Search

In this study, a novel mixed‐matrix membrane (MMM) based on covalent incorporation of poly(styrene‐alt‐maleic anhydride) (PSMA) with a metal‐organic framework (MOF) UiO‐66‐NH2 was prepared and utilized for dye removal from aqueous solution. The fabrication of PSMA and UiO‐66‐NH2 was carried out by the amidation reaction between the maleic anhydride ring and amino functional group affording crosslinked MOF/PSMA membrane. The separate UiO‐66‐NH2 and PSMA solutions were mixed before cast films were produced. The MMM was prepared with final UiO‐66‐NH2 wt % content from 0 to 30 % in each membrane. The formation of MMM was confirmed with FT‐IR, PXRD, TGA, SEM, and XPS analysis. The MMM having high adsorption capacity was used for the separation of methylene blue (MB) and methyl orange (MO) as organic dye pollutants commonly found in wastewater. The MMM could be recycled and still maintained 75 and 52 % retention of MB and MO on the third reuse cycle, respectively. The results suggest that the MOF incorporated PSMA was an outstanding membrane for the development of filtration techniques for decontamination of water resources. [ABSTRACT FROM AUTHOR]

[Display omitted] • Aminobenzoate-defected UiO-66(Zr)–NH 2 was produced by continuous-flow synthesis. • Defective AUiO-66-NH 3 + exhibited enhanced adsorption capacity for NCCs in n -octane. • AUiO-66-NH 3 + pellets treated NCCs effectively under continuous fixed-bed conditions. • The adsorption mechanisms of NCCs onto the adsorbents were revealed. In this work, imperfection UiO-66-NH 2 frameworks (AUiO-66-NH 2) were engineered and scalably produced by a continuous flow method with the assistance of 4-aminobenzoate (ABA) modulators. ABA modulators competed with MOF ligands to bond to Zr4+ clusters under continuous flow conditions, producing AUiO-66-NH 2 frameworks containing aminobenzoate linkers and ligand-missing defects. The average ligand deficiency per Zr 6 unit of defective AUiO-66(Zr)–NH 2 framework ranged from 0.75 ∼ 2.36 upon changing ABA/H 2 N-BDC molar ratio and reaction temperature, thereby adjusting their porosity and exposing more metal open sites of Zr4+. The batch removal of N-containing compounds (NCCs), including quinoline (QUN) and 2-methyl pyrrole (MPR) in n -octane indicated that the ABA-modulated UiO-66-NH 2 samples had improved adsorption capability compared to the perfect MOF. Noticeably, the adsorption performances were further enhanced by protonating 2.5AUiO-66-NH 2 to 2.5AUiO-66-NH 3 + owing to the synergetic effects of acid-base interaction, H-bonds, cation-π interactions, and π-π stacking interactions between adsorbent and adsorbate. Density functional theory (DFT) calculations further revealed that the NCCs preferably accumulated onto the protonated AUiO-66-NH 3 + rather than AUiO-66-NH 2. The AUiO-66-NH 3 + exhibited adsorbing capacities of ∼204 mg/g and ∼275 mg/g for MPR and QUN, respectively, and obeyed the pseudo-second-order kinetic model. Finally, the continuous fixed-bed adsorptions of these NCCs in model fuel over the AUiO-66-NH 3 + pellets (3 mm × 6 mm) showed that 1.0 g of adsorbent can purify with ∼28 L and ∼49 L liquid fuel containing MPR and QUN with a concentration of 1 mg L−1. These state that combining continuous-flow synthesis and defect engineering of the UiO-66-NH 2 could be a promising strategy to produce efficient adsorbent materials for upgrading liquid fuel. [ABSTRACT FROM AUTHOR]

