Tunable Interlayer Shifting in Two-Dimensional Covalent Organic Frameworks Triggered by CO2 Sorption.

Two-dimensional covalent organic frameworks (2D COFs) have been widely viewed as rigid porous materials with smooth and reversible gas sorption isotherms. In the present study, we report an unusual hysteresis step in the CO2 adsorption isotherm of a 2D COF, TAPB-OMeTA. In situ powder X-ray diffraction (PXRD) measurements, computational modeling, and Pawley refinement indicate that TAPB-OMeTA experiences slight interlayer shifting during the CO2 adsorption process, resulting in a new structure that is similar but not identical to the AA stacking structure, namely, a quasi-AA stacking structure. This interlayer shifting is responsible for the step in its CO2 adsorption isotherm. We attribute the interlayer shifting to the interactions between COF and CO2, which weaken the attraction strength between adjacent COF layers. Notably, the repulsion force between the methoxy groups on the backbone of TAPB-OMeTA is essential in facilitating the interlayer shifting process. After further increasing the size of side groups by grafting poly(N-isopropylacrylamide) oligomers to the TAPB-OMeTA backbone via surface-initiated atom transfer radical polymerization (SI-ATRP), we observed a second interlayer shifting and two adsorption steps in the CO2 adsorption isotherm, suggesting tunability of the interlayer shifting process. Density functional theory (DFT) calculations confirm that the quasi-AA stacking structure is energetically preferred over AA stacking under a CO2 atmosphere. These findings demonstrate that 2D COFs can be "soft" porous materials when interacting with gases, providing new opportunities for 2D COFs in gas storage and separation.

One-Step Ethylene Purification from Ternary Mixtures in a Metal-Organic Framework with Customized Pore Chemistry and Shape.

Adsorptive separation is an energy-efficient technology for the separation of C2 hydrocarbons. However, it remains a critical problem to directly produce high-purity C2 H4 from ternary C2 H2 /C2 H4 /C2 H6 mixtures by simultaneously trapping C2 H2 and C2 H6 . Herein, we report the one-step C2 H4 purification from the ternary mixture by a metal-organic framework Zn(ad)(int) (ad=adeninate; int=isonicotinate). The material combines dense heterocyclic rings and accessible uncoordinated O atoms as strong binding sites for C2 H6 and C2 H2 . Its spindle-like cage exhibits an interesting shape matching with the targeted molecules, affording Zn(ad)(int) not only high separation selectivity for C2 H6 /C2 H4 and C2 H2 /C2 H4 , but also excellent gas capacity. Breakthrough experiments show that polymer-grade C2 H4 can be separated from the ternary mixtures with a record productivity of 1.43 mmol g-1 . In situ powder X-ray diffraction and Fourier transform infrared spectrum analyses further provide deep insights into the separation mechanism.

Tetrazole-Functionalized Zirconium Metal-Organic Cages for Efficient C2 H2 /C2 H4 and C2 H2 /CO2 Separations.

Isoreticular functionalization is a well-elucidated strategy for pore environment tuning and the basis of gas separation performance in extended frameworks. The extension of this approach to discrete porous molecules such as metal-organic cages (MOCs) is conceptually straightforward but hindered by synthetic complications, especially stability concerns. We report the successful isoreticular functionalization of a zirconium MOC with tetrazole moiety by bottom-up synthesis. The title compound (ZrT-1-tetrazol) shows promising C2 H2 /CO2 and C2 H2 /C2 H4 separation performance, as demonstrated by adsorption isotherms, breakthrough experiments, and density functional theory calculations. The design analogy between MOFs and highly stable MOCs may guide the synthesis of novel porous materials for challenging separation applications.

Optimal Pore Chemistry in an Ultramicroporous Metal-Organic Framework for Benchmark Inverse CO2 /C2 H2 Separation.

