine-2,4,6-tricarboxylic acid in water with Ga³⁺ and In³⁺ were undertaken. These yielded two chain-type compounds, Ga<b>PTC</b>(H₂O)₂ (<b>3</b>) and In<b>PTC</b>(H₂O)₂ (<b>4</b>), with different coordination chemistries. Optimized syntheses for compounds <b>1</b>, <b>2</b>, and <b>4</b> are reported

Mechanical Properties of a Calcium Dietary Supplement, Calcium Fumarate Trihydrate

The mechanical properties of calcium fumarate trihydrate, a 1D coordination polymer considered for use as a calcium source for food and beverage enrichment, have been determined via nanoindentation and high-pressure X-ray diffraction with single crystals. The nanoindentation studies reveal that the elastic modulus (16.7–33.4 GPa, depending on crystallographic orientation), hardness (1.05–1.36 GPa), yield stress (0.70–0.90 GPa), and creep behavior (0.8–5.8 nm/s) can be rationalized in view of the anisotropic crystal structure; factors include the directionality of the inorganic Ca–O–Ca chain and hydrogen bonding, as well as the orientation of the fumarate ligands. High-pressure single-crystal X-ray diffraction studies show a bulk modulus of ∼20 GPa, which is indicative of elastic recovery intermediate between small molecule drug crystals and inorganic pharmaceutical ingredients. The combined use of nanoindentation and high-pressure X-ray diffraction techniques provides a complementary experimental approach for probing the critical mechanical properties related to tableting of these dietary supplements

Phase Transitions in Zeolitic Imidazolate Framework 7: The Importance of Framework Flexibility and Guest-Induced Instability

Phase Transitions in Zeolitic Imidazolate Framework 7: The Importance of Framework Flexibility and Guest-Induced Instabilit

Phase Transitions in Zeolitic Imidazolate Framework 7: The Importance of Framework Flexibility and Guest-Induced Instability

Phase Transitions in Zeolitic Imidazolate Framework 7: The Importance of Framework Flexibility and Guest-Induced Instabilit

Pressure Promoted Low-Temperature Melting of Metal-Organic Frameworks

Metal-organic frameworks (MOFs) are microporous materials with huge potential as host structures for chemical processes, including retention, catalytic reaction, or separation of guest molecules. Structural collapse at high-pressure, and unusual behaviours at elevated temperatures, such as melting and transitions to liquid states, have recently been observed in the family. Here, we show that the effect of the application of simultaneous high-pressure and -temperature on a MOF can be understood in terms of silicate analogues, with crystalline, amorphous and liquid states occurring across the pressure - temperature phase diagram. The response of ZIF-62, the MOF on which we focus, to simultaneous pressure and temperature reveals a complex behaviour with distinct high- and low- density amorphous phases occurring over different regions of the pressure-temperature space. In-situ powder X-ray diffraction, Raman spectroscopy and optical microscopy reveal that the stability of the liquid MOF-state expands significantly towards lower temperatures at intermediate, industrially achievable pressures. Our results imply a novel route to the synthesis of functional MOF glasses at low temperatures, avoiding decomposition upon heating at ambient pressure