The development of π-complexation adsorbents with Cu(I) having high CO adsorption capacity, high selectivity, large working capacity, and good stability is still very challenging up to now. In this work, π-complexation adsorbent with Cu+ was fabricated by reducing Cu2+ to Cu+ within amino-functionalized MIL-101 (Cr) framework by employing formate (HCOO-) at low temperature. The obtained results indicated that the Cu+ yield was strongly influenced by the chelation of Cu(II) species into amino groups (NH 2) of MIL-101 (Cr)-NH 2. The produced CuCl@MIL-101(Cr)-NH 2 (CuCl@MCrN) was then applied for CO and CO 2 adsorption at various conditions. The results revealed that the formed Cu+ species within MIL-101 (Cr)-NH 2 not only increased CO adsorption via CO π-complexation but also reduced CO 2 adsorption on the adsorbent through interaction with NH 2 groups, resulting in a significant increase of CO/CO 2 selectivity onto CuCl@MCrN adsorbent. At 25 °C and 100 kPa, the prepared CuCl@MCrN adsorbent with 30% Cu(I) exhibited the maximum CO uptake amount and CO/CO 2 selectivity of ~ 2.52 mmol g−1 and ~ 97, respectively, exceeding those of the benchmark Cu+-based π-complexation adsorbents. The breakthrough experiment indicates that this Cu(I)@MIL-101(Cr)-NH 2 adsorbent can efficiently separate CO/CO 2 mixture under dynamic mixture flow conditions. Moreover, the oxygen-resistant ability of the adsorbent tested under atmospheric humidity conditions demonstrated that CuCl@MCrN adsorbent had good stability. [Display omitted] • Cu(I)-incorporated MIL-101(Cr) was effectively prepared by a facile approach. • Time-dependent reduction was optimized to achieve high Cu+ yield on MIL-101(Cr)-NH 2. • Cu-N chelation affected gas adsorption performance on CuCl@MCrN. • CuCl@MCrN adsorbent had high CO/CO 2 selectivity and CO working capacity. • The chelated Cu-N bonds improved the oxygen-resistant ability of the formed Cu+. [ABSTRACT FROM AUTHOR]

[Display omitted] • Defective UiO-66 was rapidly fabricated by continuous-flow microwave synthesis. • The surface area and pore width of UiO-66 (Zr) were improved by defects. • The most defective 25Cu(I)@UiO-66 had the highest CO uptake capacity of 2.44 mmol/g. • Defective Cu(I)@UiO exhibited improved CO selectivity. • Cu(I)@UiO-66(Zr) showed good renewability and oxygen-resistant ability. Developing a highly effective material for CO storage and separation is a challenge. In this study, we first used microwave-assisted continuous-flow synthesis to create defective UiO-66(Zr) frameworks with improved surface area and pore structures, which is highly efficient for large-scale production. The defect concentration of UiO-66(Zr) was rapidly and effectively controlled within a short reaction time of 10 min. Different amounts of Cu2+ were loaded onto defective UiO-66 samples, followed by reducing Cu2+ to Cu+ to obtain Cu(I)@UiO-66 adsorbents (Cu(I)@UiO). X-ray diffraction (XRD), N 2 -adsorption, FT-IR, SEM, TEM, thermogravimetric analysis (TGA), and XPS analyses were used to characterize the physicochemical properties of the prepared adsorbent materials. Gas adsorption experiments revealed that Cu(I)-decorated defective UiO-66 exhibited high CO adsorption capacity due to the π complexation between Cu+ and CO. The CO adsorbing amount and CO selectivity onto the Cu(I)@UiO-66 samples were improved by adjusting the defect concentration and Cu(I) load on the UiO-66 host. The breakthrough experiment confirms that this defective Cu(I)@UiO adsorbent can efficiently separate CO/N 2 mixture under dynamic mixture flow conditions. Furthermore, after several cyclic adsorption–desorption experiments, the defective Cu(I)@UiO-66 is highly regenerable and has a good oxygen-resistant ability. The study describes a simple and scalable method for producing π-complexation adsorbent for CO adsorption. [ABSTRACT FROM AUTHOR]

• Amino-defective UiO-66 was prepared in a one-step synthesis process using 4-amino benzoic acid. • Adding 4-aminobenzoic acid enhanced the porosity and formation of amino groups as new CO 2 adsorption sites. • The defect degree was controlled by 4-aminobenzoic acid concentration. • Amino-defective UiO-66 showed improved CO 2 adsorption capacity and CO 2 /N 2 selectivity. UiO-66(Zr), one of the Zr-based metal–organic frameworks (MOFs), is a potential adsorbent for gas separation owing to its large surface area, easily tunable pore structure, and high chemical/thermal stability. Nevertheless, its CO 2 adsorption amount is somewhat modest in comparison to that of various MOFs. In this study, 4-aminobenzoic acid (PABA) as amino-defective linker was mixed to terephthalic acid at various compositions in a one-step synthesis of UiO-66(Zr) framework. This new restructuring strategy produced defective UiO-66(Zr) with enhanced porosity owing to the missing-linker defects, simultaneously formed –NH 2 groups in the framework, leading to the improvement of the CO 2 capture capacity. At 298 K and 100 kPa, the defective UiO-66 modified with 10% PABA exhibited the highest CO 2 uptake capacity of ~ 2.47 mmol g−1 and ideal adsorbed solution theory (IAST)-based CO 2 /N 2 selectivity of ~ 46, which surpass many other CO 2 benchmark adsorbents. This opens a new perspective for developing defective UiO-66(Zr) adsorbent contained amine functional groups, which can improve CO 2 separation performance. [ABSTRACT FROM AUTHOR]