Isolation of CO2 from acetylene (C2 H2 ) via CO2 -selective sorbents is an energy-efficient technology for C2 H2 purification, but a strategic challenge due to their similar physicochemical properties. There is still no specific methodology for constructing sorbents that preferentially trap CO2 over C2 H2 . We report an effective strategy to construct optimal pore chemistry in a CeIV -based ultramicroporous metal-organic framework CeIV -MIL-140-4F, based on charge-transfer effects, for efficient inverse CO2 /C2 H2 separation. The ligand-to-metal cluster charge transfer is facilitated by CeIV with low-lying unoccupied 4f orbitals and electron-withdrawing F atoms functionalized tetrafluoroterephthalate, affording a perfect pore environment to match CO2 . The exceptional CO2 uptake (151.7 cm3 cm-3 ) along with remarkable separation selectivities (above 40) set a new benchmark for inverse CO2 /C2 H2 separation, which is verified via simulated and experimental breakthrough experiments. The unique CO2 recognition mechanism is further unveiled by in situ powder X-ray diffraction experiments, Fourier-transform infrared spectroscopy measurements, and molecular calculations.

Preparation, characterization, and separation mechanism of a dehydroabietic-acid-based shape-selective chromatographic stationary phase1.

Chromatographic stationary phases with molecular-shape selectivity are advantageous for the separation and analysis of geometric isomers. Herein, dehydroabietic acid is bonded on the surface of silica microspheres via 3-glycidoxypropyltrimethoxysilane to form a monolayer dehydroabietic-acid stationary phase (Si-DOMM) with a racket-shaped structure. Various characterization techniques indicate that Si-DOMM is successfully prepared, and the separation performance of a Si-DOMM column is evaluated. The stationary phase has a low silanol activity and metal contamination and a high hydrophobicity and shape selectivity. The resolutions of lycopene, lutein, and capsaicin on the Si-DOMM column confirm that the stationary phase exhibits high shape selectivity. The elution order of n-alkyl benzene on the Si-DOMM column indicates its high hydrophobic selectivity and suggests that the separation is an enthalpy-driven process. Repeatability experiments reveal highly stable preparation processes of the stationary phase and column and indicate that the relative standard deviations of retention time, peak height, and peak area are less than 0.26%, 3.54%, and 3.48%, respectively. Density functional theory calculations using n-alkylbenzenes, polycyclic aromatic hydrocarbons, amines, and phenols as model solutes provide an intuitive and quantitative description of the multiple retention mechanisms. The Si-DOMM stationary phase exhibits superior retention and high selectivity for these compounds via multiple interactions. The bonding phase of the monolayer dehydroabietic acid stationary phase with a racket-shaped structure has a unique affinity for benzene, strong shape selectivity, and good separation performance for geometrical isomers with different molecular shapes.

One-step ethylene purification from ternary mixtures by an ultramicroporous material with synergistic binding centers.

Developing advanced porous materials with industrial potential to separate multicomponent gas mixtures that are structurally similar is a crucial but challenging task. Here, we report the efficient one-step separation of ethylene (C2H4) from acetylene (C2H2) and carbon dioxide (CO2) using an ultramicroporous metal-organic framework UTSA-16. The synergistic effect of the polarized carboxyl groups and coordinated water molecules in its pore channel enables the material to have high uptakes for C2H2 and CO2 due to electrostatic potential matching, as well as excellent separation selectivity against C2H4. Breakthrough experiments suggest that UTSA-16 can efficiently separate 99.9% pure C2H4 from ternary mixtures with a high productivity of 403 L kg-1. Moreover, the preparation cost of UTSA-16 is significantly lower than other related adsorbents by 40-2000 times, indicating its unique potential for industrial applications.

Efficient recovery of bisphenol A from aqueous solution using K2CO3 activated carbon derived from starch-based polyurethane.

