One-step synthesis of a ZIF-8/90-based type I porous liquid.

A Type I porous liquid based on the mixed-linker zeolitic imidazolate framework, ZIF-8/90-PL, has been prepared by a one-step imine condensation reaction and characterized by X-ray diffraction, FT-IR spectroscopy, TGA and rheology analysis. This facile preparation strategy of a porous liquid has enormous industrial production and application potential, with over one kilogram of ZIF-8/90-PL being successfully prepared. ZIF-8/90-PL can be directly used as a liquid absorbent or be co-processed with alumina hollow fibers to form a composite membrane with improved selectivity in the context of CO2 separation from CH4 or N2. This simple synthesis method is expected to be extended to other metal-organic frameworks.

Synergy of Paired Brønsted-Lewis Acid Sites on Defects of Zr-MIL-140A for Methanol Dehydration.

As a common defect-capping ligand in metal-organic frameworks (MOFs), the hydroxyl group normally exhibits Brønsted acidity or basicity, but the presence of inherent hydroxyl groups in the MOF structure makes it a great challenge to identify the exact role of defect-capping hydroxyl groups in catalysis. Herein, we used hydroxyl-free MIL-140A as the platform to generate terminal hydroxyl groups on defect sites via a continuous post-synthetic treatment. The structure and acidity of MIL-140A were properly characterized. The hydroxyl-contained MIL-140A-OH exhibited 4.6-fold higher activity than the pristine MIL-140A in methanol dehydration. Spectroscopic and computational investigations demonstrated that the reaction was initiated by the respective adsorption of two methanol molecules on the terminal-OH and the adjacent Zr vacancy. The dehydration of the adsorbed methanol molecules then occurred in the Brønsted-Lewis acid site co-participated associative pathway with the lowest energy barrier.

Novel Reactive Distillation Process for Cyclohexyl Acetate Production: Design, Optimization, and Control.

A side-reactor column (SRC) configuration, comprising a vacuum column coupled with atmospheric side reactors, is proposed to overcome the thermodynamic restriction in the esterification of cyclohexene with acetic acid to produce cyclohexyl acetate. Meantime, this configuration can avoid the utilization of the high-pressure steam and provide enough zone for catalyst loading. In order to obtain the minimum total annual cost (TAC), the process is optimized by a mixed-integer nonlinear programming optimization method based on the improved bat algorithm. The results indicate that the optimized SRC configuration saves about 44.81% of the TAC compared to the reactive distillation process. Based on the optimized SRC process, dynamic control is carried out. The dual-point temperature and temperature-composition control structures are proposed to reject throughput and feed composition disturbances. The dynamic performances demonstrate that the temperature-composition control structure is better in maintaining product purity.

Naphthenic Acids Removal from Model Transformer Oil by Diethylamine Modified Resins.

Resins have enormous potential in the removal of naphthenic acids (NAs) from transformer oil due to their rich porosity and high mechanical and diversified functionality, whereas their poor adsorption capacity limits application. In this work, the polystyrene-diethylamine resin (PS-DEA-x) was prepared by grafting diethylamine (DEA) onto chloromethylated polystyrene (PS-Cl) resin to efficiently adsorb cyclopentane carboxylic acid from transformer oil for the first time. The characterization analysis results indicated that amine contents were significantly enhanced with the increase in DEA. Particularly, resin with a molar ratio of 1:5 depending on chloromethyl to DEA (PS-DEA-5) exhibited the highest amine contents and efficient adsorption of cyclopentane carboxylic acid (static adsorption capacity up to 110.0 mg/g), which was about 5 times higher than that of the pristine PS-Cl. The thermodynamic and kinetic studies showed that the adsorption behaviors could be well fitted to the Langmuir isotherm equation and pseudo-second-order rate equation. Moreover, it was found that 1 g of the PS-DEA-5 can decontaminate about 760 mL transformer oil to meet reuse standards by a continuous stream, indicating its potential application in industry.

Fabricating defect-rich metal-organic frameworks via mixed linker-induced crystal transformation.

Defect-rich hcp UiO-66-NO2 was synthesized via mixed linker-induced crystal transformation from fcu UiO-66-NO2/NH2. The defect concentration and porosity of hcp UiO-66-NO2 can be fine-tuned by varying the BDC-NH2/BDC-NO2 ratio, which in turn endowed hcp UiO-66-NO2 with superior catalytic performance in the ring-opening reaction of epoxides with alcohols.

Type II porous ionic liquid based on metal-organic cages that enables L-tryptophan identification.