In this study, we developed a facile and scalable preparation method of CuCl@γ-Al 2 O 3 composite microspheres for CO storage and separation by combining sol-gel and spray pyrolysis methods, followed by metal salt impregnation. γ-Al 2 O 3 microspheres were first prepared by spray pyrolysis of a mixture containing various ratios of boehmite sol and citric acid (CA). Pore-size distribution analyses indicated that the mesopores that are generated inside of the γ-Al 2 O 3 microspheres and their pore volumes could be fine-tuned by adjusting the CA/boehmite ratio. Importantly, the newly formed pore structures have been identified to accelerate the thermal dispersion of CuCl species into the γ-Al 2 O 3 matrix, resulting in improved CO sorption. Gas-adsorption experiments showed that CO-adsorption capacity and CO/CO 2 selectivity were strongly affected by the CA/boehmite ratio, CuCl-dispersion temperature, and CuCl-loading amount. The optimized adsorbent exhibited a maximum CO-adsorption capacity of 1.69 mmol g−1 and CO/CO 2 selectivity of 84 (at 25 °C and 100 kPa), exceeding the benchmarks for CO-selective adsorbents. Moreover, the spherical CuCl@γ-Al 2 O 3 adsorbent showed good regenerative ability after a number of adsorption–desorption cycles. This study provided facile and scalable synthesis method for low-cost CO-selective material with high CO performance. [Display omitted] • Spray pyrolysis –derived CuCl@γ-Al 2 O 3 composite microspheres were simply fabricated. • Citric acid/boehmite, pyrolysis temperature, and CuCl amount were optimized. • High dispersion of CuCl was achieved by improving the pore structures of γ-Al 2 O 3. • CuCl@γ-Al 2 O 3 has exhibited high CO/CO 2 selectivity and CO-uptake and working capacity. • The CuCl@γ-Al 2 O 3 adsorbent demonstrated good regenerative ability. [ABSTRACT FROM AUTHOR]

• Bimetallic CuFe-incorporated MIL-101(Cr) was prepared by a double-solvent route. • The yield and dispersion of the Cu(I) sites in the host were improved by Fe(II) sites. • CuFe@MCr exhibited the best CO-adsorption performance among the MIL-101(Cr), Cu@MCr, and CuFe@MCr-IM adsorbents. • CuFe@MCr exhibited superior oxygen-resistant stability. In this study, a bimetallic CuFe-incorporated MIL-101(Cr) adsorbent was developed with enhanced CO-adsorption capacity and oxygen resistance. Different compositions of bimetallic Cu(II)–Fe(II) were incorporated into the MIL-101(Cr) framework with ultrahigh porosity by the double-solvent (DS) method, followed by facile reduction at a low temperature of 250 °C. By employing formate (HCOO−), Cu(II) was selectively reduced to Cu(I) at 250 °C. Moreover, the presence of the reducing agent, Fe(II), enhanced the reduction of Cu(II) in the adsorbent. The obtained results indicated that the synergistic effect of utilizing Fe(II) and employing the DS method significantly enhanced the dispersion of the formed Cu(I) in the support. The DS-assisted CuFe (4 mmol g−1 of CuCl and 1.0 mmol g−1 FeCl 2)-incorporated MIL-100(Fe) adsorbent exhibited a high CO-adsorption capacity of ca. 3.24 mmol g−1 and CO/N 2 selectivity of 428 at 25 °C and 100 kPa, which were superior to those of the counterpart that was prepared by the wetness impregnation method. Additionally, the CO-adsorption capacity of the prepared CuFe-incorporated MIL-100(Fe) was still 90–65% after it was exposed to atmospheric humidity for 15–30 days, thereby demonstrating its superior oxygen-resistant stability compared to those of the benchmark π-complexation adsorbents containing Cu(I). [ABSTRACT FROM AUTHOR]

