Hypercrosslinked silole‐containing microporous organic polymers with N‐functionalized pore surfaces for gas storage and separation

Novel hypercrosslinked microporous organic polymers (MOPs) derived from N‐functionalized siloles as basic building units have been designed and synthesized via Friedel–Crafts alkylation reaction. The resulting N‐functional silole‐containing polymer networks exhibit high thermal stabilities and moderate Brunauer–Emmett–Teller surface area ranging from 666 to 1137 m² g^?1. The incorporation of carbazole or triphenylamine moieties into the polymer skeleton increases the number of electron donating basic nitrogen sites in the porous frameworks. Thus, the corresponding polymer PDMCzS shows enhanced CO₂ adsorption capacities of 3.23 mmol g^?1 at 273 K and 1.13 bar, and higher CO₂/N₂ selectivity (43.99) at 273 K than the analogous silole‐containing polymers P1–P3. These results demonstrated that the N‐functionalized silole‐containing polymer network is a very promising candidate for potential applications in post‐combustion CO₂ capture and sequestration. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45907.     

Functionalized metal‐organic polyhedra hybrid membranes for aromatic hydrocarbons recovery

Pervaporation membranes are potentially useful in the separation of aromatic/aliphatic mixtures. Wherein, the membrane material plays a key role. Herein, a series of functionalized metal‐organic polyhedra (MOPs)/hyperbranched polymer hybrid membranes are molecularly designed and fabricated for the recovery of aromatic hydrocarbons. The isostructural MOP molecules with different functional groups are uniform in shape/size and soluble in solvents, which enable them to disperse well and be compatible in/with the polymer. Pervaporation results demonstrated significant improvements of these membranes in separation performances. Particularly, the membrane with MOP‐SO₃Na_nH_m showed the separation factor of 8.03 and the permeation flux of 528 g/m²h for the recovery of toluene from its 50 wt % n‐heptane mixture, and those values are 8.4 and 540 g/m²h for benzene/cyclohexane mixture. We propose that the selectivity of these membranes is affected primarily by the polarity of functional groups in MOPs, which were further explained by the adsorption experiments and molecular simulations. © 2016 American Institute of Chemical Engineers AIChE J, 62: 3706–3716, 2016     

Dense open metal sites in a microporous metal–organic framework for deep desulfurization with record-high sulfur dioxide storage density

Dry desulfurization employing porous adsorbents is industrially preferred but efficient capture of sulfur dioxide (SO₂) at the ultralow concentration (i.e., 2000 ppm) is exceptionally challenging. Metal–organic frameworks with open metal sites (OMSs) can provide sufficient interactions with SO₂, which, in turn, will degrade or compromise the structural robustness. Herein, we reported Cu-ATC that contains dense oppositely positioned Cu OMSs for efficient trace SO₂ removal. Explicitly, Cu-ATC adsorbs a benchmark amount of SO₂ (5.3 mmol g⁻¹) at 0.01 bar with a record-high SO₂ storage density of 2.23 g cm⁻³ at ambient conditions. The critical role of OMSs has been confirmed by the partially desolvated sample with declined uptakes and adsorption enthalpy. The desulfurization performances have been validated by multicycle breakthrough experiments even with mimic flue-gas and water vapor. Computational simulations identify the adsorption sites at the molecular level. Combined with the high stability under various conditions, Cu-ATC is a potent candidate for industrial implementation.     

Improving iodine adsorption performance of porous organic polymers by rational decoration with nitrogen heterocycle

Four kinds of porous aminal-linked organic polymers (PAOPs) were synthesized via one-step condensation between cheap melamine and respective aldehydes decorated with different nitrogen heterocycle, to evaluate the influence of nitrogen heterocycle on the adsorption performance of target polymer toward iodine. Though having the smallest surface area of 209.9 m²/g, PAOP-4 decorated with pyridine group exhibits an adsorption capacity of 108 wt% (iodine/adsorbent weight%), surpassing other three PAOPs with Brunauer–Emmett–Teller area varying from 305.8 to 533.0 m²/g. Based on Raman spectral analyses, the characteristic band of I₃⁻ and I₅⁻ was used to evaluate the electronic interaction between iodine and the nitrogen heterocycle, giving an order of pyridine > tetrazole > pyrazole > imidazole. This manifests the vital role of chemical interaction playing in the iodine adsorption by PAOP-4, which is much helpful for designing high-performance organic adsorbent toward iodine.     

