Tetrahedral Keggin Core Tunes the Visible Light-Assisted Catalase-Like Activity of Icosahedral Keplerate Shell.

In this work, the effect of Keggin polyoxometalates encapsulated in Keplerate {Mo72Fe30} shell (K shell) on the visible light-assisted catalase-like activity (H2O2 dismutation) of the resulting core-shell clusters PMo12@K, SiMo12@K, and BW12@K was investigated. Superior photodismutation activity of PMo12@K compared to that of K shell and two other core-shell clusters was discovered. The homogeneity of PMo12@K and its improved oxidative stability, increased redox potential, and reduced band gap caused by a synergistic effect between the Keplerate shell and Keggin core seem reasonable to explain such a superiority. The light-dependent photocatalytic performance of PMo12@K evaluated by action spectra revealed a maximum apparent quantum efficiency (AQY) at 400 nm, demonstrating the visible light-driven photocatalytic reaction. A first-order rate constant of 2 × 10-4 s-1 and activation energy of 108.8 kJ mol-1 alongside a turnover frequency of 0.036 s-1 and a total turnover number of up to ∼3800 approved the effective photocatalytic activity and improved the oxidative stability of PMo12@K. A nonradical photocatalytic mechanism through a Fe-OOH intermediate was proposed. Thus, the structure, optical activity, and oxidative stability of a host Keplerate-type nanocluster can be tuned significantly by encapsulation of a guest, like "cluster-in-cluster" structures, which opens the scope for introducing new visible light-sensitive hierarchical nanostructures.

Construction of ZIF-67-On-UiO-66 Catalysts as a Platform for Efficient Overall Water Splitting.

A well-organized construction of hybrid metal-organic frameworks (MOFs) with exquisite structures is vital due to their potential applications. Herein, a novel hybrid nanostructure of UiO-66-on-ZIF-67, denoted as MZU-CoxZry (x and y represent the mass ratios of ZIF-67 and UiO-66, respectively), was successfully prepared by a simple method and showed a highly efficient and stable bifunctionality of both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in an alkaline medium. The MZU-Co2.5Zr1 shows remarkable OER performance with a low overpotential of 252 mV and an overpotential of 172 mV @ 10 mA/cm2 for HER in 1 mol/L KOH. With MZU-Co2.5Zr1 as the cathode and anode, the integrated water decomposition device has achieved low total potentials of 1.56 V @ 10 mA/cm2 and 1.59 V @ 30 mA/cm2, exhibiting its excellent performance of overall water splitting. Based on the experimental results, the mechanism of the superior electrocatalytic performance of MZU-CoxZry was discussed. This work supplies guidance for the rational design of non-precious composites for energy conversion.

Tandem Photocatalysis Protocol for Hydrogen Generation/Olefin Hydrogenation Using Pd-g-C3N4-Imine/TiO2 Nanoparticles.

An unprecedented visible-light-driven photocatalytic system consisting of Pd nanoparticles stabilized on g-C3N4-imine-functionalized TiO2 nanoparticles was discovered for photoassisted hydrogen generation followed by olefin hydrogenation under mild conditions. The structural integrity of the as-synthesized photocatalyst was corroborated by Fourier transform infrared spectroscopy, X-ray powder diffraction, energy-dispersive X-ray spectroscopy, inductively coupled plasma atomic emission spectroscopy, X-ray photoelectron spectroscopy, ultraviolet-diffuse reflectance spectroscopy, Brunauer-Emmett-Teller measurements, and thermogravimetric analysis (TGA). Transmission electron microscopy and high-resolution scanning electron microscopy revealed the nanoscopic nature of the catalyst. The photocatalyst promoted several different transformations in a one-pot reaction sequence: hydrogen evolution through photocatalytic acceptorless formation of benzimidazoles as important therapeutic agents followed by visible-light-driven photocatalytic reduction of olefins with a high hydrogen utilization efficiency of up to 92% under mild conditions. A significant volume of H2 was produced under blue light-emitting diode (LED) irradiation during the selective formation of benzimidazole, while the selectivity reduced significantly under a Xe lamp or in the dark. The in situ-generated H2 could be activated by the as-prepared Pd-C3N4-imine/TiO2 photocatalyst to effectively hydrogenate olefins under mild conditions at appropriate time exposed to blue LED irradiation. The light-dependent photocatalytic performance of the title catalyst was assessed using action spectra by calculating the apparent quantum efficiency (AQE), which exhibited the maximum AQEs at 410 and 550 nm, at which the highest performance for styrene hydrogenation was obtained. The improved photoredox activity of the title nanohybrid could be caused by the synergistic effects of the heterojunction of carbon nitride-Pd on TiO2 nanoparticles evidenced by photoluminescence spectra and catalytic reactions. The catalyst proved to be air-stable, robust, recyclable, and very active in the absence of any undesirable additives and reducing agents. Thus, this work presents a new protocol for improving the photocatalytic properties of semiconducting materials for various photocatalytic applications under environmentally friendly conditions.

