"Activated Borane": A Porous Borane Cluster Polymer as an Efficient Lewis Acid-Based Catalyst.

Borane cluster-based porous covalent networks, named activated borane (ActB), were prepared by cothermolysis of decaborane(14) (nido-B10H14) and selected hydrocarbons (toluene, ActB-Tol; cyclohexane, ActB-cyHx; and n-hexane, ActB-nHx) under anaerobic conditions. These amorphous solid powders exhibit different textural and Lewis acid (LA) properties that vary depending on the nature of the constituent organic linker. For ActB-Tol, its LA strength even approaches that of the commonly used molecular LA, B(C6F5)3. Most notably, ActBs can act as heterogeneous LA catalysts in hydrosilylation/deoxygenation reactions with various carbonyl substrates as well as in the gas-phase dehydration of ethanol. These studies reveal the potential of ActBs in catalytic applications, showing (a) the possibility for tuning catalytic reaction outcomes (selectivity) in hydrosilylation/deoxygenation reactions by changing the material's composition and (b) the very high activity toward ethanol dehydration that exceeds the commonly used γ-Al2O3 by achieving a stable conversion of ∼93% with a selectivity for ethylene production of ∼78% during a 17 h continuous period on stream at 240 °C.

Linker-Functionalized Phosphinate Metal-Organic Frameworks: Adsorbents for the Removal of Emerging Pollutants.

Metal-organic frameworks (MOFs) are attracting increasing attention as adsorbents of contaminants of emerging concern that are difficult to remove by conventional processes. This paper examines how functional groups covering the pore walls of phosphinate-based MOFs affect the adsorption of specific pharmaceutical pollutants (diclofenac, cephalexin, and sulfamethoxazole) and their hydrolytic stability. New structures, isoreticular to the phosphinate MOF ICR-7, are presented. The phenyl ring facing the pore wall of the presented MOFs is modified with dimethylamino groups (ICR-8) and ethyl carboxylate groups (ICR-14). These functionalized MOFs were obtained from two newly synthesized phosphinate linkers containing the respective functional groups. The presence of additional functional groups resulted in higher affinity toward the tested pollutants compared to ICR-7 or activated carbon. However, this modification also comes with a reduced adsorption capacity. Importantly, the introduction of the functional groups enhanced the hydrolytic stability of the MOFs.

"Activated Borane" - A Porous Borane Cluster Network as an Effective Adsorbent for Removing Organic Pollutants.

The unprecedented co-thermolysis of decaborane(14) (nido-B10 H14 ) and toluene results in a novel porous material (that we have named "activated borane") containing micropores between 1.0 and 1.5 nm in diameter and a specific surface area of 774 m2 g-1 (Ar, 87 K) that is thermally stable up to 1000 °C. Solid state 1 H, 11 B and 13 C MAS NMR, UV-vis and IR spectroscopies suggest an amorphous structure of borane clusters interconnected by toluene moieties in a ratio of about three toluene molecules for every borane cluster. In addition, the structure contains Lewis-acidic tri-coordinated boron sites giving it some unique properties. Activated borane displays high sorption capacity for pollutants such as sulfamethoxazole, tramadol, diclofenac and bisphenol A that exceed the capacity of commercially-available activated carbon. The consistency in properties for each batch made, and the ease of its synthesis, make activated borane a promising porous material worthy of broad attention.

Robust Aluminum and Iron Phosphinate Metal-Organic Frameworks for Efficient Removal of Bisphenol A.

Porous metal-organic frameworks (MOFs) have excellent characteristics for the adsorptive removal of environmental pollutants. Herein, we introduce a new series of highly stable MOFs constructed using Fe3+ and Al3+ metal ions and bisphosphinate linkers. The isoreticular design leads to ICR-2, ICR-6, and ICR-7 MOFs with a honeycomb arrangement of linear pores, surface areas up to 1360 m2 g-1, and high solvothermal stabilities. In most cases, their sorption capacity is retained even after 24 h of reflux in water. The choice of the linkers allows for fine-tuning of the pore sizes and the chemical nature of the pores. This feature can be utilized for the optimization of host-guest interactions between molecules and the pore walls. Water pollution by various endocrine disrupting chemicals has been considered a global threat to public health. In this work, we prove that the chemical stability and hydrophobic nature of the synthesized series of MOFs result in the remarkable sorption properties of these materials for endocrine disruptor bisphenol A.

Zirconium Metal-Organic Framework UiO-66: Stability in an Aqueous Environment and Its Relevance for Organophosphate Degradation.

Zirconium-based metal-organic frameworks were recently investigated as catalysts for degradation of organophosphate toxic compounds, such as pesticides or chemical warfare agents. The most utilized UiO-66 is considered as a stable material for these applications in an aqueous environment. However, the presented results indicate that the properties of UiO-66 are changing considerably in aqueous media under common conditions used for organophosphate degradations, and therefore its catalytic activity is not related to the number of structural defects created during the material synthesis. We delineate the stability of UiO-66 in water of various pHs, the in situ formation of new catalytic sites, and the correlation of these two parameters with the degradation rate of a model organophosphate pollutant, dimethyl-4-nitrophenyl phosphate (methyl-paraoxon). The stability was quantified using high-performance liquid chromatography (HPLC) by measuring the amounts of leached terephthalic acid, the linker of UiO-66, and monocarboxylic acids, the modulators bound at UiO-66 defects. We demonstrate that the HPLC analysis is a more suitable method for metal-organic frameworks stability assessment than commonly used methods, e.g., powder X-ray diffraction, adsorption isotherms, or electron microscopy.

Nanoscaled porphyrinic metal-organic frameworks: photosensitizer delivery systems for photodynamic therapy.

The photocytotoxic activity of porphyrin-containing materials including metal-organic frameworks (MOFs) has attracted ever increasing interest. We have developed a simple synthesis of hexagonal PCN-222/MOF-545 nanoparticles, which are powerful in inducing reactive oxygen species-mediated apoptosis of cancer cells upon visible light irradiation. The extent of the cytotoxic effect well correlates with the nanoparticle size and structural instability. High phototoxicity of the presented nanoparticles and their deactivation within several hours open up the door to possible applications in cancer therapy.