Porous liquids with chemical separation properties are quite well-studied in general, but there is only a handful of reports in the context of identification and separation of non-gaseous molecules. Herein, we report a Type II porous ionic liquid composed of coordination cages that exhibits exceptional selectivity towards L-tryptophan (L-Trp) over other aromatic amino acids. A previously known class of anionic organic-inorganic hybrid doughnut-like cage (HD) is dissolved in trihexyltetradecylphosphonium chloride (THTP_Cl). The resulting liquid, HD/THTP_Cl, is thereby composed of common components, facile to prepare, and exhibit room temperature fluidity. The permanent porosity is manifested by the high-pressure isotherm for CH4 and modeling studies. With evidence from time-dependent amino acid uptake, competitive extraction studies and molecular dynamic simulations, HD/THTP_Cl exhibit better selectivity towards L-Trp than other solid state sorbents, and we attribute it to not only the intrinsic porosity of HD but also the host-guest interactions between HD and L-Trp. Specifically, each HD unit is filled with nearly 5 L-Trp molecules, which is higher than the L-Trp occupation in the structure unit of other benchmark metal-organic frameworks.

La/LaF3 co-modified MIL-53(Cr) as an efficient adsorbent for the removal of tetracycline.

Chromium based metal-organic framework (MIL-53(Cr)) has enormous potential in the removal of organic contaminants from aqueous solutions due to its outstanding water stability, whereas its poor adsorption capacity limits the application. In this study, La/LaF3-MIL-53(Cr) was successfully synthesized by taking the advantages of La doping and LaF3 encapsulation with one-step hydrothermal method. Diverse analysis tools were utilized to verify that La not only existed in the framework, but also was loaded in the pores in the form of LaF3. The adsorption experiment results demonstrated that 0.3-La/LaF3-MIL-53(Cr) exhibited significantly improved adsorption capacity by four times compared with the pristine MIL-53(Cr) material. XPS and FTIR revealed that the affinity of La to tetracycline was significantly stronger than that of Cr and the excellent dispersion of LaF3 in the material may also be the cause of the increase in adsorption capacity. This study described a simple method to combine two different forms of modification and the modified material was potential for tetracycline adsorption.

Activated carbon prepared from catechol distillation residue for efficient adsorption of aromatic organic compounds from aqueous solution.

At present, activated carbon (AC) derived from industrial wastes has a great practical significance. In this work, residue activated carbon (RAC) was successfully synthesized from catechol distillation residue by a simple activation process based on two steps. The optimized RAC (RAC-800, activated at 800 °C) had high specific surface area (1800 m2/g) and large total pore volume (0.91 cm3/g). RAC-800 portrayed the evident increase of the graphitic structure and possessed abundant functional groups. Catechol (CC), phthalic acid (PA) and dimethyl phthalate (DMP) were chosen as typical pollutant to investigate the effect of different functional groups on adsorption aromatic compounds, and the equilibrium adsorption capacity of RAC-800 for CC, PA and DMP was 221.5, 365.0 and 449.9 mg/g, respectively. The adsorption behaviors were systematically studied by the combination of kinetic and thermodynamic model. The adsorption process was dominated by the π-π interaction, assisted by hydrogen bonding, hydrophobic and electrostatic interactions. In addition, regeneration study showed that the adsorption capacity can still remain over 88.5% after five cycles. In total, fine chemical distillation residues are promising to turn into the precursor of activated carbon, which has potential to be used as a good adsorbent for removal of aromatic compounds.

Simultaneous shaping and confinement of metal-organic polyhedra in alginate-SiO2 spheres.

The simultaneous shaping and confinement of Cu-based MOP in alginate-SiO2 spheres significantly enhance the mechanical strength and leaching resistance of Cu-MOP. The resulting MOP-alginate-SiO2 is shown through chemical fixation of CO2 to exhibit improved product yield over the parent Cu-MOP and Cu-alginate-SiO2.

Catalytic hydrolysis of ß-lactam antibiotics via MOF-derived MgO nanoparticles embedded on nanocast silica.

The antibiotics abuse and the proliferation of antibiotic-resistant bacteria in the environment have a severe impact on both human health and ecosystem. In this study, a silica-nanocasting method was applied in Mg-MOF-74 template to generate a series of MgO/SiO2 catalysts for the hydrolysis of ß-lactam antibiotics. The Mg-based subunits in MOF-74 were converted to highly dispersed MgO nanoparticles with controllable particle size. MgO/SiO2-80 with the smallest MgO particle size exhibits the best catalytic performance in the hydrolysis of four ß-lactam antibiotics. The kinetics study reveals the higher degradation rate and lower activation energy of MgO/SiO2-80 than other benchmark solid base catalysts. The proposed mechanism suggests that small MgO particle size provides more accessible oxygen anions with high proton affinity for the cleavage of the ß-lactam ring, so that all hydrolytic products lose antimicrobial activity. The MgO/SiO2-80 serves as the potential high-performance solid base catalyst for the real-world antibiotic wastewater treatment.

