Boosting Photocatalytic Hydrogen Production by MOF-derived Metal Oxide Heterojunctions with a 10.0% Apparent Quantum Yield.

Photocatalytic hydrogen production offers an alternative pathway to establish a sustainable energy economy. While numerous photoactive materials exhibit potential for generating hydrogen from water, the synergy achieved by combining two different materials with complementary properties in the form of heterojunctions can significantly their photocatalytic activity. Our study describes the design and generation of the metal-organic framework-derived (MOF) metal oxide heterojunction composed of RuO2/N,S-TiO2. The RuO2/N,S-TiO2 is generated through the pyrolysis of MOFs, Ru- HKUST-1, and the amino-functionalized MIL-125-NH2. Among the various RuO2/N,S- TiO2 materials tested, the material characterized by the lowest RuO2 content, exhibited the highest hydrogen evolution rate, producing 10,761 µmol·hr-1·g-1 of hydrogen with an apparent quantum-yield of 10.0% in pure water. In addition to RuO2/N,S-TiO2, we generated two other MOF-derived metal-oxide heterojunctions, ZnO/N,S-TiO2 and In2O3/N,S-TiO2, leading to apparent quantum yields of 0.7% and 0.3%, respectively. The remarkable photocatalytic activity observed in RuO2/N,S-TiO2 is thought to be attributed to the synergistic effects arising from the combination of metallic properties inherent in the metal oxides, their band alignment, porosity, and surface properties inherited from the parent MOFs. The photocatalytic efficiency of RuO2/N,S-TiO2 was further demonstrated in actual water samples, producing hydrogen with a rate of 8,190 µmol·hr-1·g-1 in tap water.

Hypsochromically-shifted Emission of Metal-organic Frameworks Generated through Post-synthetic Ligand Reduction.

Luminescent materials with tunable emission are becoming increasingly desirable as we move towards needing efficient Light Emitting Diodes (LEDs) for displays. Key to developing better displays is the advancement of strategies for rationally designing emissive materials that are tunable and efficient. We report a series of emissive metal-organic frameworks (MOFs) generated using BUT-10 (BUT: Beijing University of Technology) that emits green light with λmax at 525 nm. Post-synthetic reduction of the ketone on the fluorenone ligand in BUT-10 generates new materials, BUT-10-M and BUT-10-R. The emission for BUT-10-R is hypsochromically-shifted by 113 nm. Multivariate BUT-10-M structures demonstrate emission with two maxima corresponding to the emission of both fluorenol and fluorenone moieties present in their structures. Our study represents a novel post-synthetic ligand reduction strategy for producing emissive MOFs with tunable emission ranging from green, white-blue to deep blue.

Formation and Redox Interconversion of Niobium Methylidene and Methylidyne Complexes.

The niobium methylidene [{(Ar'O)2 Nb}2 (µ2 -Cl)2 (µ2 -CH2 )] (2) can be cleanly prepared via thermolysis or photolysis of [(Ar'O)2 Nb(CH3 )2 Cl] (1) (OAr'=2,6-bis(diphenylmethyl)-4-tert-butylphenoxide). Reduction of 2 with two equivalents of KC8 results in formation of the first niobium methylidyne [K][{(Ar'O)2 Nb}2 (µ2 -CH)(µ2 -H)(µ2 -Cl)] (3) via a binuclear α-hydrogen elimination. Oxidation of 3 with two equiv of ClCPh3 reforms 2. In addition to solid state X-ray analysis, all these complexes were elucidated via multinuclear NMR experiments and isotopic labelling studies, including a crossover experiment, support the notion for a radical mechanism as well as a binuclear α-hydrogen abstraction pathway being operative in the formation of 2 from 1.

Cyclo-P3 Complexes of Vanadium: Redox Properties and Origin of the ³¹P NMR Chemical Shift.

The synthesis and characterization of two high-valent vanadium-cyclo-P3 complexes, (nacnac)V(cyclo-P3)(Ntolyl2) (1) and (nacnac)V(cyclo-P3)(OAr) (2), and an inverted sandwich derivative, [(nacnac)V(Ntolyl2)]2(µ2-η(3):η(2)-cyclo-P3) (3), are presented. These novel complexes are prepared by activating white phosphorus (P4) with three-coordinate vanadium(II) precursors. Structural metrics, redox behavior, and DFT electronic structure analysis indicate that a [cyclo-P3](3-) ligand is bound to a V(V) center in monomeric species 1 and 2. A salient feature of these new cyclo-P3 complexes is their significantly downfield shifted (by ∼300 ppm) (31)P NMR resonances, which is highly unusual compared to related complexes such as (Ar[(i)Pr]N)3Mo(cyclo-P3) (4) and other cyclo-P3 complexes that display significantly upfield shifted resonances. This NMR spectroscopic signature was thus far thought to be a diagnostic property for the cyclo-P3 ligand related to its acute endocyclic angle. Using DFT calculations, we scrutinized and conceptualized the origin of the unusual chemical shifts seen in this new class of complexes. Our analysis provides an intuitive rational paradigm for understanding the experimental (31)P NMR spectroscopic signature by relating the nuclear magnetic shielding with the electronic structure of the molecule, especially with the characteristics of metal-cyclo-P3 bonding.