Vitamin B5 copper conjugated triazine dendrimer improved the visible-light photocatalytic activity of TiO2 nanoparticles for aerobic homocoupling reactions.

In this work, Cu-vitamin B5 (pantothenic acid) bonded to 2,4,6-trichloro-1,3,5-triazine produced a bioconjugated dendrimer giving rise to the visible-light photocatalytic activity of nanocrystalline TiO2. XPS spectra uncovered the coexistence of Cu(II)/Cu(I) oxidation states with a predominant contribution of Cu(I). The new heterogeneous bio-relevant Cu-photocatalyst (Cu(I) Cu(II) [PTAPA G2-B5] @TiO2) revealed a band gap value [Eg = (2.8 eV)] less than those of Cu free components [PTAPA G1-B5]@TiO2 (3.04) and [PTAPA G2-B5]@TiO2 (3.06) and particularly the bare TiO2 (3.15 eV). The reactions showed to be light-dependent with the best performance under room light bulbs. The photocatalytic efficiency of the as-prepared heterojunction photocatalyst was exploited in the aerobic Csp2-Csp2 homocoupling of phenylboronic acid and Csp-Csp homocoupling of phenyl acetylenes under visible-light irradiation to prepare structurally and electronically different biaryls. A radical pathway relying on the photogenerated e- and h+ and involving the Cu(I)-Cu(II) synergistic cooperation was postulated. The reusability and stability of the catalyst were verified by the recycling test, FT-IR spectra, and ICP-OES analysis.

Catalytic epoxidation activity of keplerate polyoxomolybdate nanoball toward aqueous suspension of olefins under mild aerobic conditions.

Catalytic efficiency of a sphere-shaped nanosized polyoxomolybdate {Mo132} in the aerobic epoxidation of olefins in water at ambient temperature and pressure in the absence of reducing agent is exploited which resulted good-to-high yields and desired selectivity.

Enhanced Visible-Light-Induced Photocatalytic Activity in M(III)Salophen-Decorated TiO2 Nanoparticles for Heterogeneous Degradation of Organic Dyes.

In this work, the construction of two heterojunction photocatalysts by coordinative anchoring of M(salophen)Cl complexes (M = Fe(III) and Mn(III)) to rutile TiO2 through a silica-aminopyridine linker (SAPy) promotes the visible-light-assisted photodegradation of organic dyes. The degradation efficiency of both cationic rhodamine B (RhB) and anionic methyl orange (MO) dyes by Fe- and Mn-TiO2-based catalysts in the presence of H2O2 under sunlight and low-wattage visible bulbs (12-18 W) is investigated. Anionic MO is more degradable than cationic RhB, and the Mn catalyst shows more activity than its Fe counterpart. Action spectra demonstrate the maximum apparent quantum efficiency (AQY) at 400-450 nm, confirming the visible-light-driven photocatalytic reaction. The enhanced photocatalytic activity might be attributed to the improved charge transfer in the heterojunction photocatalysts evidenced by photoluminescence (PL) and electrochemical impedance spectroscopy (EIS) analyses. A radical pathway for the photodegradation of dyes is postulated based on scavenging experiments and spectral data. This work provides new opportunities for constructing highly efficient catalysts for wastewater treatment.

Cu(ii)-vitamin C-complex catalyzed photo-induced homocoupling reaction of aryl boronic acid in base-free and visible light conditions.

In this work, the photocatalytic efficiency of Cu(ii)-vitamin C complex immobilized on titanium dioxide nanoparticles was exploited in the photo-assisted homocoupling reaction of aryl boronic acids under heterogeneous conditions. The homocoupling reaction affords the corresponding symmetrical biaryls in 50-97% yields at ambient temperature in the air under visible light irradiation without any need for any additive such as base or oxidant. This method tolerates various substituents on the aryl boronic acids such as halogen, carbonyl, and a nitro group. The light-dependent photocatalytic performance of the title catalyst evaluated by action spectra revealed a maximum apparent quantum efficiency (AQYs) at 410 nm demonstrating the visible-light-driven photocatalytic reaction. The as-prepared nano biophotocatalyst proved to be reusable at least six times without losing its activity. Thus this work exhibits a favorable method from the environmental and economic point of view which enables the industrially important reactions such as coupling reactions, to be carried out efficiently under photocatalytic and practically attainable conditions.

