Ionothermal synthesis of gallophosphate molecular sieves in 1-alkyl-3-methyl imidazolium bromide ionic liquids

Gallophosphate (GaPO₄) molecular sieves were ionothermally prepared in 1-alkyl-3-methyl imidazolium bromide ionic liquids (ILs) with alkyl chain length varying from 2 to 6 carbons for the first time. Three kinds of GaPO₄ materials such as GaPO₄-a, cloverite (denoted as CLO below) and GaPO₄-LTA were obtained, and their structures and morphologies were characterized by powder and single crystal XRD, SEM and multi-nuclear NMR. In the case of 1-ethyl-3-methyl imidazolium bromide ionic liquid, large single crystals of GaPO₄-LTA with well-defined octahedral morphology was obtained in both sealed (ca. 400 μm in size) and open vessels (ca. 300 μm in size). Ionothermal synthesis is an effective method for the preparation of large single crystal of molecular sieves. With the alkyl chain length of the ionic liquids increasing from 2 carbons to 6 carbons, the size of GaPO₄-LTA decreased sharply. The organic template cations in the as-synthesized GaPO₄-LTA crystals may have two different kinds of conformational structures. Fluorine plays a role of co-template along with organic cations of ILs in the synthesis of GaPO₄-LTA and CLO, while only GaPO₄-a was obtained in the absence of fluorine. The reaction temperature can also affect the structure of the final structure. In the reaction medium of 1-ethyl-3-methyl imidazolium bromide IL, GaPO₄-LTA was obtained at 180 °C, while CLO was obtained at 150 °C.     

Ionothermal synthesis of a three-dimensional zinc phosphate with DFT topology using unstable deep-eutectic solvent as template-delivery agent

A three-dimensional zinc phosphate compound with DFT topology, designated as ZnPO₄-EU1, has been synthesized by an ionothermal approach from the system HF-ZnO–P₂O₅-choline chloride-imidazolidone. Ethylenediamine, derived from decomposition of the imidazolidone component of the deep-eutectic solvent (DES) itself, is delivered to the synthesis and serves as an appropriate template for ZnPO₄-EU1. Experiments in which the synthesis conditions were varied showed that ZnPO₄-EU1 may be prepared over a wide molar ratio of P/Zn = 0.55–13.0. Powder X-ray diffraction patterns have been obtained at intervals to track the crystallization process of this material. The experimental data show that Zn₃(PO₄)₂ · 4H₂O (a dense phase) was first isolated from the DES after reaction for 1 h. Subsequently, the pure phase of ZnPO₄-EU1 was obtained with increasing crystallization time from 12 h to 72 h. The experimental results show that the nucleation and crystallization take place with relatively low levels of solvent degradation, demonstrating that zinc phosphate with a three-dimensional framework can be synthesized by in situ generation of an appropriate template using an unstable DES at high temperatures (150–200 °C).     

Ionothermal synthesis and characterization of a 3-D (4, 8)-connected porous anionic metal–organic framework entrapped with 1-D [K2(H2O)6] chains

A novel metal–organic coordination polymer, namely, {[K₂(H₂O)₆][Cd₃(1,2,4,5-BTC)₂]}_n (1) (1,2,4,5-BTC = 1,2,4,5-benzenetetracarboxylate), was synthesized in an ionothermal reaction by using an ionic liquid 1-ethyl-3-methylimidazolium bromide ([EMIM]Br) as solvent. Complex 1 features a novel 3-D (4, 8)-connected porous anionic architecture constructed by linking trinuclear Cd subunits with 1,2,4,5-BTC⁴⁻ ligands, which are further filled with 1-D [K₂(H₂O)₆] cationic chains.     

高岭土微球离子热法原位合成SAPO-34分子筛

在季戊四醇和四乙基氯化铵低共融混合物中,采用离子热法将苏州高岭土为主要原料的微球原位晶化制备了SAPO-34分子筛微球。考察了晶化条件和晶化液对原位合成的影响。通过XRD和SEM等手段对合成的微球进行了表征。实验结果表明,在晶化温度为180 ℃下,晶化液物质的量比为n（二氧化硅）∶n（氧化铝）∶n（五氧化二磷）∶n［N-甲基咪唑（2-甲基咪唑）］∶n（氟化氢）∶n（水）=2.26∶1∶0.5∶0.66∶0.3∶26.4时,晶化20 h可以合成出SAPO-34分子筛微球。加入导向剂N-甲基咪唑和2-甲基咪唑有利于SAPO-34分子筛的合成。     

Adsorption removal of o-nitrophenol and p-nitrophenol from wastewater by metal–organic framework Cr-BDC

