Alkaline earth metal (Mg, Sr, Ba)-organic frameworks based on 2,2',6,6'-tetracarboxybiphenyl for proton conduction.

Three new alkaline earth metal based metal-organic frameworks (MOFs), namely M-BPTC (M = Mg, Sr, Ba), have been synthesized by using BPTC (2,2',6,6'-tetracarboxybiphenyl) as ligand under hydrothermal conditions. These MOFs exhibit interesting structural diversity, variable chemical and thermal stability, as well as proton conductivity. Mg-BPTC with the formula {[Mg(BPTC)0.5(H2O)3]·5H2O}n consists of BPTC(4-) extended metal layers, and novel highly ordered infinite tape-like structures of cyclic water octamers reside interlayer. Three-dimensional porous {[Sr2(BPTC)(H2O)6]·H2O}n (Sr-BPTC) features inorganic Sr-O chains (I(1)O(2)) and open hydrophilic channels where water heptamers and carboxyl oxygen atoms conspire to form H-bond networks, whereas 3D {[Ba6(BPTC)3(H2O)6]·11H2O}n (Ba-BPTC) shows Ba-O inorganic layer (I(2)O(1)) and 1D channels incorporating large water 14-mers and 18-mers. M-BPTC (M = Mg, Sr) species exhibit excellent water stability and proton conductivity due to their respective appropriate pathways for proton transporting. M-BPTC (M = Sr, Ba) structures are highly thermally stable due to the presence of the inorganic connectivity. The present results suggest that M-BPTC (M = Mg, Sr) are promising materials for proton conduction and provide insight into the hydrogen bonding motif.

Self-assembly of an imidazolate-bridged Fe(III)/Cu(II) heterometallic cage.

A rare, discrete, mixed-valent, heterometallic Fe(III)/Cu(II) cage, [Cu6Fe8L8](ClO4)12·χsolvent (H3L = tris{[2-{(imidazole-4-yl)methylidene}amino]ethyl}amine), was designed and synthesized via metal-ion-directed self-assembly with neutral tripodal metalloligands. The formation of this coordination cage was demonstrated by X-ray crystallography, ESI mass spectrometry, FT-IR, and UV-vis-NIR spectroscopy.

Au25 Nanoclusters Incorporating Three-Dimensionally Ordered Macroporous In2O3 for Highly Sensitive and Selective Formaldehyde Sensing.

Detection of formaldehyde (FA) in the atmosphere is of significant importance because exposure to FA may cause serious health problems such as sick-house syndrome, leukemia, and cancer. Modifying metal oxide semiconductors (MOSs) with noble metal nanoparticles (NPs) is an efficient method to enhance FA-sensing properties. Herein, a series of Au25 nanocluster (NC)-decorated three-dimensionally ordered macroporous In2O3 materials (Au25/3DOM In2O3) is created, and the loading amount of Au25 NCs was optimized based on FA responses. To reveal the effect of gold size on FA responses, we constructed Au144 NC-loaded 3DOM In2O3 and Au NP (2.9 nm)-modified 3DOM In2O3 and compared their gas-sensing properties with the optimal Au25/3DOM In2O3. The results show that in comparison with its counterparts, the optimal Au25/3DOM In2O3 presents higher sensitivity, shorter response/recovery times, better selectivity, and excellent reproducibility. More attractively, the responses to FA are dependent on the size of Au particles loaded on In2O3. We suggest that the enhanced FA responses for the optimal material are mainly attributed to the electronic and chemical-sensitization effects of Au25 NCs, and the size-dependent effect of FA responses is ascribed to the size of Au NPs affecting the formation of oxygen-adsorbing species. This work provides an efficient way for fabricating noble metal NP-loaded MOSs with tunable gas-sensing properties.

Construction of organic-inorganic "chelate" adsorption sites on metal oxide semiconductor for room temperature NO2 sensing.

Metal oxide semiconductors (MOS) have been extensively studied for gas sensing due to their excellent chemical stability and adjustable electronic properties. However, there is still a lack of ingenious design strategies to achieve customizable gas detection in complex environments. Herein, a novel and scalable strategy of constructing organic-inorganic "chelate" adsorption sites is proposed to promote the affinity of MOS sensing materials to target molecules. Specifically, 3-aminopropyltriethoxysilane (APTES)-functionalized reduced graphene oxide (rGO) was decorated on In2O3 tubes (AG/Inx), and its NO2 sensing performance was studied. As a result, the optimal AG/Inx shows boosted room-temperature NO2 response, and its response to 1 ppm NO2 is 4.8 times that of In2O3. More attractively, the optimal AG/Inx exhibits good selectivity, as well as outstanding detection ability (Rg/Ra = 1.6) for low concentration NO2 (20 ppb). Experimental results suggest that APTES-rGO not only acts as the electron acceptor to accelerate charge transfer, but also enhances NO2 adsorption. Further theoretical calculations reveal that NO2 is simultaneously adsorbed at rGO and APTES via a flexible "chelate" mechanism. The multidentate adsorption configuration remarkably strengthens the NO2-host interaction, which is conducive to improving sensing performance. This work may inspire the material design of a new generation high-performance gas sensors.