Fabrication of PEI-grafted porous polymer foam for CO2 capture

A polymer foam material with both the open-cell porous structure and the polyethylenemine (PEI)-grafted inner face was constructed for CO₂ capture. The porous poly(tert-butyl acrylate) foam was first prepared via a concentrated emulsion polymerization, and then the carboxyl groups were introduced on the interface of porous polymer after the hydrolysis reaction. Subsequently, the surface of the foam was grafted with PEI, and finally the PEI-grafted porous polymer foam designed as a CO₂ capture material was obtained. The structures of the foams were characterized by infrared spectroscopy, EDS, and SEM. The CO₂ adsorption properties were measured by adsorption/desorption cycles. As a result, the polymer foam contained a large number of amine groups (13.9 wt % N), and therefore possessed a high CO₂ adsorption capacity (5.91 mmol g⁻¹ at 40°C and 100 kPa). In addition, they also exhibited high CO₂ adsorption rate, good selectivity for CO₂-N₂ separation, and good stability according to CO₂ cyclic adsorption/desorption test. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47844.     

Novel sulfonated multi-walled carbon nanotubes filled chitosan composite membrane for fuel-cell applications

In the present study, multi-walled carbon nanotubes (MWCNTs) were sulfonated by 1,3-propane sultone and distillation–precipitation polymerization, respectively, and then incorporated into chitosan (CS) to prepare CS/MWCNTs composite membranes for fuel cell applications. CS/MWCNTs membranes show better thermal and mechanical stability than pure CS membrane due to the strong electrostatic interaction between the  SO₃H groups of MWCNTs and the  NH₂ groups of CS, which can restrict the mobility of CS chain. The sulfonated MWCNTs provide efficient proton hopping sites ( SO₃H,  SO₃⁻ …. ₃⁺HN ), thereby resulting in the formation of continuous proton conducting channels. The composite membranes with 5 wt % of MWCNTs modified by two different ways show a proton conductivity of 0.026 and 0.025 S·cm⁻¹, respectively. In conclusion, CS/MWCNTs membrane is a promising proton exchange membrane for fuel-cell applications. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47603.     

Hierarchical porous carbon obtained from animal bone and evaluation in electric double-layer capacitors

Animal bone, an abundant biomass source and high volume food waste, had been converted into a hierarchical porous carbon in a simple two-step sustainable manner to yield a highly textured material. The structures were characterized by nitrogen sorption at 77 K, scanning electron microscopy and X-ray diffraction. The electrochemical measurement in 7 M KOH electrolyte showed that the porous carbon had excellent capacitive performances, which can be attributed to the unique hierarchical porous structure (abundant micropores with the size of 0.5–0.8 and 1–2 nm, mesopores and macropores with the size of 2–10 and 10–100 nm), high surface area (S_BET = 2157 m²/g) and high total pore volume (V_t = 2.26 cm³/g). Its specific capacitance was 185 F/g at a current density of 0.05 A/g. Of special interest was the fact that the porous carbon still maintained 130 F/g even at a high current density of 100 A/g.     

The efficient removal of organic pollutant over magnetic mesoporous polymer

Nanoporous polymers due to their abundant pores and organic frameworks are very suitable for the adsorption of organic pollutants in aqueous solution. However, the difficulty in separation and recovery limit their widely practical applications. Herein, polydivinylbenzene was first synthesized by solvothermal method, then magnetic Fe₃O₄ precursors were incorporated into the polymer framework to obtain magnetic polydivinylbenzene, designated as Fe₃O₄/PDVB. The as-prepared magnetic mesoporous polymer possessed rich porous structure, high specific area of 444.7 m²/g, pore size of 8.9 nm and pore volume of 0.82 cm³/g, which were fully verified by various characterization techniques. Noticeably, Fe₃O₄/PDVB showed efficient and fast adsorption rate to dye Rhodamine B, and the adsorption capacity reached 85.81 mg/g within 15 min. Moreover, the magnetic polymer can be easily separated by external magnetic field after adsorption and facilely recovered by ethanol extraction, which benefit its large-scale applications in the environmental protection, especially in the chemical accident remediation.     