Endocrine-disrupting compounds (EDCs) are increasingly polluting water, making it of practical value to develop novel desirable adsorbents for removing these pollutants from wastewater. Here, a simple cross-linking strategy combined with gentle chemical activation was demonstrated to prepare starch polyurethane-activated carbon (STPU-AC) for adsorbing BPA in water. The adsorbents were characterized by various techniques such as FTIR, XPS, Raman, BET, SEM, and zeta potential, and their adsorption properties were investigated comprehensively. Results show that STPU-AC possesses a large surface area (1862.55 m2·g-1) and an abundance of functional groups, which exhibited superior adsorption capacity for BPA (543.4 mg·g-1) and favorable regenerative abilities. The adsorption of BPA by STPU-AC follows a pseudo-second-order kinetic model and a Freundlich isotherm model. The effect of aqueous solution chemistry (pH and ionic strength) and the presence of other contaminants (phenol, heavy metals, and dyes) on BPA adsorption was also analyzed. Moreover, theoretical studies further demonstrate that hydroxyl oxygen and pyrrole nitrogen are the primary adsorption sites. We found that the efficient recovery of BPA was associated with pore filling, hydrogen-bonding interaction, hydrophobic effects, and π-π stacking. These findings demonstrate the promising practical application of STPU-AC and provide a basis for the rational design of starch-derived porous carbon.

Temperature-dependent rearrangement of gas molecules in ultramicroporous materials for tunable adsorption of CO2 and C2H2.

The interactions between adsorbed gas molecules within porous metal-organic frameworks are crucial to gas selectivity but remain poorly explored. Here, we report the modulation of packing geometries of CO2 and C2H2 clusters within the ultramicroporous CUK-1 material as a function of temperature. In-situ synchrotron X-ray diffraction reveals a unique temperature-dependent reversal of CO2 and C2H2 adsorption affinities on CUK-1, which is validated by gas sorption and dynamic breakthrough experiments, affording high-purity C2H2 (99.95%) from the equimolar mixture of C2H2/CO2 via a one-step purification process. At low temperatures (<253 K), CUK-1 preferentially adsorbs CO2 with both high selectivity (>10) and capacity (170 cm3 g-1) owing to the formation of CO2 tetramers that simultaneously maximize the guest-guest and host-guest interactions. At room temperature, conventionally selective adsorption of C2H2 is observed. The selectivity reversal, structural robustness, and facile regeneration of CUK-1 suggest its potential for producing high-purity C2H2 by temperature-swing sorption.

One-pot fabrication of lignin-based aromatic porous polymers for efficient removal of bisphenol AF from water.

To remove the bisphenol AF (BPAF) from aqueous solution, two different types of lignin-based aromatic porous polymers (LAPP-1 and LAPP-2) were fabricated via one-pot crosslinking of lignin with 1,4-dichloroxylene and 4,4'-bis(chloromethyl)-1,1'-biphenyl, respectively. The successful synthesis of LAPPs was confirmed by FTIR and XPS, SEM, TEM and N2 adsorption-desorption analysis. Then, batch adsorption experiments were conducted to investigate adsorption properties toward BPAF. Based on the results, the adsorption processes were in accordance with the pseudo-second-order kinetic model and the Freundlich isotherm model, and the thermodynamic studies showed that the adsorption was a spontaneous and exothermic process. It is remarkable that LAPPs exhibited good adsorption performance in wide ranges of pH and ionic strength as well as in recycling process. Notably, compared to LAPP-1, LAPP-2 exhibited higher adsorption capacity for BPAF, which can be ascribed to its higher porosity and content of aromatic ring. Moreover, the comprehensive analysis of experimental and theoretical results indicated that the π-π interactions and pore adsorption may jointly drive the uptake process of BPAF. Considering the simple fabrication method employed and excellent BPAF adsorption performance, LAPPs provided new insights into the development of advanced lignin-based adsorbents for removal of BPAF from water.

Cellulose based hyper-crosslinked polymer for efficiently recovering valuable materials from PO/SM wastewater.

