A Cationic Antimonite Chain Templated by Sulfate: [Sb₆O₇⁴⁺][(SO₄^2–)₂]

An extended metal oxide possessing a cationic charge on the host has been synthesized by hydrothermal methods. The structure consists of 1D antimony oxide [Sb₆O₇]⁴⁺ chains with a new structural motif of four Sb atoms wide and unprotonated sulfate anions between the chains. The material was characterized by powder and single-crystal X-ray diffraction. Thermal behavior and chemical resistance in aqueous acidic conditions (pH ∼2) indicate a highly stable cationic material. The stability is attributed to the entirely inorganic composition of the structure, where 1D covalently extended chains are electrostatically bound to divalent anions

Anion Exchange of the Cationic Layered Material [Pb₂F₂]²⁺

We demonstrate the complete exchange of the interlamellar anions of a 2-D cationic inorganic material. The α,ω-alkanedisulfonates were exchanged for α,ω-alkanedicarboxylates, leading to two new cationic materials with the same [Pb₂F₂]²⁺ layered architecture. Both were solved by single crystal X-ray diffraction and the transformation also followed by in situ optical microscopy and ex situ powder X-ray diffraction. This report represents a rare example of metal–organic framework displaying highly efficient and complete replacement of its anionic organic linker while retaining the original extended inorganic layer. It also opens up further possibilities for introducing other anions or abatement of problematic anions such as pharmaceuticals and their metabolites

A Cationic Antimonite Chain Templated by Sulfate: [Sb₆O₇⁴⁺][(SO₄^2–)₂]

An extended metal oxide possessing a cationic charge on the host has been synthesized by hydrothermal methods. The structure consists of 1D antimony oxide [Sb₆O₇]⁴⁺ chains with a new structural motif of four Sb atoms wide and unprotonated sulfate anions between the chains. The material was characterized by powder and single-crystal X-ray diffraction. Thermal behavior and chemical resistance in aqueous acidic conditions (pH ∼2) indicate a highly stable cationic material. The stability is attributed to the entirely inorganic composition of the structure, where 1D covalently extended chains are electrostatically bound to divalent anions

A Cationic Metal–Organic Solid Solution Based on Co(II) and Zn(II) for Chromate Trapping

We report the synthesis and characterization of a solid solution series of cationic metal–organic materials with full compositional range from pure Co­(II) to Zn­(II) end-members. The materials consist of [Zn_<i>x</i>­Co_1–<i>x</i>­(H₂O)₄­(4,4′-bipy)₂]²⁺ metal–organic clusters that π–π stack into 2-D positively charged layers, with the metal ratio tunable by molar ratio under hydrothermal conditions. The interlamellar α,ω-alkane­disulfonate serves as an anionic template and noncovalently interacts with the cationic layers. The weak interaction allows anion exchange for toxic oxometal anions, such as chromate, CrO₄^2–. The highest chromate adsorption capacity was 68.5 mg/g (0.43 mol/mol) for the as-synthesized 50 mol % Co­(II)-incorporated material. Our cationic material can also selectively trap these toxic oxo-anions when nontoxic anions (e.g., nitrate, sulfate) were present in an over 50-fold excess concentration

Light-Triggered Eradication of Acinetobacter baumannii by Means of NO Delivery from a Porous Material with an Entrapped Metal Nitrosyl

