Applications of metal–organic frameworks for green energy and environment: New advances in adsorptive gas separation, storage and removal

The separation of gas molecules with similar physicochemical properties is of high importance but practically entails a substantial energy penalty in chemical industry. Meanwhile, clean energy gases such as H_2 and CH_4 are considered as promising candidates for the replacement of traditional fossil fuels. However, the technologies for the storage of these gases are still immature. In addition, the release of anthropogenic toxic gases into the atmosphere is a worldwide threat of growing concern. Both in academia and industry, considerable research efforts have been devoted to developing advanced porous materials for the effective and energy-efficient separation, storage, or capture of the related gases. In contrast to conventional inorganic porous materials such as zeolites and activated carbons, metal–organic frameworks(MOFs) are considered as a type of promising materials for gas separation and storage. In this contribution, we review the recent research advance of MOFs in some relevant applications, including CO_2 capture, O_2 purification, separation of light hydrocarbons, separation of noble gases, storage of gases(CH_4,H_2, and C_2 H_2) for energy, and removal of some gaseous air pollutants(NH_3, NO_2, and SO_2). Finally, an outlook regarding the challenges of the future research of MOFs in these directions is given.

Preface to Special Issue on Environmental and Energy Catalysis

Environmental pollution and energy storage are two major challenges faced by human beings.The magnitude of them is ever‐increasing due to rapid pace of urbanization and industrialization.In view of this,to achieve green environment and provide clean energy for human beings are pivotal for sustainability.The catalysis technology plays dominant role in addressing these issues.The nano/microstructured catalyst with intriguing physical and chemical properties could offer numerous opportunities to realize environmental sustainability and clean energy production.In the past two decades,great advances have been made on the design,synthesis and mechanistic understanding of typical catalysts for environmental and energetic applications.These new catalysts in various fashions can be classified into three main types,thermal catalysis,photocatalysis and electro catalysis.In some cases,two types can be combined together,such as photoelectrocatalysis and photothermal catalysis,to achieve higher catalysis efficiency.The features of catalysts can be further tailored to allow for enhanced catalytic performance in pollutant degradation and energy conversion.Advanced in situ techniques have been applied to explore and reveal the catalytic mechanisms.

Synthesis and electrochemical performance of LiCoPO_4 micron-rods by dispersant-aided hydrothermal method for lithium ion batteries

LiCoPO4 micron-rods with an average diameter of about 500 nm and length of about 5 μm were synthesized by dispersant-aided hydrothermal method. Poly(n-vinylpyrrolidone) (PVP) was used as dispersant in the hydrothermal method. The starting solution and the concentration of dispersant have significant influences on the morphology of LiCoPO4,and the electrochemical performance is improved via controlling the particle size and morphology by the hydrothermal method. The cell using smaller particle LiCoPO4 as cat...

Preparation, characterization and electrochemical properties of mesoporous LiFe_(0.99)Mo_(0.01)PO_4/C

A mesoporous LiFe0.99Mo0.01PO4/C composite was synthesized by the sol-gel method using （NH4）2MoO4 as a doping starting material. The formation of conductive carbon, metal doping and mesopores was achieved simultaneously in the prepared material. The characterizations of crystal structures and microstructures were investigated using X-ray diffraction （XRD）, scanning electron microscopy （SEM）, transmission electron microscopy （TEM）, extended X-ray-absorption fine-structure （EXAFS） and X-ray-absorption near-structure spectroscopy （XANES） while the surface area was determined using N2 adsorption techniques. Cyclic voltammetry （CV） and charge-discharge cycling performance were used to characterize its electrochemical properties. The sample possessed uniformly distributed mesopores with an average pore size of 4 nm, and the specific surface area was about 69.368 m^2/g. The results show that the reversible capacity of mesoporous LiFe0.99Mo0.01PO4/C is about 160 mAh/g at 0.1C, 135 mAh/g at 1C and 90 mAh/g at 5C, respectively. The capacity fading is neglectable.