In the present paper, a metal–organic framework Cr-BDC was prepared and used as adsorbent for adsorption of o-nitrophenol(ONP) and p-nitrophenol(PNP) from aqueous solutions. Cr-BDC was characterized by scanning electron microscopy, transmission electron microscope, X-ray diffraction and BET methods. The results indicate that Cr-BDC gets a very large specific surface area of 4128 m~2·g~(-1)and pore sizes are concentrated in 1 nm, which is a benefit for using for wastewater treatment. The influences of the adsorption conditions, such as temperature,solution concentration, adsorption time and reusability on adsorption performance were investigated. Cr-BDC exhibited an encouraging uptake capacity of 310.0 mg·g~(-1)for ONP, and adsorption capacity of Cr-BDC for ONP is significantly higher than that for PNP under suitable adsorption conditions. The characterizations of adsorption process were examined with the Lagergren pseudo-first-order, the pseudo-second-order kinetic model, and the intra-particular diffusion model. Kinetics experiments indicated that the pseudo-second-order model displayed the best correlation with adsorption kinetics data. Furthermore, our adsorption equilibrium data could be better described by the Freundlich equation. The results indicate that the as-prepared Cr-BDC is promising for use as an effective and economical adsorbent for ONP removal.     

Recent advances of ammonia synthesis under ambient conditions over metal-organic framework based electrocatalysts

Ammonia (NH₃) is an essential chemical and a promising fuel, but its industrially produced process is carbon-intensive and highly energy-consuming. Developing a green and sustainable NH₃ synthesis route is extremely urgent. Electrochemical ammonia synthesis (EAS) powered by renewable electricity energy under ambient conditions is fascinating, while exploring the efficient electrocatalysts and suitable nitrogen source is critical. Due to the unique characteristics of adjustable porosity and component, large specific surface area and diverse structure, metal-organic frameworks (MOFs) and their various derivatives have captured immense interest in EAS. Herein, the advance in EAS via electrocatalytic reduction reactions (ERRs) from various nitrogen source under ambient conditions over MOF-based electrocatalysts is timely summarized, aiming to offer a deep insight to the structure-activity relationship of MOF-based electrocatalysts for EAS. Current challenges and future prospects for EAS are proposed at the end of this review as well.     

Ionothermal synthesis of a 3D Zn–BTC metal-organic framework with distorted tetranuclear [Zn4(μ4-O)] subunits

A zinc metal-organic framework (MOF), [Zn₄(BTC)₂(μ₄-O)(H₂O)₂], was synthesized with Zn(NO₃)₂ · 6H₂O and H₃BTC ligand (H₃BTC = 1,3,5-benzenetricarboxylic acid) by ionothermal synthesis in 1-ethyl-3-methylimidazolium bromide ionic liquid as solvent. The compound features a 3-D architecture constructed by linking [Zn₄(μ₄-O)] subunits with BTC³⁻ ligands. They are composed of two five-coordinated and two four-coordinated Zn ions, different from the [Zn₄(μ₄-O)] units of other MOFs. The effect of reaction conditions to the MOF structure is discussed.     

新型钴基费托合成催化剂的制备与表征

用CoC l3.6H2O和K2S iO3水玻璃共沉淀法制备出了一种蒙脱土结构的新型催化剂。用XRD、SEM和氮气的低温吸附脱附等方法对催化剂的物相结构进行测定,确认该催化剂具有层状结构并有较高的比表面积。经过催化剂的前处理,FT合成在浆态床反应器中进行。反应条件为270℃,0.5 MPa,H2/CO=2,反应时间为6 h。产物分析得知C9~C25烃类的选择性达到了90%以上。     

Ionothermal synthesis of aluminophosphates used for ion exchange: Influence of choline chloride/urea ratio

A wide variety of industrial processes produce aqueous effluents that contain heavy metals. Considering the toxicity of metal polluted wastewaters, ion exchange appears as an easy and inexpensive option to remove metal ions from these effluents. There is currently much investigation on synthetic and natural materials to be used as cation exchangers. Among these materials, using microporous molecular sieves have been proposed due to their high surface area, porous diameter and ion exchange capacity. In this work, aluminophosphates (AlPOs) were prepared by the ionothermal method using the eutectic mixture urea/choline chloride (CCh) as solvent and template. Different CCh ratios in the eutectic mixture used in gel synthesis resulted in different structures with very distinguished ion exchange capacities. The main structures obtained were SIZ-2 and AlPO-CJ2. Varying the percentage of CCh in the gel synthesis mixture, it was observed that the AlPO-CJ2 structure is obtained using CCh percentages greater than 50%, while SIZ-2 is obtained using 25% and 33.3% CCh. The structure-directing the interrupted structure are the ammonium cations coming from the partial decomposition of urea. The SIZ-2 prepared using 25% CCh has a somewhat higher ion exchange capacity than that observed using 33.3% CCh. This result is very interesting since CCh is the most expensive component in the eutectic mixture.     