Fine-tuning of phase behavior of oxazoline copolymer-based organic–inorganic hybrids as solid-supported sol–gel materials

Silica-supported organic–inorganic polymer hybrids were synthesized via in situ sol–gel condensation of silica monomer in the presence of oxazoline copolymer. A stable copolymer of 2-ethyl-2-oxaoline and 2-isopropyl-2-oxazoline was prepared using methyl p-tosylate as the living polymerization initiator with molecular mass of 4200 g mol⁻¹. Lower critical solution temperature (LCST) of this copolymer was thermally found to be at 77 °C. The copolymer was mixed with tetramethoxysilane (TMOS) in different amounts (0.039:1 to 0.158:1 weight ratios) via in situ sol–gel condensation to produce organic–inorganic hybrids including thermosensitive copolymer. Tuning of these solid-supported materials showed sharp phase transitions changes in a temperature range from 42 to 58 °C, which was confirmed using differential scanning calorimetry. Enthalpy of the phase transition was also calculated using the area above the endothermic peak. A typical concave curve was obtained for LCST-type phase diagram suggesting the dependence of phase transition temperature on the concentration of the copolymer in the hybrid. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48163.     

Synthesis of mesoporous carbon spheres with a hierarchical pore structure for the electrochemical double-layer capacitor

Mesoporous carbon spheres with hierarchical foam-like pore structures have been synthesized by a dual-templating strategy using phenolic resol as a carbon source, Pluronic F127 and spherical silica mesocellular foams (Si-MCFs) as the soft and hard template, respectively. The results show that the morphology and mesostructure of the silica template are faithfully replicated. The obtained mesoporous carbon material with spherical diameter size of ca. 3–5 μm exhibits hierarchical pore sizes (from ca. 3.5 to 60 nm), high specific surface area (1320 m²/g) and large pore volume (3.5 cm³/g). The carbon surface contains plenty of oxygen-containing groups, resulting in hydrophilic property for an electrode material. In addition, Pluronic F127 plays an important role in the synthesis for maintaining the foam-like mesostructure of the silica templates and faithful replication of the spherical morphology. The electrochemical measurements show that the hierarchically mesoporous carbon spheres as an electrochemical double-layer capacitor (EDLC) electrode present a long cyclic life, excellent rate capability, and high specific capacitance as ca. 208 F/g at 0.5 A/g in (2.0 M) H₂SO₄ aqueous solution. Its specific capacitance can still remain ca. 146 F/g at a high loading current density of 30 A/g with the retention of ca. 70%. Furthermore, this material also exhibits excellent capacitive performance in (C₂H₅)₄NBF₄/propylene carbonate electrolyte, and its specific capacitance is 97 F/g at loading current density of 0.5 A/g.     

Polycondensation of tetramethyldisiloxane 1,3-diol catalyzed by trifluoromethanesulfonic acid