Surfactant-aided hydrothermal preparation of La(2-x)Sr_xCuO_4 single crystallites and their catalytic performance on methane combustion

Perovskite-like oxide La2-xSrxCuO4 （x = 0, 1） single crystallites with microrod-like morphologies and tetragonal crystal structures were prepared hydrothermally at 240 ℃ with poly（ethylene glycol） （PEG） or hexadecyltrimethyl ammonium bromide （CTAB） as a surfactant and after calcination at 850 ℃. The physicochemical properties of the materials were characterized by means of XRD, BET, SEM, TEM/SAED （selected-area electron diffraction）, XPS and H2-TPR techniques. It is found that doping Sr2＋ to La2CuO4 lattice enhanced the catalytic activity for methane combustion and the LaSrCuO4 catalyst derived from PEG is the best among the tested ones. It is concluded that factors, such as adsorbed oxygen species concentration, reducibility and surface area, determined the catalytic performance of such single-crystalline materials.

The potential of pervaporation for biofuel recovery from fermentation:An energy consumption point of view

Recovering alcohols from dilute fermentation broth is an emergent task in bio-fuel production process. Since they are primary planned for fuels, energy required to separate these alcohols should be considered in evaluating the potential of a separation technology. A membrane-based process, pervaporation, is of special interest because of its environmental friendliness and easy integrating character. This review probes into the fundamentals of pervaporation especially in terms of the heat required for evaporation. Meanwhile, the separation data of the most representative alcohol-selective pervaporation membranes reported in the literatures are collected and compared with the vapor–liquid equilibrium curve, which represents the distillation selectivity. They include:inorganic membranes, silicon rubber based membranes, Mixed Matrix Membranes and some other special materials. By doing so, the status of alcohol recovery via pervaporation would be more clear for researchers.For ethanol recovery, it is selectivity rather than flux that is in urgent need of solution. While for butanol recovery,membranes with satisfactory selectivity have been developed, increasing the separation capacity would be more pressing.

A comparative investigation of NdSrCu_(1-x) Co_x O_(4-δ) and Sm_(1.8) Ce_(0.2) Cu_(1-x) Co_x O_(4-δ) (x:0–0.4) for NO decomposition

A series of single-phase T-structured NdSrCu 1-x Co x O 4-δ with oxygen vacancies and T -structured Sm 1.8 Ce 0.2 Cu 1-x Co x O 4-δ （x： 0–0.4） with oxygen excess were prepared using ultrasound-assisted citric acid complexing method, and characterized by means of techniques such as thermogravimetric analysis and NO temperature-programmed desorption （NO-TPD）. The catalytic activities of these materials were evaluated for the decomposition of NO. It was found that the NdSrCu 1-x Co x O 4-δ catalysts were of oxygen vacancies whereas the Sm 1.8 Ce 0.2 Cu 1？x Co x O 4-δ ones possessed excessive oxygen （i.e., over-stoichiometric oxygen）; with a rise in Co doping level, the oxygen vacancy density of NdSrCu 1-x Co x O 4-δ decreased while the over-stoichiometric oxygen amount of Sm 1.8 Ce 0.2 Cu 1-x Co x O 4-δ increased. The NO-TPD results revealed that NO could be activated much easier over the oxygen-deficient perovskite-like oxides than over the oxygen-excessive perovskite-like oxides, with the NdSrCuO 3.702 catalyst showing the best efficiency in activating NO molecules. Under the conditions of 1.0% NO/helium, 2800 hr -1 , and 600–900°C, the catalytic activity of NO decomposition followed the order of NdSrCuO 3.702 〉 NdSrCu 0.8 Co 0.2 O 3.736 〉 NdSrCu 0.6 Co 0.4 O 3.789 〉 Sm 1.8 Ce 0.2 Cu 0.6 Co 0.4 O 4.187 〉 Sm 1.8 Ce 0.2 Cu 0.8 Co 0.2 O 4.104 〉 Sm 1.8 Ce 0.2 CuO 4.045 , in concord with the sequence of decreasing oxygen vacancy or oxygen excess density. Based on the results, we concluded that the higher oxygen vacancy density and the stronger Cu 3＋ /Cu 2＋ redox ability of NdSrCu 1-x Co x O 4-δ account for the easier activation of NO and consequently improve the catalytic activity of NO decomposition over the catalysts.