TiO2 nanoparticles decorated with Co-Schiff base-g-C3N4 as an efficient photocatalyst for one-pot visible light-assisted synthesis of benzimidazoles.

In this study, a novel heterogeneous visible light-driven nanocatalyst was produced via the complexation of Co(ii) with g-C3N4-imine-functionalized TiO2 nanoparticles. It was characterized using different techniques such as Fourier-transform infrared (FT-IR), energy-dispersive X-ray spectrum (EDS), inductively coupled plasma atomic emission spectroscopy (ICP-AES), thermogravimetric analysis (TGA), ultraviolet-visible diffuse reflectance spectroscopy (UV-vis DRS), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The catalyst promoted several different transformations in a one-pot reaction sequence: aerobic photooxidation of benzylic alcohols to aldehydes and then the tandem synthesis of benzimidazoles through the dehydrogenative coupling of primary benzylic alcohols and aromatic diamines. The photocatalyst proved to be highly active, robust, selective, and recyclable under organic reaction conditions and provided affordable products with good to high yields. The results proposed that the improved photoactivity predominantly benefits from the synergistic effects of the heterojunction of Co-carbon nitride on TiO2 nanoparticles. Moreover, this protocol provides standard conditions avoiding undesirable additives and limitations of oxidation methods, and may help to develop a new strategy for the development of photocatalysis based organic transformations.

A top-down design for easy gram scale synthesis of melem nano rectangular prisms with improved surface area.

An unprecedented top-down design for the preparation of melem by 1 h stirring of melamine-based g-C3N4 in 80 °C concentrated sulfuric acid (95-98%) was discovered. The melem product was formed selectively as a monomer on the gram scale without the need for controlled conditions, inert atmosphere, and a special purification technique. The as-prepared air-stable melem showed a distinctive nano rectangular prism morphology that possesses a larger surface area than the melems achieved by traditional bottom-up designs making it a promising candidate for catalysis and adsorption processes.

The enhanced visible-light-induced photocatalytic activities of bimetallic Mn-Fe MOFs for the highly efficient reductive removal of Cr(vi).

The photocatalytic efficiencies of bimetallic MOFs, namely STA-12-Mn-Fe, for the reductive removal of Cr(vi) were explored. The best effective variable values were obtained and correlation between the response and influential variables was optimized via experimental design methodology. Complete Cr(vi) removal was achieved under natural sunlight and fluorescent 40 W lamp radiation at pH 2, with an initial Cr(vi) concentration of 20 mg L-1, and 10 mg of photocatalyst within 30 min. A pseudo-first-order rate constant of 0.132 min-1 at T = 298 K was obtained for the Cr(vi) reduction reaction. The title catalysts revealed high performance in the visible region based on photoefficiency measurements, while improved activity was observed compared to the corresponding single-metal MOFs under natural sunlight, highlighting the synergistic effect between the two metal ions. Trapping experiment results proved that direct electron transfer is the main pathway during the photocatalytic Cr(vi) reduction process.

Cu(ii) vitamin C tunes photocatalytic activity of TiO2 nanoparticles for visible light-driven aerobic oxidation of benzylic alcohols.

The incorporation of Cu(OAc)2 into ascorbic acid coated TiO2 nanoparticles easily provided a new heterogeneous visible-light active titania-based photocatalyst (TiO2-AA-Cu(ii)) which was characterized by different techniques such as FT-IR, XPS, ICP-AES, TGA and TEM. A red-shift of the band-edge and a reduction of the band-gap (2.8 eV vs. 3.08 for TiO2) were demonstrated by UV-DRS and Tauc plots. The combination of the as-prepared TiO2-AA-Cu(ii) nanoparticles with TEMPO and molecular oxygen (air) afforded an active catalytic system for the selective oxidation of diverse set of benzylic alcohols under solvent-free conditions. A photoassisted pathway was confirmed for oxidation reactions evidenced by good correlation between apparent quantum yield (AQY) and diffuse reflectance spectra (DRS) of the as-prepared nanohybrid. The spectral data and recycling experiments demonstrated the structural stability of the title copper photocatalyst during oxidation reactions.