Herein, a TEMPO-oxidized cellulose-grafted-polystyrene hypercrosslinked polymer (TOC-PS-HCP) was synthesized facilely by TEMPO oxidation, grafting copolymerization and post crosslinking route. Based on the structural characterization, it was confirmed that TOC-PS-HCP mainly consisted of polystyrene chain on cellulose and rigid crosslinked bridge. Additionally, the as-prepared TOC-PS-HCP displayed appropriate hydrophobicity (water contact angle = 102.44°) and high specific surface area (SBET = 601.20 m2·g--1), which could efficiently recover ethylbenzene and styrene from PO/SM wastewater. The adsorption experiment was conducted to study the recovery performance for ethylbenzene and styrene in the aqueous phase. The results showed that TOC-PS-HCP could recover ethylbenzene and styrene quickly by adsorption process, and maintain a stable recovery rate both in different aqueous conditions and recycle experiments. The adsorption experiment in the simulated wastewater solution showed that TOC-PS-HCP exhibited the greater affinity for ethylbenzene and styrene than other substrates. Furthermore, a possible mechanism for the efficient recovery of ethylbenzene and styrene was suggested on the basis of experimental and theoretical results, which may be associated with van der Waals force and π-π stacking.

ß-Cyclodextrin functionalized SBA-15 via amide linkage as a super adsorbent for rapid removal of methyl blue.

To remove the bulky aqueous organic dye e.g. methyl blue (MB) from water, ordered mesoporous silica SBA-15 has been functionalized with ß-cyclodextrin (ß-CD) via amide linkage. The surface physical and chemical properties of the surface of the resulted ß-CD-functionalized adsorbents (abbrev. SBA15-A-CD) were characterized systematically. The results indicate that the channels of SBA-15 were uniformly modified with amine groups and were further ß-CD-terminated via amide linkages, without ruining its ordered mesoporous structure. The effects of contact time, pH, ionic strength, temperature and salt on the adsorption performance were explored. SBA15-A-CD showed maximum adsorption capacity for MB up to 1791 mg·g-1 combined with excellent recyclability. Besides, the adsorption behavior of MB onto SBA15-A-CD has been investigated by DFT calculation and two-dimensional NMR. Specifically, the enhanced adsorption capacity for MB stems from the tailored host-guest interaction between ß-CD cavity and aromatic moiety of MB in combination with the electrostatic attraction between amine groups and sulfonated group of MB. These findings offer good opportunities for improving the ability of mesoporous silica in adsorption of bulky anion dyes in wastewater.

Immobilized metal affinity chromatography matrix modified by poly (ethylene glycol) methyl ether for purification of angiotensin I-converting enzyme inhibitory peptide from casein hydrolysate.

Purification of small bioactive peptides from complex biological samples is a difficult task due to the interference of concentrated large biomolecules. In this study, a magnetic immobilized metal affinity chromatography matrix modified by poly (ethylene glycol) methyl ether (IMACM@mPEG) was prepared and applied for the rapid purification of angiotensin I-converting enzyme (ACE) inhibitory peptides from casein hydrolysate. The proposed IMACM@mPEG considerably reduced the non-specific adsorption of large proteins and exhibited improved purification efficiency towards ACE inhibitory peptides. A novel peptide with moderate ACE inhibitory activity (IC50 value of 274 ± 5 µM) was identified as LLYQEPVLGPVR. Lineweaver-Burk plot confirmed the non-competitive inhibition pattern of LLYQEPVLGPVR. The purified peptide was digested after simulated gastrointestinal digestion and produced shorter peptides which contributed to enhanced ACE inhibitory activity. These results indicated that the IMACM@mPEG is an effective method for the prepurification of ACE inhibitory peptide and the purified peptide LLYQEPVLGPVR may have potential as nutraceutical ingredient in functional foods for hypertension treatments.

Easy fabrication of aromatic-rich cellulose-urethane polymer for preferential adsorption of acetophenone over 1-phenylethanol.