Synthesis,structures,thermal and magnetic properties of a series of lanthanide Ln=Sm,Gd,Er,Yb complexes with 4-quinolineacarboxylate

A series of lanthanide binuclear complexes, Ln2（L）6（H2O）4·2H2O（Ln=Sm（Ⅲ）, Gd（Ⅲ）, Er（Ⅲ）, Yb（Ⅲ）, HL=4-quinolinea-carboxylic acid, were synthesized by reactions of corresponding rare earth salts with 4-quinolineacarboxylic acid at room temperature and were characterized by elemental analysis, IR spectroscopy, and single-crystal X-ray diffraction.X-ray diffraction analyses showed that they exhibited the same binuclear architecture and crystallized in monoclinic system and P21/c space group.In four complexes, each metal center adopted nine-coordinated mode coordinated by nine O atoms from two H2O molecules and three carboxyls of three ligands, and HL showed three different coordination modes.The variable-temperature magnetic susceptibility showed that complex Gd2（L）6（H2O）4·2H2O performed very weak antiferromagnetic property at low temperature and exchange was almost paramagnetic at high temperature.Complexes Er2（L）6（H2O）4·2H2O and Yb2（L）6（H2O）4·2H2O performed dominating antiferromagnetic coupling.

Enhanced catalytic performance of Cu-and/or Mn-loaded Fe-Sep catalysts for the oxidation of CO and ethyl acetate

The Fe-modi fied sepiolite-supported Mn–Cu mixed oxide(Cux Mny/Fe-Sep) catalysts were prepared using the co-precipitation method.These materials were characterized by means of the XRD,N_2 adsorption–desorption,XPS,H_2-TPR,and O_2-TPD techniques,and their catalytic activities for CO and ethyl acetate oxidation were evaluated.The results show that catalytic activities of the Cux Mny/Fe-Sep samples were higher than those of the Cu1/Fe-Sep and Mn2/Fe-Sep samples,and the Mn/Cu molar ratio had a distinct in fluence on catalytic activity of the sample.Among the Cux Mny/Fe-Sep and Cu1Mn2/Sep samples,Cu1Mn2/Fe-Sep performed the best for CO and ethyl acetate oxidation,showing the highest reaction rate and the lowest T50 and T90 of 4.4×10^(-6) mmol·g-1·s-1,110,and 140 °C for CO oxidation,and 1.9×10^(-6) mmol·g-1·s-1,170,and210 °C for ethyl acetate oxidation,respectively.Moreover,the Cu1Mn2/Fe-Sep sample possessed the best lowtemperature reducibility and the lowest temperature of oxygen desorption as well as the highest surface Mn^(4+)/Mn^(3+) and Cu^(2+)/CuO atomic ratios.It is concluded that factors,such as the strong interaction between the Cu or Mn and the Fe-Sep support,good low-temperature reducibility,and good mobility of chemisorbed oxygen species,might account for the excellent catalytic activity of Cu1Mn2/Fe-Sep.

Preparation and electrocatalytic property of Au-Pt/SnO_2/GC composite electrode

Au-Pt/SnO2/GC composite electrode was prepared by self-assembling Au-Pt nanoparticles on SnO2 film, which was deposited on actived glassy carbon （GC）. Atomic force microscopy （AFM） and scanning electron microscopy （SEM） images revealed that dense and uniform Au-Pt particles with 25-nm diameter were dispersed on SnO2 film. X-ray photoelectron spectroscopy （XPS） results proved that there was an interaction between Au-Pt nanoparticles and SnO2 support. Electrochemical experiments showed that Au-Pt/SnOz/GC composite electrode had a good electrocatalytic activity to the oxidation of methanol

Synthesis and Structure of a La(Ⅲ) Complex of 1,10-Phenanthroline-2,9-dicarboxylate:a Three-dimensional Network via Hydrogen Bonding Interactions