High-efficiency treatment of benzaldehyde residue using two-stage fluidized-bed/fixed-bed catalytic system.

A novel two-stage fluidized-bed/fixed-bed catalytic system was developed for the treatment of benzaldehyde residue. The effects of reaction temperature, oxygen concentration, space velocity on the purification of benzaldehyde production residue were investigated. The effluent chemical oxygen demand (COD) was less than 70 mgO2/L and the COD removal efficiency was higher than 99.83% under our experimental condition (fluidized-bed and fixed-bed temperature of 300-400°C, the flow rate of residue of 10 mL/h and O2 excessive rate of 20). The volatile organic compounds (VOCs) of the outlet were not detected after the treatment. The high-efficiency performance of the process can last for at least 600 h in the stability experiment. It was also verified by gas chromatography-mass spectrometry (GC-MS) analysis that most organic pollutants in the residue were significantly removed after treatment. These results suggest that the two-stage fluidized-bed/fixed-bed catalytic system could be a promising technology for the dispose of chlorine-containing polymer organics in the chemical industry.

Modulating the basicity of Zn-MOF-74 via cation exchange with calcium ions.

The fine-tuning of metal-based molecular building blocks in Zn-MOF-74 through post-synthetic cation exchange with Ca2+ significantly enhances its basicity and corresponding catalytic performance. The resulting material, exemplified by Ca/Zn-MOF-74, is shown through Knoevenagel condensation to give an improved product yield over the parent Zn-MOF-74 and Ni/Zn-MOF-74.

Solvent-Assisted Stepwise Redox Approach To Generate Zeolite NaA-Supported K2O as Strong Base Catalyst for Michael Addition of Ethyl Acrylate with Ethanol.

Solid base catalysts featuring green, robustness, and high activity play an important role in the current fine-chemical and petrochemical industry. Normally, the generation of supported K2O by thermal decomposition of KNO3 requires high temperature, and this process can sometimes destroy the structure of supporting materials. We herein report a solvent-assisted stepwise redox (SASR) approach to generate zeolite NaA-supported K2O, which we call K2O/NaA, that function as the solid base catalyst for Michael addition reaction between ethanol and ethyl acrylate. The solvent-assisted redox decomposition process of KNO3 at elevated temperature was investigated by thermogravimetry-mass spectrometry. It reveals that after reducing a minor amount of KNO3 at 400 °C, the organic solvent decomposes to form carbon, which promotes the reduction of KNO3 to generate strong basicity on the zeolite NaA at 600 °C. The resulting material, K2O/NaA-S, exhibits improved catalytic activity in Michael addition reaction over other benchmark base catalysts that have been used in this reaction. This catalyst is durable for at least four catalytic cycles without apparent loss in activity. K2O/NaA-S exhibits larger reaction rate constant yet lower activation energy than K2O/NaA prepared by thermal decomposition method. The SASR approach described in this paper represents a new blueprint for the generation of the supported alkali oxide as the solid base catalyst.

A new family of anionic organic-inorganic hybrid doughnut-like nanostructures.

A family of soluble organic-inorganic hybrid doughnut-like anions, hydoughnuts, has been prepared by the self-assembly of polyoxovanadate anions and 1,3-benzenedicarboxylate (bdc) linkers. Derivatives of the parent hydoughnut, [(V4O8Cl)4(bdc)8](4-), can be obtained by changing the counter-ion or by using a variant of bdc.

A calixarene based metal organic material, calixMOM, that binds potassium cations.

A porous calixarene-based metal organic material, calixMOM-1, has been prepared by using a custom designed tetradentate thiacalixarene which links manganese molecular building blocks. Potassium ions were introduced into the cavity of the thiacalixarene to afford calixMOM-2. Gas sorption properties of both compounds were studied.

Two homochiral organocatalytic metal organic materials with nanoscopic channels.

Two homochiral organocatalytic MOMs were prepared using tetra- and octa-carboxylate ligands, respectively. The nanoscopic channels in these MOMs are lined by organonocatalytic chiral phosphoric acid derivatives of binol and ocMOM-1 exhibited improved enantioselectivity over the parent ligand in the context of transfer hydrogenation of a series of benzoxazines.

A new MOF-505 analog exhibiting high acetylene storage.

A new microporous metal-organic framework Cu(2)(EBTC)(H(2)O)(2) x xG (EBTC = 1,1'-ethynebenzene-3,3',5,5'-tetracarboxylate; G = guest molecule) was rationally designed with a NbO net, exhibiting significantly high acetylene storage of 252 and 160 cm(3) g(-1) at 273 and 295 K under 1 bar, respectively.