A photoactive manganese nitrosyl, namely [Mn­(PaPy₃)­(NO)]­(ClO₄) ({Mn-NO}), has been loaded into the columnar pores of an MCM-41 host. Strong interaction between the polar nitrosyl and the −OH groups on the host wall leads to excellent entrapment of the NO donor within the porous host. With the aluminosilicate-based host (Al-MCM-41), the loading is further enhanced due to electrostatic interaction of the cationic species with the aluminum sites. The extent of loading has been determined via analytical techniques including N₂ adsorption/desorption isometry. Powder X-ray diffraction studies on the loaded materials afford patterns typical of an ordered mesoporous silicate consisting of a hexagonal array of unidimensional channels (with slight loss of crystallinity). Elemental mapping of the loaded particles confirms the incorporation of {Mn-NO} into the porous MCM-41 structure and attests to the homogeneity of the guest molecule distribution throughout individual particles. When suspensions of the loaded materials in saline solution are exposed to low-power (10–100 mW) visible light, rapid release of NO is observed. With continuous exposure, a steady release of 50–80 μM of NO is attained with 5 mg of material/mL buffer within 5 min, and the NO flux is maintained for a period of ∼60 min. Rapid bursts of 5–10 μM NO are noted with short light pulses. Loss of either the nitrosyl or its photoproduct(s) from these materials in biological media is minimal over long periods of time. The NO release profiles suggest potential use of these powdery biocompatible materials as NO donors where the delivery of NO (a strong antibiotic) could be controlled via the exposure of light. Such prediction has been confirmed with the successful eradication of both drug-susceptible and drug-resistant Acinetobacter baumannii in a soft-tissue infection model through light-triggered NO delivery

A Robust Sulfonate-Based Metal–Organic Framework with Permanent Porosity for Efficient CO₂ Capture and Conversion

We report a rare example of a sulfonate-based metal–organic framework (MOF) possessing a prototypical primitive-cubic topology, constructed with Jahn–Teller distorted Cu­(II) centers and a mixed-linker (organosulfonate and N-donor) system. The inherent highly polar, permanent porosity contributes to the highest reported CO₂ sorption properties to date among organosulfonate-based MOFs, outperforming the benchmark carboxylate MOF counterpart. Importantly, density functional theory calculations confirm that the CO₂–sulfonate interaction plays an important role in CO₂ capture. Indeed, the hydrothermal product demonstrates high robustness over a wide pH range as well as aqueous boiling conditions, overcoming the moisture sensitivity of conventional Cu₂ paddlewheel-based MOFs. In addition, bulk synthesis of this material has been successfully achieved on a gram scale (>1 g) in a single batch with a high yield. Combining the high CO₂ affinity and a robust nature, this sulfonate porous material is also an efficient, recyclable heterogeneous catalyst for CO₂ fixation to form cyclic carbonates under ambient conditions

A Cationic Metal–Organic Solid Solution Based on Co(II) and Zn(II) for Chromate Trapping

We report the synthesis and characterization of a solid solution series of cationic metal–organic materials with full compositional range from pure Co­(II) to Zn­(II) end-members. The materials consist of [Zn_<i>x</i>­Co_1–<i>x</i>­(H₂O)₄­(4,4′-bipy)₂]²⁺ metal–organic clusters that π–π stack into 2-D positively charged layers, with the metal ratio tunable by molar ratio under hydrothermal conditions. The interlamellar α,ω-alkane­disulfonate serves as an anionic template and noncovalently interacts with the cationic layers. The weak interaction allows anion exchange for toxic oxometal anions, such as chromate, CrO₄^2–. The highest chromate adsorption capacity was 68.5 mg/g (0.43 mol/mol) for the as-synthesized 50 mol % Co­(II)-incorporated material. Our cationic material can also selectively trap these toxic oxo-anions when nontoxic anions (e.g., nitrate, sulfate) were present in an over 50-fold excess concentration

Rapid Eradication of Human Breast Cancer Cells through Trackable Light-Triggered CO Delivery by Mesoporous Silica Nanoparticles Packed with a Designed photoCORM