The kinetics of polycondensation of tetramethyldisiloxane 1,3-diol (HD₂OH) have been followed by stopping the reaction at increasing times (by neutralization of the acid and trimethylsilylation of the silanol end-groups). Analyses of the linear and cyclic oligomers and of the higher polymer have been made by gas–liquid chromatography and by steric exclusion chromatography. At the beginning of the reaction (e. g. between 1 min and 1 h) the main products are linear oligomer H(D)_2nOH and D₄ (formed by cyclization of HD₄OH). There are only very small amounts of large cycles. Linear high polymer is then formed slowly together with increasing amounts of cycles D₅, D₆, D₇, …, formed by backbiting reactions. After 24h, the yield of D₄ is 40–50% and that of linear polymer 40–30% (M_peak × 10⁴–10⁵). With disilanol concentration 0.45–0.9 mol liter^?1 and CF₃SO₃H concentration about 10^?3 mol liter^?1, the reaction is very rapid during 1–2 min and the medium becomes heterogenous with the formation of an inverse water emulsion. The reaction then slows down considerably, most of the hydrated acid being trapped in the water droplets. Silanol consumption is second order in [SiOH] and first order [TfOH]_o. Polymerizations made in polar and non-polar solvents have similar rates, which however increase moderately in the order toluene<1,2-dichloro-ethane<dichloromethane, this corresponding to an increasing solubility of the hydrated acid in these solvents. Polycondensation occurs in the organic phase near the interface, either by esterification of silanol followed by heterccondensation or by homocondensation catalyzed by the hydrated acid (or both).     

Performance of a UV‐assisted Hydrogen‐peroxide‐fed Spray Tower for Sulfur Dioxide Abatement

Spray towers are widely used for controlling air pollution by gases such as SO₂, CO₂, NO_x, and HCl. Results of sulfur dioxide absorption in a spray tower using solutions of 1 g L^–1 and 2 g L^–1 of hydrogen peroxide are reported. For comparison, a water and sodium hydroxide solution was also used for SO₂ abatement. The results indicate that H₂O₂ may be an important alternative for SO₂ removal in spray towers. A set of experimental removal efficiency data was obtained as a function of gas and liquid flow rates. Volumetric mass transfer coefficients (k_ga) were calculated and an experimental relationship among k_ga, gas, and liquid flow rates was proposed. As a final experiment, an oxidation process assisted by UV radiation using a 1 g L^–1 solution of H₂O₂ was carried out to speed up the SO₂ removal rate. The results obtained in this condition are similar to those achieved with a solution of 2 g L^–1 H₂O₂.     

Synthesis of hierarchically porous mullite ceramics with improved thermal insulation via foam-gelcasting combined with pore former addition

ABSTRACT

To further improve the thermal insulation performance of porous mullite ceramics used in important industrial sectors, a combined foam-gelcasting and pore-former addition approach was investigated in this work, by which hierarchical porous mullite ceramics with excellent properties, in particular, thermal insulation property, were prepared. Both mesopores (2–50?nm) and macropores (117.8–202.7?μm) were formed in porous mullite ceramics resultant from 2?h firing at 1300°C with various amounts of submicron-sized CaCO₃ pore former. The former mainly arose from the decomposition of CaCO₃, and the latter from the foam-gelcasting process. The porous samples prepared with CaCO₃ addition had low linear shrinkage of 2.35–4.83%, high porosity of 72.98–79.07% and high compressive strength of 5.52–14.82?MPa. Most importantly, they also exhibited a very low thermal-conductivity, e.g. 0.114?W?m^?1?K^?1 at 200°C, which was much lower than in the cases of their counterparts prepared via the conventional foam-gelcasting route.     

Catalytic dehydration of glucose to 5‐hydroxymethylfurfural with a bifunctional metal‐organic framework

Glucose conversion to 5‐hydroxymethylfurfural (HMF) generally undergoes catalytic isomerization reaction by Lewis acids followed by the catalytical dehydration to HMF with Brönsted acid. In this work, a sulfonic acid functionalized metal‐organic framework MIL‐101(Cr)‐SO₃H containing both Lewis acid and Brönsted acid sites, was examined as the catalyst for γ‐valerolactone‐mediated cascade reaction of glucose dehydration into HMF. Under the optimal reaction conditions, the batch heterogeneous reaction gave a HMF yield of 44.9% and selectivity of 45.8%. Reaction kinetics suggested that the glucose isomerization in GVL with 10 wt % water follows the second‐order kinetics with an apparent activation energy of 100.9 kJ mol^?1. Continuous reaction in the fixed‐bed reactor showed that the catalyst is highly stable and able to provide a steady HMF yield. This work presents a sustainable and green process for catalytic dehydration of biomass‐derived carbohydrate to HMF with a bifunctional metal‐organic framework. © 2016 American Institute of Chemical Engineers AIChE J, 62: 4403–4417, 2016     