Multivariate metal-organic frameworks generated through post-synthetic modification: impact and future directions.

Reticular chemistry has proven to be invaluable over time, thanks to the structural versatility, and tailored porosity observed in structures like metal-organic frameworks (MOFs), covalent-organic frameworks (COFs), and metal-organic polyhedra (MOPs). Despite the wide array of ligands and metals available for synthesizing MOFs, they are still somewhat constrained by the reliance on de novo conditions and the focus on generating MOFs with single ligand and metal. To surpass these limitations, researchers have established strategies to generate multivariate (MTV) MOF structures incorporating more than one ligand/metal into the crystal lattice. MTV-MOFs have demonstrated enhanced properties by virtue of the additional functionalities incorporated within their structures. One approach to developing MTV-MOFs is through post-synthetic modification (PSM), where new functionalities are introduced after the initial synthesis, thereby achieving the enhanced properties of MTV-MOFs even in cases where the new functionalities are incompatible with MOF synthesis.

Colorimetric detection of acidic pesticides in water.

A water-stable, porphyrin-based metal-organic framework (MOF) produces a distinct colour change in response to acids' pKa and concentrations. This colour change is associated with the protonation of the N-atoms within the porphyrin ligand present in the MOF structure. As a proof-of-concept, we demonstrate the use of this MOF for detecting traces of different acidic pesticides present in water samples spontaneously.

Access Is Necessary but Not Sufficient: Factors Influencing Delay and Avoidance of Health Care Services.

Background: Despite recently expanded access to health insurance, consumers still face barriers to using their coverage to obtain needed health care. Objective: To examine the characteristics of those who delay or avoid health care due to costs. Methods: Participants were recruited via Amazon MTurk and completed a survey assessing demographic characteristics, financial toxicity, health care minimizer-maximizer tendencies, health insurance knowledge, numeracy, delaying/avoiding any care, and delaying/avoiding six common health care services (three preventive and three nonpreventive services). Validated measures were used when available. Delay/avoidance behaviors were categorized into delaying/avoiding any care, preventive care, and nonpreventive care. Logistic regression models examined 1) financial toxicity, 2) minimizer-maximizer tendencies, 3) numeracy, 4) health insurance knowledge, and 5) knowledge of preventive care coverage separately on three forms of delay/avoidance behaviors, controlling for chronic conditions, insurance status, and/or income where appropriate. Results: Of 518 respondents, 470 did not fail attention-check questions and were used in analyses. Forty-five percent of respondents reported delaying/avoiding care due to cost. Multivariable analyses found that financial toxicity was related to delaying/avoiding any care (odds ratio [OR] = 0.884, P < 0.001), preventive care (OR = 0.906, P < 0.001), and nonpreventive care (OR = 0.901, P < 0.001). A tendency to minimize seeking health care (OR = 0.734, P < 0.001) and lower subjective numeracy (OR = 0.794, P = 0.023) were related to delaying/avoiding any care. General health insurance knowledge (OR = 0.989, P = 0.023) and knowledge of preventive care coverage (OR = 0.422, P < 0.001) were related to delaying/avoiding preventive care. Conclusions: Many people delay or avoid health care due to costs, even when insured. Results suggest that there may be different reasons individuals delay or avoid preventive and nonpreventive care. Findings may inform interventions to educate consumers and support discussions about health care costs to facilitate appropriate health care utilization.

Parents' adherence to pediatric health and safety guidelines: Importance of patient-provider relationships.