Defect engineering is a promising approach for tailoring the physicochemical properties, such as stability, pore structure, and surface area, of metal–organic frameworks (MOFs). In this study, some defective Zr-based biphenyl dicarboxylate (UiO-67 (Zr)) MOFs were prepared via fast modulated synthesis under microwave-assisted continuous flow by using HCOOH, CH 3 COOH, CH 3 CH 2 COOH, and C 6 H 5 COOH as modulators. A surface-modified UiO-67(Zr) framework with high porosity and crystallinity could be rapidly produced in a few minutes due to the incomplete exchange between the bridging ligand and the modulator. The defect concentration in the products was tuned by controlling both the modulator species and concentrations utilized. The adsorption ability toward toluene of the prepared UiO-67(Zr) MOFs was found to be related to their structural defects; the defective UiO-67(Zr) MOF synthesized with HCOOH as the modulator exhibited the highest toluene adsorption capacity (467 mg g−1), surpassing also most of the previously reported adsorbent materials, such as zeolites, activated carbon, Zr-based dicarboxybenzene (UiO-66(Zr)), H 2 N-UiO-66(Zr), zeolitic imidazolates, and copper benzenetricarboxylate. Moreover, the experimental dynamic adsorption data were mathematically modeled to predict the adsorption behaviors of defective UiO-67(Zr) MOFs. Image 1 • Defective UiO-67(Zr) was rapidly produced under microwave-assisted continuous flow. • UiO-67(Zr) defects were tunable by the modulator species and concentration. • UiO-67(Zr) structural defects influenced the toluene adsorption ability. • The highest toluene adsorption capacity obtained was 467 mg g−1. • The toluene dynamic adsorption was mathematically modeled. [ABSTRACT FROM AUTHOR]

In this work, different contents of 1-butyl-3-methylimidazoliumbromide ionic liquid (IL) were entrapped into amino-functionalized MIL-101(Cr) frameworks using the ship-in-a-bottle strategy to harvest novel adsorbent, namely C 4 mim@MIL-101(Cr)-NH 2 [C 4 mim@MCr-NH 2 ]. The prepared materials were characterized and exploited for phosphate removal using batch and continuous fixed-bed adsorption modes. In batch adsorption, the optimized C 4 mim@MCr-NH 2 containing 9 wt% IL had the highest phosphate absorbing capacity of ∼ 240 mg/L at pH media ∼ 4.5, exceeding the pristine MIL-101-NH 2 (∼ 91 mg/g) thanks to the synergetic effects resulting from adding adsorption sites of ILs and protonating -NH 2 groups. The phosphate capture onto the C 4 mim@MCr-NH 2 adsorbents obeyed the pseudo-second-order model, and the procedure was predominantly monitored by hydrogen bonds, electrostatic interactions, and π-cation interactions. The phosphate treatment under continuous fixed-bed conditions using PVA(4%)-mixed C 4 mim@MCr-NH 2 pellets (∼ 3×5 mm) was described by Thomas' and Yan's column models, which showed that 1 g of the adsorbent could treat ∼26.4 L of water containing phosphate contaminant with 1 mg/L concentration. Overall, the harvested [C 4 mim]+[Br]--entrapped MIL-101(Cr)-NH 2 showed a good ADP performance, making it a promising adsorbent for controlling phosphate in water. [Display omitted] • [C 4 mim]+[Br]--entrapped MIL-101(Cr)-NH 2 prepared using a ship-in-a-bottle approach. • IL@MCr-NH 2 achieved a phosphate adsorption capacity of ∼240 mg/g. • The kinetic and mechanism of phosphate adsorption onto the adsorbents were revealed. • IL@MCr-NH 2 pellets effectively treated phosphate under continuous fixed-bed conditions. [ABSTRACT FROM AUTHOR]

Metal-organic frameworks (MOFs) are typically synthesized in closed batch systems, which is not favorable for large scale production. Herein, we report a scalable MOF synthesis route based on a continuous flow tubular reactor equipped with microwave volumetric heating. The system enabled continuous crystallization of MIL-100(Fe) with a high space time yield of ~771.6 kg/m3/day under relatively mild conditions (temperature: 100–110 °C and time: 50 min). Ultimately, the MIL-100(Fe) was used as a support to prepare Cu(I)-modified π complexation adsorbents. The adsorbents exhibited preferred CO adsorption over CO 2 , and the adsorption performance (CO adsorption capacity and CO/CO 2 selectivity) was comparable to, or even higher than most of the previously reported Cu(I)-modified π complexation adsorbents. Image 1 • MIL-100(Fe) was continuously synthesized in a microwave-assisted flow reactor. • MIL-100(Fe) was used as a support to make Cu(I)-modified π complexation adsorbents. • The adsorbents exhibited preferred CO adsorption over CO 2. [ABSTRACT FROM AUTHOR]