A new La（Ⅲ） complex, {[La（L）（NO3）（H2O）3]·H2O}n （L = 1,10-phenanthroline- 2,9-dicarboxylate）, has been synthesized and structurally determined by X-ray diffraction analysis. The complex crystallizes in the monoclinic system, space group P21/c with a = 7.7358（17）, b = 8.1664（18）, c = 28.271（6） A, β= 95.184（4）°, V= 1778.6（7） A3, Z = 4, C14H14LaN3O11, Mr = 539.19, Dc = 2.014 g/cm^3, μ= 2.471 mm^-1, F（000） = 1056, the final R = 0.0350 and wR = 0.0659. In this complex, each metal center adopts a ten-coordination geometry formed by two N atoms from a ligand L and eight O atoms from three H2O molecules, a nitrate ion and carboxylates of two ligands. Each ligand adopts a N2,O3-pentdentate coordination mode using two N and two O atoms chelating a La（Ⅲ）, and using another O atom of carboxylate to bridge another La（Ⅲ） center resulting in a 1D helical chain molecule. Intermolecular strong O-H…O and weak C-H…O hydrogen bonds extend the 1D chain structure into a 3D supramolecular architecture.

Syntheses,Characterization and Crystal Structures of Dithiocarbamate-based Mononuclear Palladium(Ⅱ) Complexes

By employing the dithiocarbamate salt （K（PPDC）, where PPDC = 4？-pyridyl-1-pipe-razine-4-dithiocarbamate） as the functional ligand and di-palladium complexes [（N^N）2Pd2（NO3ˉ）2]（NO3ˉ）2 （N^N = 2,2＇-bipyridine, bpy; 4,4＇-dimethylbipyridine, dmbpy） as corner, two novel single metal complexes with Pd（II） centers have been obtained. These organic-metal complexes were characterized by NMR, ESI-MS, elemental analysis, Uv-vis spectra and single-crystal X-ray diffraction analysis. Compound 1？（PF6）2 （[（bpy）Pd（PPDC）]·（PF6）2） crystallizes in triclinic, space group P , a = 8.3968（5）, b = 11.5565（7）, c = 18.2234（11）, α = 97.505（1）, β = 91.424（1）, γ = 106.146（1）o, C22H24N6S2P2F12Pd, Mr = 832.93, V = 1680.58（18） ？3, Z = 2, Dc = 1.646 Mg/m3, μ（MoKα） = 0.863 mm-1, F（000） = 828, the final R = 0.0455 and wR = 0.1390 for 6981 observed reflections with I 〉 2σ（I）. Similarly, compound 2？（PF6）2 （[（dmbpy）Pd（PPDC）]·（PF6）2） also crystallizes in triclinic, space group P , a = 13.9467（3）, b = 14.8390（2）, c = 17.0632（3） ？, α = 81.8680（10）, β = 87.051（2）, γ = 83.4590（10）o, C22H25N5S2P2F12Pd, Mr = 819.93, V = 3470.81（11） ？3, Z = 4, Dc = 1.569 Mg/m3, μ（CuKα） = 7.115 mm-1, F（000） = 1632, the final R = 0.0606 and wR = 0.1637 for 12835 observed reflections with I 〉 2σ（I）. Crystallography reveals that each metal center coordinates with two N atoms from bpy and two S atoms from PPDC in the square coordination mode. In the crystal structure of complex 1, a weak Pd……Pd interaction can be observed. Interestingly, it was also found that the mononuclear moieties of complex 2 could be packed into a 3-D porous framework via multiple intermolecular C–F……H hydrogen-boding interactions which extended in the a, b, and c axes with PF6ˉ anions frozen inside.