Heterogeneous Fenton-like activity of novel metallosalophen magnetic nanocomposites: significant anchoring group effect.

Two new pyridine and thiolate anchoring groups were prepared to functionalize γ-Fe2O3 nanoparticles for coordinative attachment of simple Fe(iii)- and Mn(iii)salophen complexes. Four new magnetically recoverable composites were characterized by several analytical techniques such as FT-IR, XRD, TGA, EDS compositional analysis and VSM to confirm superparamagnetic properties. TEM images revealed the nanostructure nature of composites with size ranging between 20 and 40 nm. A heterogeneous advanced oxidation process for degradation of some organic dyes as water pollution compounds using an aqueous solution of H2O2 were successfully exploited. Several key parameters including the metal center in the salophen complex, initial pH, catalyst dosage, H2O2 and dye concentration and temperature were investigated. A significant effect of the anchoring ligand on the degradation efficiency and catalyst stability was documented. The superior catalytic activity and particularly durability of the thiolate-based catalysts were demonstrated in comparison with their Py counterparts. Rate constants of 0.21, 0.17, 0.23 and 0.11 min-1 were obtained for degradation of rhodamine B (RhB), methylene blue (MB), methyl orange (MO), and crystal violet (CV). Finally, a photoluminescence probing technology and radical scavenging measurements were carried out to elucidate the active species involved in the process.

A nanoscopic icosahedral {Mo72Fe30} cluster catalyzes the aerobic synthesis of benzimidazoles.

In this study, the catalytic efficiency of amorphous {Mo72Fe30} nanocapsules as a safe Keplerate polyoxometalate in organic synthesis was exploited. The easy-made solid catalyst exhibited high efficiency using a very low dosage (0.02-0.05 mol%) in the catalyzed condensation of various aromatic 1,2-diamines and aldehydes for the aerobic synthesis of benzimidazoles with very small E-factor values (0.11-0.33). The superior catalytic activity of amorphous nanoclusters compared to that of its crystalline counterpart was demonstrated. The high activity and recyclability of heterogeneous catalysts in a green reaction media under oxygen atmosphere, make this environmentally benign organic process appropriate for our applied goals.

A Cooperative Effect in a Novel Bimetallic Mo-V Nanocomplex Catalyzed Selective Aerobic C-H Oxidation.

In this study, a new heterobimetallic Mo(VI)-V(V) organosilicon Schiff base complex has been prepared and characterized by different techniques, such as FTIR, Raman, MS, ICP-AES, TGA, and XPS. The bimetallic nanocomplex, revealed by TEM images, showed high oxidation stability and desired activity in the aerobic oxidation of a structurally diverse set of benzylic alcohols in ethanol as a safe solvent. Further, oxidation of benzylic hydrocarbons successfully occurred, producing the target compounds in high yields and excellent selectivities. Our results demonstrated a cooperative effect between Mo(VI) and V(V) as redox active sites in an organosilicon Schiff base framework. A facile and practical reusability of the solid catalyst at the end of the reaction was observed.

Screening of different interactions in oxo-manganese porphyrin dimers containing axial N-donor ligands: a theoretical study.

A theoretical analysis for describing the dimeric assemblies of high-valent manganese(v)-oxo meso-tetraphenylporphyrin (TPP) ([(TPP)MnVO]2 2+) and meso-tetrakis(pentafluorophenyl)porphyrin (TPFPP) ([(TPFPP)MnVO]2 2+) in the presence of axial N-donor ligands is presented. Our theoretical results revealed two types interactions in dimers: a sandwich-like interaction between phenyl rings of porphyrin molecules, and a non-bonded T-shape interaction between nitrogen donors attached to Mn centers. The curvature in the geometry of porphyrin in the [(TPP)MnVO]2 2+/N-donor system is significantly smaller than that of [(TPFPP)MnVO]2 2+/N-donor system. Moreover, the Mn-N(ax) distances in [(TPFPP)MnVO]2 2+/N-donor system are shorter than those of [(TPP)MnVO]2 2+/N-donor system. Also, the donor-acceptor interaction between the imidazoles and the Mn centers are stronger than those of the other ligands in both porphyrins. These results are supported by atoms in molecules (AIM) and natural bond orbital (NBO) analysis.

Causal Effect of Donor Source on Survival of Renal Transplantation Using Marginal Structural Models.