The surprising discovery of salutary effects of low doses of carbon monoxide (CO) in mammalian physiology has raised intense research interest in CO delivery to biological targets under controlled conditions. In recent attempts, photoactive metal carbonyl complexes (photoCORMs) have been employed to trigger CO release at the target sites. In this work, a designed photoCORM namely, <i>fac</i>-[Re­(CO)₃(pbt) (PPh₃)]­(CF₃SO₃) (<b>1</b>, pbt =2-(2-pyridyl)­benzothiazole) has been synthesized and characterized by spectroscopic methods and crystallography. This photoCORM not only releases CO upon illumination with low-power UV light (305 nm, 5 mW cm^–2) but also exhibits a “turn-off” of its orange luminescence (λ_em = 605 nm) upon release of one CO ligand. The latter property provides a convenient way to track the CO release event. The photoCORM <b>1</b> has been entrapped within the pores of the narrow channels of 100 nm mesoporous Al-MCM-41 nanoparticles and the loaded {Re-CO}@Al-MCM-41 MSNs have been characterized by powder X-ray diffraction (PXRD), FTIR spectroscopy and chemical analysis. Results of scanning electron microscopy (SEM), transmission electron microscopy (TEM), and the SEM-EDX elemental maps of C, Si, O, Re, and P confirm that the carbonyl complex is retained within the pores of the MSNs. Strong electrostatic binding of the cationic photoCORM to the negatively charged walls of the Al-MCM-41 nanoparticles results in very little leaching of the CO donor from the host matrix. The hydrodynamic parameters (155 nm diameter in PBS, ζ-potential = −28.53 ± 1.00 mV) of the biocompatible {Re-CO}@Al-MCM-41 MSNs fall in the right range of the drug-carriers and the particles are readily endocytosed by MDA-MB-231 (human breast cancer) cells. The entry of the {Re-CO}@Al-MCM-41 MSNs into the cellular matrix is easily visualized by the intense orange luminescence (λ_ex = 400 nm) of the loaded cells. Short exposure of the cells to low-power UV light brings about a rapid diminution of the orange luminescence due to CO release from the photoCORM locked within the MSNs and causes CO-induced death of the cancer cells. Recently, CO has been shown to induce apoptotic death in different types of cancer cells as well as enhance the efficacy of cancer chemotherapy. The simple design of the {Re-CO}@Al-MCM-41 MSNs and their response to light allows for the first time to deliver the drug (CO) from a pro-drug locked within a biocompatible MSNs that can readily accumulate within malignant sites due to the “enhance permeability and retention” (EPR) effect. In addition, the CO delivery process can be conveniently tracked through the loss of luminescence of the MSNs

A Robust Sulfonate-Based Metal–Organic Framework with Permanent Porosity for Efficient CO₂ Capture and Conversion

We report a rare example of a sulfonate-based metal–organic framework (MOF) possessing a prototypical primitive-cubic topology, constructed with Jahn–Teller distorted Cu­(II) centers and a mixed-linker (organosulfonate and N-donor) system. The inherent highly polar, permanent porosity contributes to the highest reported CO₂ sorption properties to date among organosulfonate-based MOFs, outperforming the benchmark carboxylate MOF counterpart. Importantly, density functional theory calculations confirm that the CO₂–sulfonate interaction plays an important role in CO₂ capture. Indeed, the hydrothermal product demonstrates high robustness over a wide pH range as well as aqueous boiling conditions, overcoming the moisture sensitivity of conventional Cu₂ paddlewheel-based MOFs. In addition, bulk synthesis of this material has been successfully achieved on a gram scale (>1 g) in a single batch with a high yield. Combining the high CO₂ affinity and a robust nature, this sulfonate porous material is also an efficient, recyclable heterogeneous catalyst for CO₂ fixation to form cyclic carbonates under ambient conditions

IRMOF Thin Films Templated by Oriented Zinc Oxide Nanowires

We present a new method in the synthesis of metal–organic framework (MOF) thin films using zinc oxide nanowires as the substrate. This facile method involves growing zinc oxide nanowires on a substrate (glass, transparent conducting oxide glass, Si wafer), followed by immersing the nanowire substrate in an iso-reticular metal–organic framework (IRMOF) precursor solution. The resulting 25 μm thick film is highly crystalline and covers the entire substrate. Growth of the IRMOF on the nanowire substrate allows for the film to be used in potential applications in sensing, membranes, photovoltaics, catalysis, and gas storage. We have also successfully used microwaves to rapidly produce these films with comparable film quality to our original method