OBJECTIVE: To examine 1) parent-provider communication about pediatric health/safety guidelines, 2) trust in child's provider, 3) comfort discussing guidelines, 4) agreement with guideline advice, 5) self-efficacy following guidelines, and their impact on guideline adherence. METHOD: 256 parents of children ages 0-6 completed an online survey about sunscreen use, newborn Vitamin K injections, influenza vaccination, routine vaccination, car seats, infant safe sleep, furniture anchoring, large trampoline use, and firearm safety. Multivariable models regressed: 1) communication about each guideline on parents' corresponding guideline adherence; 2) trust, comfort discussing guidelines, agreement with guideline advice, self-efficacy, on parents' total guideline adherence. RESULTS: Communication about furniture anchoring (OR = 2.26), sunscreen (OR = 5.28), Vitamin K injections (OR = 3.20), influenza vaccination (OR = 13.71), routine vaccination (OR = 6.43), car seats (OR = 6.15), and infant safe sleep (OR = 3.40) related to corresponding guideline adherence (ps < 0.05). Firearm safety communication was not related to adherence (OR = 1.11, n.s.). Trampoline communication related to lower likelihood of trampoline guideline adherence (OR = 0.24, p = 0.001). Agreement with guideline advice (ß = 0.35), trust (ß = 0.34), self-efficacy (ß = 0.45), comfort discussing guidelines (ß = 0.35) positively related to total guideline adherence (ps < 0.001). CONCLUSION: Findings underscore the importance of provider communication about health/safety guidelines. PRACTICE IMPLICATIONS: Providers should respectfully engage and build relationships with parents to support health/safety guideline adherence.

Catalytic borylation of methane.

Despite steady progress in catalytic methods for the borylation of hydrocarbons, methane has not yet been subject to this transformation. Here we report the iridium-catalyzed borylation of methane using bis(pinacolborane) in cyclohexane solvent. Initially, trace amounts of borylated products were detected with phenanthroline-coordinated Ir complexes. A combination of experimental high-pressure and high-throughput screening, and computational mechanism discovery techniques helped to rationalize the foundation of the catalysis and identify improved phosphine-coordinated catalytic complexes. Optimized conditions of 150°C and 3500-kilopascal pressure led to yields as high as ~52%, turnover numbers of 100, and improved chemoselectivity for monoborylated versus diborylated methane.

Progesterone receptor isoforms A and B: temporal and spatial differences in expression during murine mammary gland development.

Progesterone is a potent mitogen in the mammary gland. Based on studies using cells and animals engineered to express progesterone receptor (PR) isoforms A or B, PRA and PRB are believed to have different functions. Using an immunohistochemical approach with antibodies specific for PRA only or PRB only, we show that PRA and PRB expression in mammary epithelial cells is temporally and spatially separated during normal mammary gland development in the BALB/c mouse. In the virgin mammary gland when ductal development is active, the only PR protein isoform expressed was PRA. PRA levels were significantly lower during pregnancy, suggesting a minor role at this stage of development. PRB was abundantly expressed only during pregnancy, during alveologenesis. PRA and PRB colocalization occurred in only a small percentage of cells. During pregnancy there was extensive colocalization of PRB with 5-bromo-2'-deoxyuridine (BrdU) and cyclin D1; 95% of BrdU-positive cells and 83% of cyclin D1-positive cells expressed PRB. No colocalization of PRA with either BrdU or cyclin D1 was observed at pregnancy. In the virgin gland, PRA colocalization with BrdU or cyclin D1 was low; only 27% of BrdU-positive cells and 4% of cyclin D1-positive cells expressed PRA. The implication of these findings is that different actions of progesterone are mediated in PRB positive vs. PRA-positive cells in vivo. The spatial and temporal separation of PR isoform expression in mouse mammary gland provides a unique opportunity to determine the specific functions of PRA vs. PRB in vivo.

Estrogen mediates mammary epithelial cell proliferation in serum-free culture indirectly via mammary stroma-derived hepatocyte growth factor.

Epithelial-stromal cell interactions are important for normal development and function of the mouse mammary gland. The steroid hormone estrogen is required for epithelial cell proliferation and ductal development in vivo. Recent studies of estrogen receptor alpha knockout mice indicate that estrogen-induced proliferation is dependent upon the presence of estrogen receptor in mammary stromal cells, but not in epithelial cells. The purpose of the present study was to identify the underlying mechanism of estrogen-dependent stroma-derived effects on mammary epithelium. We have developed a minimally supplemented serum-free medium, collagen gel primary mammary coculture system to address the issue of stroma-derived, estrogen-dependent effects on epithelial cell proliferation. Conditioned medium from mammary fibroblasts or coculture with mammary fibroblasts caused increased epithelial cell proliferation and produced tubular/ductal morphology. Hepatocyte growth factor (HGF) was identified as the mediator of this effect, as the proliferative activity in fibroblast-conditioned medium was completely abolished by neutralizing antibody to HGF, whereas neutralizing antibodies to either epidermal growth factor or IGF-I had no effect. Treatment of mammary fibroblasts with estrogen increased the production of HGF. From these results we conclude that estrogen may indirectly mediate mammary epithelial cell proliferation via the regulation of HGF in mammary stromal cells and that HGF plays a crucial role in estrogen-induced proliferation in vivo.