晶种法合成金属骨架材料MIL-53-Cu的初步研究

通过水热方法及晶种法合成了MIL-53-Cu样品。通过X射线衍射仪(XRD)、傅里叶变换红外光谱仪(FT-IR)、扫描电镜显微镜(SEM)等对样品进行了结构表征。结果表明晶种法与水热合成法合成出来的样品在结构、形貌上相符合,但晶种法的合成时间显著减少。晶种合成法有望成为MIL系列材料主流的合成方法。     

Three metal-organic frameworks prepared from mixed solvents of DMF and HAc

Three metal-organic framework compounds [HZn₃(OH)(BTC)₂(2H₂O) (DMF)] · H₂O (MOF-CJ3), [Co₆(BTC)₂(HCOO)₆(DMF)₆] (MOF-CJ4), and [Co₁₈(HCOO)₃₆] · 3H₂O (MOF-CJ5) have been solvothermally synthesized in mixed solvents of DMF and HAc, respectively. These MOFs are characterized by single-crystal X-ray diffraction, X-ray powder diffraction, ICP, TG analyses, IR, and photoluminescence spectroscopy analyses. MOF-CJ3 crystallizes in tetragonal, space group I4cm (No. 108) with a = 20.588(3) Å, b = 20.588(3) Å, c = 17.832(4) Å. Its framework can be described as a 3D decorated (3, 6)-connected net based on the assembly of trigonal prismatic SBUs and triangular links. MOF-CJ4 crystallizes in hexagonal, space group P-3 (No. 147) with a = 13.975(2) Å, b = 13.975(2) Å, c = 8.1650(16) Å. The 2D network of MOF-CJ4 is constructed from [Co₆(R(CO₂)₃)₂(HCO₂)₆(DMF)₆] (R = C₉H₃–) clusters and 1,3,5-benzene-tricarboxylates linkers. MOF-CJ5 crystallizes in triclinic, space group (No. 2) with a = 15.205(3) Å, b = 18.005(4) Å, c = 21.500(4) Å,  = 71.21(3)°, β = 84.47(3)°, γ = 67.15(3)°. MOF-CJ5 has a diamond framework with Co-centered CoCo₄ tetrahedra as nodes. It is noteworthy that the formic ligands in MOF-CJ4 and MOF-CJ5 are generated by the decomposition of DMF under acid conditions and incorporated into these two compounds.     

Adsorption of selected dyes on Ti3C2Tx MXene and Al-based metal-organic framework

MXene and metal organic framework (MOF) were used as the main adsorbents to remove synthetic dyes from model wastewater. Methylene blue (MB) and acid blue 80 (AB) were used as the model cationic and anionic synthetic dyes, respectively. To investigate the physicochemical properties of the adsorbents used, we carried out several characterizations using microscopy, powder X-ray diffraction, a porosimetry, and a zeta potential analyzer. The surface area of MXene and MOF was 9 and 630 m² g⁻¹, respectively, and their respective isoelectric points were approximately pH 3 and 9. Thus, MXene and MOF exhibited high capacity for MB (~140 mg g⁻¹) and AB (~200 mg g⁻¹) adsorption, respectively due to their electrostatic attractions when the concentrations of the adsorbents and adsorbates were 25 and 10 mg L⁻¹. Furthermore, the MOF was able to capture the MB due mainly to hydrophobic interactions. In terms of the advantages of each adsorbent according to our experimental results, MXene exhibited fast kinetics and high selectivity. Meanwhile, the MOF had a high adsorption capacity for both MB and AB. The adsorption mechanisms of both adsorbents for the removal of MB and AB were clearly explained by the results of our analyses of solution pH, ionic strength, and the presence of divalent cation, anion, or humic acids, as well as other characterizations (i.e., Fourier-transform infrared spectroscopy and X-ray photoelectron spectroscopy). According to our results, MOF and MXene can be used as economical treatments for wastewater containing organic pollutants regardless of charge (e.g., MB and AB), and positively charged one (e.g., MB), respectively.     