BACKGROUND: Marginal Structural Models (MSMs) are novel methods to estimate causal effect in epidemiology by using Inverse Probability of Treatment Weighting (IPTW) and Stabilized Weight to reduce confounding effects. This study aimed to estimate causal effect of donor source on renal transplantation survival. METHODS: In this cohort study, 1354 transplanted patients with a median 42.55 months follow-up in Namazee Hospital Transplantation Center, Shiraz from Mar 1999 to Mar 2009, were included to use marginal structural Cox regression, binomial logistic regression model to estimate causal effect of donor source on the survival of renal transplantation. IPTW and stabilized inverse probability of treatment weighting are used as weights. RESULTS: The un-weighted (crude) hazard ratios for live unrelated donor and deceased donor in comparison to live related donor as reference group was (HR: 1.03, 95% CI: 0.58-1.83, P=0.89) and (HR: 2.69, 95% CI: 1.67-4.31, P=0.001), respectively. Using a marginal structural Cox regression model and by stabilized weight, the hazard ratios for live-unrelated donor and cadaveric donor were (HR: 1.08, 95% CI: 0.47-2.45, P=0.84) and (HR: 3.63, 95% CI: 1.59-8.26, P=0.002), respectively. There was no difference between estimated effect size from marginal structural Cox regression, marginal structural logistic regression, and marginal structural Weibull regression model. CONCLUSION: There is no difference between related and unrelated donor source hazard ratio; however, hazard ratio for cadaveric donor was 3.63 times of hazard ratio for related donor and 3.34 times of it for unrelated donor. Therefore, the live donor (related or unrelated) has a better survival of renal transplantation than cadaveric donor.

A new and highly selective turn-on fluorescent sensor with fast response time for the monitoring of cadmium ions in cosmetic, and health product samples.

Cadmium (Cd) which is an extremely toxic could be found in many products like plastics, fossil fuel combustion, cosmetics, water resources, and wastewaters. It is capable of causing serious environmental and health problems such as lung, prostate, renal cancers and the other disorders. So, the development of a sensor to continually monitor cadmium is considerably demanding. Tetrakis(4-nitrophenyl)porphyrin, T(4-NO2-P)P, was synthesized and used as a new and highly selective fluorescent probe for monitoring cadmium ions in the "turn-on" mode. There was a linear relationship between fluorescence intensity and the concentration of Cd(II) in the range of 1.0×10(-6) to 1.0×10(-5)molL(-1) with a detection limit of 0.276µM. To examine the most important parameters involved and their interactions in the sensor optimization procedure, a four-factor central composite design (CCD) combined with response surface modeling (RSM) was implemented. The practical applicability of the developed sensor was investigated using real cosmetic, and personal care samples.

Development of a new chemically modified carbon paste electrode for selective determination of urinary and serum oxalate concentration.

The construction and evaluation of a novel modified carbon paste electrode with high selectivity toward oxalate ion are described. The constructed carbon paste potentiometric sensor for oxalate ion is based on the use of a zirconium salan complex as a good ionophore in the carbon paste matrix. The electrode exhibits a Nernstian slope of 29.1 mV/decade to oxalate ion over a wide concentration range from 1.5×10(-6) to 3.9 ×10(-2) mol L(-1) with a low detection limit of 7.0×10(-7) mol L(-1). The electrode possesses fast response time, satisfactory reproducibility, appropriate lifetime, and most importantly, good selectivity toward C2O4(2-) relative to a variety of common anions. The potentiometric response of the electrode is independent of the pH of the test solution in the pH range 2.5-8.0. The modified carbon paste electrode was successfully applied as an indicator electrode in potentiometric titration and potentiometric determination of oxalate ion in mineral water, blood serum and urine samples.

Cytochrome P-450 model reactions: efficient and highly selective oxidation of alcohols with tetrabutylammonium peroxymonosulfate catalyzed by Mn-porphyrins.

A novel biomimetic method for rapid oxidation of a wide range of benzylic, allylic, aliphatic, primary and secondary alcohols to the related aldehydes and ketones using Bu(4)NHSO(5) catalyzed by Mn(TPP)OAc/pyridine system with high to excellent yields and excellent selectivity has been developed. The high turnover rates obtained in this catalytic system represent a high efficiency and also relative stability of Mn-porphyrin catalyst towards oxidative degradation. The presence of an electron-withdrawing group on the phenyl ring of both benzyl alcohol and porphyrin ligand increases the reactivity of substrate as well as catalytic activity of Mn-porphyrin catalyst in the oxidation reaction.