Preparation of a magnetic chitosan composite adsorbent by ammonia fumigation

A magnetic chitosan (CS) composite material was synthesized successfully by a new procedure, ammonia fumigation, which is suitable for large‐scale production. CS dissolved in an aqueous acetic acid solution was mixed with [Fe(SO₄)₂]^2? and [Fe(SO₄)₂]^? ions to obtain a light yellow precipitate, which was then exposed to ammonia vapor to prepare the composite adsorbent product. The microstructure of the composite was studied by scanning electron microscopy, transmission electron microscopy, X‐ray diffraction, and Fourier transform infrared spectroscopy. The results indicate that Fe₃O₄ particles 3–7 nm in size were formed in situ and were stabilized in the CS matrix. The composite adsorbent showed superparamagnetic properties with a saturation magnetization of about 11.0 emu/g. Moreover, the composite material displayed good adsorption of methyl orange and copper ions. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40057.     

A redox poly(ionic liquid) hydrogel: Facile method of synthesis and electrochemical sensing

In this article, a redox-responsive poly(ionic liquid) (redox-PIL) hydrogel Poly(1-vinyl-3-propionate imidazole phenothiazine sulfonic acid)-chitosan [Poly(VPI⁺PTZ-(CH₂)₃SO₃⁻)-CS] was produced by using chitosan (CS) crosslinking with redox-PIL Poly(1-vinyl-3-propionate imidazole phenothiazine sulfonic acid [Poly(VPI⁺PTZ-(CH₂)₃SO₃⁻)]. The incorporation of redox-active counter anions 3-(phenothiazine-10-yl) propane 1-sulfonic acid anions (PTZ-(CH₂)₃SO₃⁻) into cationic PIL-polyimidazole rendered Poly(VPI⁺PTZ-(CH₂)₃SO₃⁻) with electron catalytic ability, ionic conductivity, and electron conductivity. Poly(VPI⁺PTZ-(CH₂)₃SO₃⁻)-CS combines the properties of hydrogel and redox-PIL, thus offering intrinsic porous conducting frameworks and promoting the transport of charges, ions, and molecules, leading hydrogel with excellent electrochemical properties. The crosslinking occurrence of Poly(VPI⁺PTZ-(CH₂)₃SO₃⁻) and CS resulting from the synthetic process of hydrogel was verified by differential scanning calorimetry and thermogravimetric analysis. A three-dimensional polymer network hydrogel with good biocompatibility and permeability was formed after crosslinking. In addition, only 64% weight loss within 600 °C was observed in Poly(VPI⁺PTZ-(CH₂)₃SO₃⁻)-CS representing its thermally stable performance. When used as an electrochemical sensor, the hydrogel-modified gold electrode improved the electrocatalytic oxidation of cysteine. Differential pulse voltammetry results indicated that the detection range was from 5 × 10⁻⁸ to 5 × 10⁻³ M and the limit of detection was 6.64 × 10⁻⁸ M. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48051.     

Effect of silicone dioxide and poly(ethylene glycol) on the conductivity and relaxation dynamics of poly(ethylene oxide)–silver triflate solid polymer electrolyte