Selective Photocatalytic Reduction of CO2 to CH4 Modulated by Chloride Modification on Bi2WO6 Nanosheets.

Solar-driven photocatalytic CO2 reduction into CH4 with H2O is considered to be a promising way to alleviate the energy crisis and greenhouse effect. However, current CO2 photoreduction technologies tend to overlook the role of photooxidation half reaction as well as the effect of the protons produced by water oxidation on CH4 generation, resulting in low CO2 conversion efficiency and poor CH4 selectivity. In the present study, a series of chloride-modified Bi2WO6 nanosheets were constructed in view of chloride-assisted photocatalytic water oxidation. The results show that the CH4 yield of the synthesized sample can be enhanced up to about 10 times compared to that with no Cl- modification. Besides, the selectivity of CH4 can be regulated by the loading amount of chloride, varying from 51.29% for Bi2WO6 to 94.98% for the maximum. The increase of product yield is attributed to chloride modification, which not only changed the morphology of the catalyst, but also modified the pathway of water oxidation. Further studies on intermediate products and the density functional theory calculation confirm that the Cl- ions on Bi2WO6 nanosheets not only promote H2O oxidation, but also lower the energy barrier for intermediate *CHO generation, thus facilitating CH4 production. The results gained herein may provide some illuminating insights into the design of a highly selective photocatalyst for efficient CO2 reduction.

N-Doped Graphene Quantum Dot-Decorated Three-Dimensional Ordered Macroporous In2O3 for NO2 Sensing at Low Temperatures.

Nitrogen dioxide (NO2) detection is of great importance because the emission of NO2 gas profoundly endangers the natural environment and human health. However, a few challenges, including lowering detection limit, improving response/recovery kinetics, and reducing working temperature, should be further addressed before practical applications. Herein, a series of N-doped graphene quantum dot (N-GQD)-modified three-dimensional ordered macroporous (3DOM) In2O3 composites are constructed and their NO2 response properties are studied. The results show that compared to pure 3DOM In2O3, reduced graphene oxide (rGO)/3DOM In2O3, and N-doped graphene sheets (NS)/3DOM In2O3, the N-GQDs/3DOM In2O3 sensing materials exhibit higher NO2 responses with fast response and recovery speed and low working temperature (100 °C). In addition, the detection limit of NO2 response for the optimal N-GQDs/In2O3 sensor is as low as 100 ppb. Upon exposure to CO, CH4, NH3, acetone, ethanol, toluene, and formaldehyde, only very weak responses could be observed, indicating good selectivity for the synthesized material. More attractively, the responses of the optimized N-GQDs/In2O3 sensor exhibit no obviously big fluctuation over 60 days, implying good long-term stability. We suggest that the formation of heterojunctions between 3DOM In2O3 and N-GQDs and the doping N atoms in N-GQDs play crucial roles in improving the NO2 sensing properties.

Co nanoparticles supported on three-dimensionally N-doped holey graphene aerogels for electrocatalytic oxygen reduction.

The reactive and stable catalysts for the oxygen reduction reaction are highly desirable for low temperature fuel cells. The commercial oxygen reduction reaction electrocatalysts generally reply on noble metal based nanomaterials, which suffer from inherent cost and selectivity issues. At present, it still remains challenge for designing efficient non-noble metal-based oxygen reduction reaction electrocatalysts. Herein, we successfully synthesize Co nanoparticles supported on three-dimensionally N-doped holey graphene aerogels hybrids by the high-temperature calcination of the graphene aerogels-polyallylamine-CoII hybrids. The component optimized hybrids show the excellent electrocatalytic activity for oxygen reduction reaction in alkaline media, which is comparable to commercial Pt/C electrocatalyst. Meanwhile, the hybrids also show eminent tolerance for CO and methanol, attributing to their excellent oxygen reduction reaction selectivity. The three-dimensionally interconnected structure of graphene aerogels, N-doping, uniform dispersion and high crystallinity of Co nanoparticles, and holey structure of graphene contribute to the striking oxygen reduction reaction activity of hybrids.