Design of a stearic acid/boron nitride/expanded graphite multifiller synergistic composite phase change material for thermal energy storage

In order to solve the problems of low thermal conductivity and easy liquid leakage of a stearic acid(SA),the composite phase change material(PCM)was prepared by adding boron nitride(BN)and expanded graphite(EG)to melted SA,and its thermal conductivity,crystal structure,chemical stability,thermal stability,cycle stability,leakage characteristics,heat storage/release characteristics,and temperature response characteristics were char-acterized.The results showed that the addition of BN and EG significantly improved the thermal conductivity of the material,and they efficiently adsorbed melted SA.The maximum load of SA was 76 wt.%and there was almost no liquid leakage.Moreover,the melting enthalpy and temperature were 154.20 J·g^(−1) and 67.85℃,re-spectively.Compared with pure SA,the SA/BN/EG composite showed a lower melting temperature and a higher freezing temperature.In addition,when the mass fraction of BN and EG was 12 wt.%,the thermal conductivity of the composite was 6.349 W·m^(−1)·K^(−1),which was 18.619 times that of SA.More importantly,the composite showed good stability for 50 cycles of heating and cooling,and the SA/BN/EG-12 hardly decomposes below 200℃,which implies that the working performance of the composite PCM is relatively stable within the tem-perature range of 100℃.Therefore,the composite can exhibit excellent thermal stability in the field of building heating.

Organic matter and concentrated nitrogen removal by shortcut nitrification and denitrification from mature municipal landfill leachate

An UASB＋Anoxic/Oxic （A/O） system was introduced to treat a mature landfill leachate with low carbon-to-nitrogen ratio and high ammonia concentration. To make the best use of the biodegradable COD in the leaehate, the denitrifieation of NOx^--N in the reeireulation effluent from the elarifier was carried out in the UASB. The results showed that most biodegradable organic matters were removed by the denitrifieation in the UASB. The NH4^＋-N loading rate （ALR） of A/O reactor and operational temperature was 0.28- 0.60 kg NH4^＋-N/（m^3-d） and 17-29℃ during experimental period, respectively. The short-cut nitrification with nitrite accumulation efficiency of 90%-99% was stabilized during the whole experiment. The NH4^＋-N removal efficiency varied between 90% and 100%. When ALR was less than 0.45 kg NH4^＋-N/（m^3.d）, the NH4^＋-N removal efficiency was more than 98%. With the influent NH4^＋-N of 1200-1800 mg/L, the effluent NH4^＋-N was less than 15 mg/L. The shortcut nitrification and denitrifieation can save 40% carbon source, with a highly efficient denitrifieation taking place in the UASB. When the ratio of the feed COD to feed NH4^＋-N was only 2-3, the total inorganic nitrogen （TIN） removal efficiency attained 67%-80%. Besides, the sludge samples from A/O reactor were analyzed using FISH. The FISH analysis revealed that ammonia oxidation bacteria （AOB） accounted for 4% of the total eubaeterial population, whereas nitrite oxidation bacteria （NOB） accounted only for 0.2% of the total eubaeterial population.

Recent developments in nanofiltration membranes based on nanomaterials

Nanofiltration membranes are the core elements for nanofiltration process. The chemical structures and physical properties of nanofiltration membranes determine water permeability, solute selectivity, mechanical/thermal stability, and antifouling properties, which greatly influence the separation efficiency and operation cost in nanofiltration applications. In recent years, a great progress has been made in the development of high performance nanofiltration membranes based on nanomaterials. Considering the increasing interest in this field, this paper reviews the recent studies on the nanofiltration membranes comprising various nanomaterials, including the metal and metal oxide nanoparticles, carbon-based nanomaterials, metal–organic frameworks(MOFs), water channel proteins, and organic micro/nanoparticles. Finally, a perspective is given on the further exploitation of advanced nanomaterials and novel strategy for fabricating nano-based nanofiltration membranes. Moreover,the development of precision instruments and simulation techniques is necessary for the characterization of membrane microstructure and investigation of the separation and antifouling mechanism of nanofiltration membranes prepared with nanomaterials.