The conducting and relaxation dynamics of Ag⁺ ions in poly(ethylene oxide) (PEO)–silver triflate (AgCF₃SO₃) solid polymer electrolytes (SPEs) containing nanosize SiO₂ filler and poly(ethylene glycol) (PEG) as a plasticizer were studied in the frequency range 10 Hz to 10 MHz and in the temperature range 303–328 K. The comparatively lower conductivity of the plasticized (PEG) PEO–AgCF₃SO₃–SiO₂ nanocomposite electrolyte system was examined by analysis of the Fourier transform infrared (FTIR) spectroscopy and conductivity data. The electric modulus (M″) properties of the SPE systems were investigated. A shift of the M″ peak spectra with frequency was found to depend on the translation ion dynamics and the conductivity relaxation of the mobile ions. The value of the conductivity relaxation time was observed to be lower for the PEO–AgCF₃SO₃ system only with nanofiller SiO₂. The scaling behavior of the M″ spectra showed that the dynamical relaxation processes was temperature-independent in the PEO–AgCF₃SO₃ and PEO–AgCF₃SO₃–SiO₂–PEG polymer systems, whereas they were temperature-dependent for the PEO–AgCF₃SO₃–SiO₂ system. However, the relaxation processes of all of theses systems were found to be dependent on their respective compositions. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Effect of different acids during the synthesis of urea-formaldehyde adhesives and the mechanical properties of medium-density fiberboards bonded with them

The characteristics of urea-formaldehyde (UF) adhesives condensed by catalysis with four different acids, namely formic (HCOOH), hydrochloric (HCl), phosphoric (H₃PO₄), and sulfuric (H₂SO₄) acids, under alkaline–acidic–alkaline conditions at a molar ratio F/U = 1.12 were studied. The thermal curing properties of UF adhesives catalyzed with acid were characterized by differential scanning calorimetry at 10 °C/min heating rate. The resin structure examined by ¹³C-NMR spectroscopy showed that the resin catalyzed with HCl had a lower proportion of methylol groups, resulting in a lower level of formaldehyde emission. It was interesting to note that HCOOH resulted in the best overall mechanical properties of the medium-density fiberboard (MDF) panels. The HCl catalyst resulted in the poorest performance, providing the lowest internal bond strength, modulus of elasticity, and thickness swelling, with the exception of the free formaldehyde content. The resin catalyzed with H₂SO₄ had the highest free formaldehyde and the highest formaldehyde emission. H₂SO₄ and H₃PO₄ resulted in MDF mechanical properties relatively lower than for HCOOH. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47256.     

Template‐Free Synthesis of Porous Fe3O4/SiOC(H) Nanocomposites with Enhanced Catalytic Activity

We present a template‐free synthesis of Fe₃O₄/SiOC(H) nanocomposites with in situ formed Fe₃O₄ nanoparticles with a size of about 50 nm embedded in a nanoporous SiOC(H) matrix obtained via a polymer‐derived ceramic route. Firstly, a single‐source precursor (SSP) was synthesized by the reaction of allylhydridopolycarbosilane (AHPCS) with Fe‐acetylacetonate [Fe(acac)₃] at 140°C. The SSP was heat‐treated at 170°C to generate Fe₃O₄ nanocrystals in the cross‐linked polymeric matrix. Subsequently, the SSP was pyrolyzed at 600°C–700°C in argon atmosphere to yield porous Fe₃O₄/SiOC(H) nanocomposites with the high BET surface area up to 390 m²/g, a high micropore surface area of 301 m²/g, and a high micropore volume of 0.142 cm³/g. The Fe‐free SiOC(H) ceramic matrix derived from original AHPCS is nonporous. The in situ formation of Fe₃O₄ nanoparticles embedded homogeneously within a nanoporous SiOC(H) matrix shows significantly enhanced catalytic degradation of xylene orange in aqueous solution with H₂O₂ as oxidant as compared with pure commercial Fe₃O₄ nanoparticles.     

Polymer miscibility in organic solvents and in plasticizers—a two-dimensional approach

From thermodynamic considerations based on associated solution models and from the Hansen's three-dimensional solubility parameter concept, it is found that the solvent power of an organic liquid for a given polymer can be characterized by two parameters, δ_h and χ_H, where δ_h is the hydrogen-bonding solubility parameter of the liquid, and χ_H is a term which takes account of the dispersion and polar interactions between the liquid and the polymer and of the effects due to temperature and molecular size of the liquid. It is also found that Hansen's solubility sphere for the polymer can be represented as a solubility circle in the proposed χ_H^?δ_h plane. The proposed approach is applied successfully to polymer–plasticizer systems.