A novel aromatic-rich cellulose-urethane polymer (ACUP) was easily fabricated by crosslinking cellulose with 4,4',4''-triphenylmethane triisocyanate for preferential adsorption of acetophenone (AP) over 1-phenyethanol (PE). The successful synthesis of ACUP was confirmed by the instrumental analyses, e.g., FTIR, TG, XPS, FE-SEM, 13C CP/MAS NMR and XRD. For single-solute adsorption of AP or PE onto ACUP, the effects of adsorbent dosage, agitation speed, time, solute concentration and temperature were systematically investigated. The overall adsorption process was exothermal and spontaneous in nature, and followed the pseudo-second-order kinetic rate equation and Freundlich isotherm model. Competitive adsorption studies concerning the effects of phenyl content in ACUP adsorbent, pH and ionic strength were also presented, in which ACUP showed much higher affinity for AP over PE. In addition, ACUP was examined as a column packing material for adsorptive separation of the equimolar mixture of AP-PE, showing excellent separation capability. The easily-regenerated and recyclable features of ACUP were demonstrated by adsorption-desorption cycles in both batch and continuous modes. Furthermore, a possible mechanism for the preferential adsorption of AP over PE, which may be associated with π-π and hydrogen bonding interactions was suggested on the basis of experimental and theoretical results.

Rapid and selective recovery of acetophenone from petrochemical effluents by crosslinked starch polymer.

A porous crosslinked starch polymer (CSTO) using bitolylene diisocyanate as crosslinker was prepared by a facile method and used to selectively recover acetophenone (AP) from petrochemical effluent mainly containing AP and 1-phenylethanol (PE). The theoretical calculation results indicated that AP exhibited the superior affinity toward the adsorption sites of CSTO through noncovalent interactions. The adsorption measurements showed that, due to the large surface area and high affinity of phenyl rings, CSTO displayed an extremely rapid adsorption rate, a desirable adsorption capacity and selectivity to AP. The adsorption kinetics and isotherms in single solute system agreed well with the pseudo-second-order kinetic model and Freundlich isotherm model, and the adsorption was exothermic and spontaneous. Furthermore, CSTO showed excellent reusability for selective adsorption of AP from equimolar mixture of AP/PE, prompting us to further examine its applicability. In the practical application, CSTO also revealed a fast, preferential and reusable adsorption of AP from actual petrochemical effluent.

Ultrafast Screening of a Novel, Moderately Hydrophilic Angiotensin-Converting-Enzyme-Inhibitory Peptide, RYL, from Silkworm Pupa Using an Fe-Doped-Silkworm-Excrement-Derived Biocarbon: Waste Conversion by Waste.

A novel, moderately hydrophilic peptide (RYL) with high ACE-inhibitory activity was screened ultrafast via a concept of waste conversion using waste. This novel peptide was screened from silkworm pupa using an Fe-doped porous biocarbon (FL/Z-SE) derived from silkworm excrement. FL/Z-SE possessed magnetic properties and specific selection for peptides due to Fe's dual functions. The selected RYL, which has moderate hydrophilicity (LogP = -0.22), exhibited a comparatively high ACE-inhibitory activity (IC50 = 3.31 ± 0.11 µM). The inhibitory kinetics and docking-simulation results show that, as a competitive ACE inhibitor, RYL formed five hydrogen bonds with the ACE residues in the S1 and S2 pockets. In this work, both the screening carbon material and the selected ACE-inhibitory peptide were derived from agricultural waste (silkworm excrement and pupa), which offers a new way of thinking about the development of advanced uses of the silkworm byproducts and wastes.

High-Throughput and Rapid Screening of Novel ACE Inhibitory Peptides from Sericin Source and Inhibition Mechanism by Using in Silico and in Vitro Prescriptions.

Several novel peptides with high ACE-I inhibitory activity were successfully screened from sericin hydrolysate (SH) by coupling in silico and in vitro approaches for the first time. Most screening processes for ACE-I inhibitory peptides were achieved through high-throughput in silico simulation followed by in vitro verification. QSAR model based predicted results indicated that the ACE-I inhibitory activity of these SH peptides and six chosen peptides exhibited moderate high ACE-I inhibitory activities (log IC50 values: 1.63-2.34). Moreover, two tripeptides among the chosen six peptides were selected for ACE-I inhibition mechanism analysis which based on Lineweaver-Burk plots indicated that they behave as competitive ACE-I inhibitors. The C-terminal residues of short-chain peptides that contain more H-bond acceptor groups could easily form hydrogen bonds with ACE-I and have higher ACE-I inhibitory activity. Overall, sericin protein as a strong ACE-I inhibition source could be deemed a promising agent for antihypertension applications.