Characteristics of a Supersonic Swirling Dehydration System of Natural Gas

A new type of dehydration unit for natural gas was briefly described and its basic structure and working principles were presented. An indoor test rig for testing the unit performance was set up and the experimental results were given. The results showed that the unit could attain a maximum dew point depression of about 20~C without any need of external mechanical power and chemicals. The pressure loss ratio, shock wave and the flow rate had great influence on the dehydration characteristics. From the systematic analysis of the factors that affect the dehydration efficiency of the unit, the suggestions for improving the unit are put forward.

Nitrogen Removal by Simultaneous Nitrification and Denitrification via Nitrite in a Sequence Hybrid Biological Reactor

顺序混血儿生物反应堆(SHBR ) 被建议，并且一些关键控制参数被同时的氮的硝化作用和 denitrification (SND ) 经由亚硝酸根从废水为氮移动调查。经由亚硝酸根的 SND 被控制需求氧在 SHBR 完成() 集中。有从 2.50 mg 路 L 的 DO 的规划减少 ? 1 ～ 0.30 mg 路 L ? 1，并且平均亚硝酸根累积率(NAR ) 在 3 个星期内从 16.5% ～ 95.5% 被增加。随后，进一步增加在做集中到 1.50 mg 路 L ? 1 没破坏部分氮的硝化作用到亚硝酸根。结果显示出那有限空气流动率到在反应堆的氧缺乏将最后导致的原因仅仅氮的硝化作用到亚硝酸根并且不进一步。氮移动效率随 NAR 的增加被增加，也就是说， NAR 从 60% ～ 90% 被增加，并且全部的氮移动效率从 68% ～ 85% 被增加。 SHBR 能容忍分别地，高器官的装载率( OLR )，货到付款和氨氮移动效率比92%和93.5%大并且它甚至操作了在下面低做集中( 0.5 mg 路L ? 1 )并且维持的高 OLR ( 4.0 kg 货到付款 路m ? 3 路d ? 1 )。biofilm 的存在断然影响了在从来没撞击的 SHBR 解决能力，和激活的污泥的污泥体积索引(SVI ) 的激活的污泥超过 90 ml 路 g ? 1 在整个实验。

Novel strategy of nitrogen removal from domestic wastewater using pilot Orbal oxidation ditch

A pilot-scale Orbed oxidation ditch was operated for 17 months to optimize nitrogen removal from domestic wastewater of average COD to total nitrogen ratio of 2.7, with particular concern about the roles of dissolved oxygen （DO）, mixed liquor suspended solids （MLSS） and return activated sludge （RAS） recycle ratio. Remarkable simultaneous nitrification and denitrification （SND） was observed and mean total nitrogen （TN） removal efficiency up to 72.1% was steadily achieved, at DO concentration in the out, middle and inner channel of 0.1, 0.4 and 0.7 mg/L, respectively, with an average M LSS of 5.5 g/L and RAS recycle ratio of 150%. Although the out channel took the major role in TN removal, the role of middle channel should never be ignored. The denitrification potential could be fully developed under low DO, high MLSS with adequate RAS ratio. The sludge settleability was amazingly improved under low DO operation mode, and some explanations were tried. In addition, a scries of simplified batch tests were done to determine whether novel microorganisms could make substantial contribution to the performance of nitrogen removal. The results indicated that the SND observed in this Orbal oxidation ditch was more likely a physical phenomenon.

Achieving and maintaining biological nitrogen removal via nitrite under normal conditions

The principal aim of this paper is to develop an approach to realize stable biological nitrogen removal via nitrite under normal conditions. Validation of the new method was established on laboratory-scale experiments applying the sequencing batch reactor（SBR） activated sludge process to domestic wastewater with low C/N ratio. The addition of sodium chloride（NaCI） to influent was established to achieve nitrite build-up. The high nitrite accumulation, depending on the salinity in influent and the application duration of salt, was obtained in SBRs treating saline wastewater. The maintenance results indicated that the real-time SBRs can maintain stable nitrite accumulation, but conversion from shorter nitrification-denitrification to full nitrification-denitrification was observed after some operation cycles in the other SBR with fixed-time control. The presented method is valuable to offer a solution to realize and to maintain nitrogen removal via nitrite under normal conditions.