Rapid oxidation-etching synthesis of low-crystalline δ-MnO2 tubular nanostructures under ambient with high capacitance.

The 1D low-crystalline and ultrathin MnO2-RT nanotubes consisted of tiny nanoflakes are rapid synthesized at ambient temperature through a facile oxidation-etching method, where Cu nanowires are served as sacrificial templates. Meanwhile, the MnO2-RT nanotubes can be undergone further nucleation and growth to generate 3D porous MnO2 nanotubes by calcination treatment and hydrothermal reaction, respectively. Importantly, the high specific capacitance of 384.6 F g-1 is obtained at the current density of 0.25 A g-1 for the low-crystalline MnO2-RT nanotubes, owing to its ultra-thin wall thickness, high surface area and highly disordered structure. Furthermore, the cycle stability of the low-crystalline MnO2 nanotubes can be improved by hydrothermal treatment, owing to the enhanced crystallinity.

Self-template synthesis of defect-rich NiO nanotubes as efficient electrocatalysts for methanol oxidation reaction.

Developing robust and inexpensive non-noble metal based anode electrocatalysts is highly desirable for alkaline direct methanol fuel cells (ADMFCs). Herein, we successfully develop a facile self-template synthetic strategy for gram-grade porous NiO nanotubes (NTs) by pyrolyzing a nanorod-like Ni-dimethylglyoxime complex. The pyrolysis temperature highly correlates with the morphology and crystallinity of NiO NTs. The optimal NiO NTs exhibit a large electrochemically active surface area, a fast catalytic kinetics, and a small charge transfer resistance, which induce an outstanding electrocatalytic activity for the methanol oxidation reaction (MOR). Compared with conventional NiO nanoparticles, NiO NTs achieve a 11.5-fold increase in mass activity at 1.5 V for the MOR due to nanotubal morphology and abundant non-vacancy defects on the NiO NT surface. Moreover, NiO NTs have a higher electrocatalytic activity for the intermediates of the MOR (such as formaldehyde and formate) than conventional NiO nanoparticles, which also contribute to MOR activity enhancement. Given the facile synthesis and enhanced electrocatalytic performance, NiO NTs may be promising anode electrocatalysts for ADMFCs.

Carbonate doped Bi2MoO6 hierarchical nanostructure with enhanced transformation of active radicals for efficient photocatalytic removal of NO.

Doping heteroatoms in photocatalyst is an effective strategy to signally enhance the photocatalytic activity. Herein, we have favorably fabricated the carbonate doped Bi2MoO6 via a facile one-pot solvothermal method, which was verified by structure and constituent characterization analysis. In addition, the NO removal efficiency of carbonate-intercalated Bi2MoO6 is ~34%, far-exceeding that of the pure Bi2MoO6 (~13%), whilst exhibits a good stability and durability, owing to that the dopants could modulate the electron states of the Bi2MoO6, thus stimulating charge separation and migration, incenting transformation of reactive oxygen species and facilitating reactants activation, which are synthetically investigated by experimental characterization coupled with DFT calculation. Significantly, the in situ DRIFTS measurement was employed to dynamic monitor the NO oxidation process and clarify the photocatalytic mechanism under visible light irradiation. This work provides an efficient strategy to design photocatalysts with tunable motivating charge conversion and reactants activation towards NO photooxidation.

One-step hydrothermal synthesis of Cu-doped MnO2 coated diatomite for degradation of methylene blue in Fenton-like system.

In this work, we have synthesized Cu-doped MnO2@diatomite successfully though a one-step hydrothermal approach. Meanwhile, application for degradation of methylene blue in Fenton-like system was investigated. The compounds were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscope (XPS), Inductively Coupled Plasma analysis (ICP) and UV-vis spectroscopy measurements, beam scanning electron microscope (FIB/SEM), energy dispersive X-ray spectrometer (EDS). The observations revealed that copper was indeed intercalated into layered structure of MnO2 and Density functional theory (DFT) calculations predicted that Cu2+ intercalated MnO2@diatomite brought about the narrowing of band gap and the enhancing of charge mobility during catalysis. Electron Density Difference of CuMnD demonstrated excellent oxidation ability to dissociate H2O2 and generate hydroxyl radical (OH) to degrade the MB. Moreover, the proper copper doping of sample is more easily to form oxygen defect, which generate more surface hydroxyl groups as reaction sites for surface adsorption. In addition, the degradation efficiency of CuMnD was tremendously influenced by the initial pH, H2O2 dosage and copper content of catalyst. Ultimately, 0.02-25-CuMnD along with molar ration of Cu/Mn with 0.4402 showed the best degradation efficiency which was about 96.2% within 4 h with 16.5 mM of H2O2 and pH 2.06.