Hybridization of metal–organic framework and monodisperse spherical silica for chromatographic separation of xylene isomers

Metal–organic frameworks(MOFs) packed in the column have been a promising candidate as the stationary phase for high performance liquid chromatography(HPLC). However, the direct packing of irregular MOF powder could raise some problems like high back pressure and low column efficiency in the HPLC separation. In this work, UiO-66 capable of separating xylenes was supported effectively on the surface of the monodisperse spherical silica microspheres by one-pot method. The hybridization of Ui O-66 and silica microspheres(termed UiO-66@SiO_2 shell–core composite) was prepared by stirring the suspension of the precursors of Ui O-66 and\\COOH terminated silica in the N,N-dimethylformamide with heating. The shell–core composite material UiO66@SiO_2 was characterized by SEM, TEM, PXRD and FTIR. Then, it was used as a packing material for the chromatographic separation of xylene isomers. Xylene isomers including o-xylene, m-xylene and p-xylene were efficiently separated on the column with high resolution and good reproducibility. Moreover, the Ui O-66@SiO_2 shell–core composites packed column still remained reverse shape selectivity as Ui O-66 possessed, and the retention of xylenes was probably ascribed to the hydrophobic effect between analytes and the aromatic rings of the Ui O-66 shell. The Ui O-66@SiO_2 shell–core composites obtained in this study have some potential for the separation of structural isomers in HPLC.     

Postsynthetic acid modification of amino-tagged metal-organic frameworks: Structure-functionrelationship for catalytic 5-hydroxymethylfurfural synthesis

Developing an efficient and selective catalyst for the dehydration of fructose to 5-hydroxymethylfurfural(HMF) is significant for biomass conversion. Herein, a metal-organic framework(MOF) with acidity and strong hydrophobicity is first reported by the condensation of amino-tagged MOFs with mercapto carboxylic acids and subsequent oxidation. The hydrophobic acidic MOFs possess acid densities ranging from 0.2-1.0 mmol·g^-1, H₂O contact angles of 114°-125°, and specific surfac...     

Dynamics of the fischer-tropsch synthesis over a supported cobalt catalyst

Step-change experiments between H₂, CO, and syngas mixtures with time resolution of ca. 0.3 s were undertaken to critically test mechanisms proposed in the literature for the Fischer-Tropsch synthesis. A silica-supported cobalt catalyst was used. Results suggest C₂₊ olefins and branched paraffins form from a carbon deposit on the catalyst surface. Two pathways appear to exist for methane formation. The first of these is from the carbon deposit through direct hydrogenation and through hydrogenolysis of the long-chain materials formed. The second pathway is hydrogenation of strongly adsorbed CO.     

Composition modulation of the fischer-tropsch synthesis over a supported cobalt catalyst

Different cycling strategies are explored to see if carbon chain growth can be enhanced and methane formation suppressed. Of the strategies considered, bang-bang cycling between H₂ and CO feeds substantially increased the consumption of CO and H₂, but the formation of higher hydrocarbons and olefins was reduced. The best strategy for longer chain hydrocarbons suitable for jet or diesel fuels was found to be cycling between syngas mixtures. None of the cycling strategies was able to produce C₈₊ or low-molar mass olefin yields that matched yields found in steady-state operation.     

Multivariate optimization of high removal of lead(Ⅱ) using an efficient synthesized Ni-based metal–organic framework adsorbent

A new metal-organic framework(MOF) with the chemical formula of [Ni_2 F_2(4,4'-Bipy)_2(H_2 O)_2](VO_3)_2·8 H_2 O was introduced to adsorb Pb(Ⅱ) with the highest capacity.The sorbent was characterized by thermogravimetric analysis(TGA),infrared spectroscopy(FT-IR),field-emission scanning electron microscopy(FESEM),energy-dispersive Xray(EDX),and elemental analysis.The optimum conditions were obtained by a face-centered central composite design(FCCD) as follows:adsorbent dosage(m)=1.2 mg, initial concentration of Pb(Ⅱ)(C)=390 mg·L~(-1),and pH=5.According to the Langmuir model(R~2=0.9999),the maximum monolayer uptake capacity of lead(Ⅱ) is 2400.7 mg·g~(-1),which is the highe st observed amount for lead(Ⅱ) adsorption.Neither of the old adsorbents for lead(Ⅱ)has the uptake capacity over 2000 mg·g~(-1).The model of pseudo-second-order describes well the process kinetics.The adsorption process of lead(Ⅱ) is independent of temperature changes.This compound can adsorb lead(Ⅱ) from tap water.In addition to introducing a new MOF with the highest uptake capacity for removal of Pb(Ⅱ) that is the outright novelty of this study,the concurrent modeling of both the removal percent(R) and the uptake capacity(q) is another important advantage.Because it achieves the more economical and favorable optimum conditions in comparison with the single optimization of each response.