Anion exchange of a cationic Cd(ii)-based metal-organic framework with potassium ferricyanide towards highly active Fe3C-containing Fe/N/C catalysts for oxygen reduction.

A highly active and stable Fe3C-containing Fe/N/C catalyst, derived from a cationic Cd(ii)-based metal-organic framework involving accurate control over Fe-doping via anion-exchange with potassium ferricyanide, shows superior oxygen reduction performance over the benchmark Pt/C catalyst in an alkaline electrolyte.

Cyanogel auto-reduction induced synthesis of PdCo nanocubes on carbon nanobowls: a highly active electrocatalyst for ethanol electrooxidation.

Direct ethanol fuel cells (DEFCs) with a high conversion efficiency are quite promising candidates for energy conversion devices. Herein, we have successfully synthesized PdCo alloy nanocubes supported on carbon nanobowl (denoted as Pd2Co1/CNB) nanohybrids by using the cyanogel auto-reduction method at high temperature. The morphology, composition and structure of Pd2Co1/CNB nanohybrids are characterized in detail, revealing that PdCo nanocubes have a high alloying degree and special {110} facets. In cyclic voltammetry measurements, Pd2Co1/CNB nanohybrids show a mass activity of 1089.0 A g Pd-1 and a specific activity of 40.03 mA cm-2 for ethanol electrooxidation at peak potential, which are much higher than that of the commercial Pd/C electrocatalyst (278.2 A gPd-1 and 8.22 mA cm-2). Additionally, chronoamperometry measurements show that Pd2Co1/CNB nanohybrids have excellent durability for ethanol electrooxidation. A high alloying degree, special {110} facets and the CNB supporting material contribute to the high activity and durability of Pd2Co1/CNB nanohybrids, making them a highly promising Pt-alternative electrocatalyst for ethanol electrooxidation in DEFCs.

Hexa-µ(2)-benzoato-bis-(2,2'-bipyrid-yl)trimanganese(II) monohydrate.

The complex molecule of the title compound, [Mn(3)(C(7)H(5)O(2))(6)(C(10)H(8)N(2))(2)]·H(2)O, contains a linear array of divalent manganese ions. The central Mn(II) atom, which is located on a crystallographic inversion center, is coordinated octa-hedrally by six benzoate O atoms. The two terminal Mn(II) ions are six-coordinated by four benzoate O atoms and two N atoms of 2,2'-bipyridyl. The central Mn(II) atom and the terminal Mn(II) ions are bridged by four benzoate ligands in a bidentate fashion, whereas the other two carboxyl-ate ligands form bridges through one O atom only and chelate the terminal Mn(II) atom. The mol-ecules pack together via van der Waals attractions and C-H⋯O hydrogen bonds.

An iron(III) phosphonate cluster containing a nonanuclear ring.

This communication reports the first example of cyclic ferric clusters with an odd number of iron atoms capped by phosphonate ligands, namely, [Fe9(mu-OH)(7)(mu-O)2(O3PC6H9)8(py)12]. The magnetic studies support a S = 1/2 ground state with an exchange coupling constant of about J approximately equal to -30 K.

Synergistic photocatalysis of Cr(VI) reduction and 4-Chlorophenol degradation over hydroxylated α-Fe2O3 under visible light irradiation.

A series of Fe2O3 materials with hydroxyl are synthesized in different monohydric alcohol (C2-C5) solvents by solvothermal method and characterized by XRD, BET, XPS, TG and EA. The amount of hydroxyl is demonstrated to be emerged on the surface of the as-synthesized Fe2O3 particles and their contents are determined to be from 7.99 to 3.74 wt%. The Cr(VI) reduction experiments show that the hydroxyl content of Fe2O3 samples exacts great influence on the photocatalytic activity under visible light irradiation (λ>400 nm) and that the Fe2O3 sample synthesized in n-butyl alcohol exhibits the optimal photocatalytic activity. The synergistic photocatalysis for 4-Chlorophenol (4-CP) degradation and Cr(VI) reduction over above Fe2O3 sample is further investigated. The photocatalytic ratio of Cr(VI) reduction are enhanced from 24.8% to 70.2% while that of 4-CP oxidation are increased from 13.5% to 47.8% after 1 h visible light irradiation. The Fe2O3 sample keeps good degradation rates of mixed pollutants after 9 runs. The active oxygen intermediates O2(-)˙, ˙OH and H2O2 formed in the photoreaction process are discovered by ESR measurement and UV-vis test. The photocatalytic degradation mechanism is proposed accordingly.

Indirect Z-Scheme BiOI/g-C3N4 Photocatalysts with Enhanced Photoreduction CO2 Activity under Visible Light Irradiation.

Rational design and construction of Z-scheme photocatalysts has received much attention in the field of CO2 reduction because of its great potential to solve the current energy and environmental crises. In this study, a series of Z-scheme BiOI/g-C3N4 photocatalysts are synthesized and their photocatalytic performance for CO2 reduction to produce CO, H2 and/or CH4 is evaluated under visible light irradiation (λ > 400 nm). The results show that the as-synthesized composites exhibit more highly efficient photocatalytic activity than pure g-C3N4 and BiOI and that the product yields change remarkably depending on the reaction conditions such as irradiation light wavelength. Emphasis is placed on identifying how the charge transfers across the heterojunctions and an indirect Z-scheme charge transfer mechanism is verified by detecting the intermediate I3(-) ions. The reaction mechanism is further proposed based on the detection of the intermediate (•)OH and H2O2. This work may be useful for rationally designing of new types of Z-scheme photocatalyst and provide some illuminating insights into the Z-scheme transfer mechanism.

Enhanced Photoreduction CO2 Activity over Direct Z-Scheme α-Fe2O3/Cu2O Heterostructures under Visible Light Irradiation.

Hematite-cuprous oxide (α-Fe2O3/Cu2O) nanocomposites are synthesized based on the design of Z-scheme photocatalyst for CO2 reduction. The band structure for the typical Fe2O3/Cu2O (with 1:1 mole ratio) is characterized by UV-vis reflectance spectroscopy and X-ray/ultraviolet photoelectron spectroscopy, and its heterojunction is determined to be Type II band alignment. The photoreduction CO2 activities of the heterostructures are investigated in the presence of water vapor. The CO yields are changed with Fe/Cu mole ratio, and the maximal CO yield attains 5.0 µmol·g cat(-1) after 3 h of visible-light irradiation. Besides the effect of light wavelength, H2O/CO2 molar ratio and temperature on the products is studied. The selectivity of the prepared catalysts is tunable by modulating the light wavelength. The reaction mechanism is proposed and further confirmed experimentally. The results gained herein may provide some insights into the design of Z-scheme photocatalysts for CO2 reduction.

Anion exchange induced tunable catalysis properties of an uncommon butterfly-like tetranuclear copper(II) cluster and magnetic characterization.

An uncommon butterfly-like tetranuclear copper(ii) cluster with the formula {[Cu(4)(µ(3)-OH)(2)(µ(4)-Cl)(H(2)O)(2)(L)(2)]·Cl(H(2)O)(7)}(n) (1) (H(2)L = 1,2-bis[3-(1,2,4-triazolyl)-4-amino-5-carboxylmethylthio]ethane) has been synthesized. Compound 1 exhibits interesting anion exchange characteristics, in which both guest and coordinated Cl(-) can be replaced by I(-) or NO(3)(-) in water. Furthermore, a high catalytic selectivity to produce poly(phenylene ether) by the oxidative coupling of 2,6-dimethylphenol in water is found to be 74% for 1 and 87% for the anion-exchanged product 1-MI(x), respectively. Additionally, the antiferromagnetic interaction among Cu ions for compound 1 is also found.

Dodecanuclear manganese(III) phosphonates with cage structures.

Treatments of Mn(O(2)CR)(2) (R = Me, Ph) with NBu(4)MnO(4) in CH(3)CN or CH(3)CN/CH(2)Cl(2) in the presence of acetic acid, delta(1)-cyclohexenephosphonic acid (C(6)H(9)PO(3)H(2)), and 2,2'-bipyridine or 1,10-phenanthroline result in three novel dodecamanganese(III) clusters [Mn(12)O(8)(O(2)CMe)(6)(O(3)PC(6)H(9))(7)(bipy)(3)] (1), [Mn(12)O(8)(O(2)CPh)(6)(O(3)PC(6)H(9))(7)(bipy)(3)] (2), and [Mn(12)O(8)(O(2)CPh)(6)(O(3)PC(6)H(9))(7)(phen)(3)] (3). They have a similar Mn(12) core of [Mn(III)(12)(mu(4)-O)(3)(mu(3)-O)(5)(mu-O(3)P)(3)] with a new type of topologic structure. Solid-state dc magnetic susceptibility measurements of complexes 1-3 reveal that dominant antiferromagnetic interactions are propagated between the magnetic centers. The ac magnetic measurements suggest an S = 2 ground state for compounds 1 and 3 and an S = 3 ground state for compound 2.