A Polyzwitterionic@MOF Hydrogel with Exceptionally High Water Vapor Uptake for Efficient Atmospheric Water Harvesting.

Atmospheric water harvesting (AWH) is considered a promising strategy for sustainable freshwater production in landlocked and arid regions. Hygroscopic salt-based composite sorbents have attracted widespread attention for their water harvesting performance, but suffer from aggregation and leakage issues due to the salting-out effect. In this study, we synthesized a PML hydrogel composite by incorporating zwitterionic hydrogel (PDMAPS) and MIL-101(Cr) as a host for LiCl. The PML hydrogel was characterized using various techniques including X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FTIR), and thermogravimetric analysis (TGA). The swelling properties and water vapor adsorption-desorption properties of the PML hydrogel were also assessed. The results demonstrate that the MIL-101(Cr) was uniformly embedded into PDMAP hydrogel, and the PML hydrogel exhibits a swelling ratio of 2.29 due to the salting-in behavior. The PML hydrogel exhibited exceptional water vapor sorption capacity of 0.614 g/g at 298 K, RH = 40% and 1.827 g/g at 298 K, RH = 90%. It reached 80% of its saturated adsorption capacity within 117 and 149 min at 298 K, RH = 30% and 90%, respectively. Additionally, the PML hydrogel showed excellent reversibility in terms of water vapor adsorption after ten consecutive cycles of adsorption-desorption. The remarkable adsorption capacity, favorable adsorption-desorption rate, and regeneration stability make the PML hydrogel a potential candidate for AWH. This polymer-MOF synergistic strategy for immobilization of LiCl in this work offers new insights into designing advanced materials for AWH.

Efficient Selective Capture of Carbon Dioxide from Nitrogen and Methane Using a Metal-Organic Framework-Based Nanotrap.

Selective carbon capture from exhaust gas and biogas, which mainly involves the separation of CO2/N2 and CO2/CH4 mixtures, is of paramount importance for environmental and industrial requirements. Herein, we propose an interesting metal-organic framework-based nanotrap, namely ZnAtzCO3 (Atz- = 3-amino-1,2,4-triazolate, CO32- = carbonate), with a favorable ultramicroporous structure and electrostatic interactions that facilitate efficient capture of CO2. The structural composition and stability were verified by FTIR, TGA, and PXRD techniques. Particularly, ZnAtzCO3 demonstrated high CO2 capacity in a wide range of pressures, with values of 44.8 cm3/g at the typical CO2 fraction of the flue gas (15 kPa) and 56.0 cm3/g at the CO2 fraction of the biogas (50 kPa). Moreover, ultrahigh selectivities over CO2/N2 (15:85, v:v) and CO2/CH4 (50:50, v:v) of 3538 and 151 were achieved, respectively. Molecular simulations suggest that the carbon atom of CO2 can form strong electrostatic Cδ+···Î´-O-C interactions with four oxygen atoms in the carbonate ligands, while the oxygen atom of CO2 can interact with the hydrogen atoms in the triazolate ligands through Oδ-···Î´+H-C interactions, which makes ZnAtzCO3 an optimal nanotrap for CO2 fixation. Furthermore, breakthrough experiments confirmed excellent real-world separation toward CO2/N2 and CO2/CH4 mixtures on ZnAtzCO3, demonstrating its great potential for selective CO2 capture.

A Microporous Zn(bdc)(ted)0.5 with Super High Ethane Uptake for Efficient Selective Adsorption and Separation of Light Hydrocarbons.

Separating light hydrocarbons (C2H6, C3H8, and C4H10) from CH4 is challenging but important for natural gas upgrading. A microporous metal-organic framework, Zn(bdc)(ted)0.5, based on terephthalic acid (bdc) and 1,4-diazabicyclo[2.2.2]octane (ted) ligands, is synthesized and characterized through various techniques, including powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and porosity analysis. The adsorption isotherms of light hydrocarbons on the material are measured and the isosteric adsorption heats of CH4, C2H6, C3H8, and C4H10 are calculated. The prediction of C2-4/C1 adsorption selectivities is accomplished using ideal adsorbed solution theory (IAST). The results indicate that the material exhibits exceptional characteristics, including a Brunauer-Emmett-Teller (BET) surface area of 1904 m2/g and a pore volume of 0.73 cm3/g. Notably, the material demonstrates remarkable C2H6 adsorption capacities (4.9 mmol/g), while CH4 uptake remains minimal at 0.4 mmol/g at 298 K and 100 kPa. These findings surpass those of most reported MOFs, highlighting the material's outstanding performance. The isosteric adsorption heats of C2H6, C3H8, and C4H10 on the Zn(bdc)(ted)0.5 are higher than CH4, suggesting a stronger interaction between C2H6, C3H8, and C4H10 molecules and Zn(bdc)(ted)0.5. The molecular simulation reveals that Zn(bdc)(ted)0.5 prefers to adsorb hydrocarbon molecules with richer C-H bonds and larger polarizability, which results in a stronger dispersion force generated by an adsorbent-adsorbate induced polarization effect. Therefore, the selectivity of C4H10/CH4 is up to 180 at 100 kPa, C3H8/CH4 selectivity is 67, and the selectivity of C2H6/CH4 is 13, showing a great potential for separating C2-4 over methane.

Two Facile Aniline-Based Hypercrosslinked Polymer Adsorbents for Highly Efficient Iodine Capture and Removal.

Effective capture and safe disposal of radioactive iodine (129I or 131I) during nuclear power generation processes have always been a worldwide environmental concern. Low-cost and high-efficiency iodine removal materials are urgently needed. In this study, we synthesized two aniline-based hypercrosslinked polymers (AHCPs), AHCP-1 and AHCP-2, for iodine capture in both aqueous and gaseous phases. They are obtained by aniline polymerization through Friedel-Crafts alkylation and Scholl coupling reaction, respectively, with high chemical and thermal stability. Notably, AHCP-1 exhibits record-high static iodine adsorption (250 wt%) in aqueous solution. In the iodine vapor adsorption, AHCP-2 presents an excellent total iodine capture (596 wt%), surpassing the most reported amorphous polymer adsorbents. The rich primary amine groups of AHCPs promote the rapid physical capture of iodine from iodine water and iodine vapor. Intrinsic features such as low-cost preparation, good recyclability, as well as excellent performance in iodine capture indicate that the AHCPs can be used as potential candidates for the removal of iodine from radioactive wastewater and gas mixtures.

Multivariate Metal-Organic Frameworks Prepared by Simultaneous Metal/Ligand Exchange for Enhanced C2-C3 Selective Recovery from Natural Gas.

Recovering light alkanes from natural gas is a critical but challenging process in petrochemical production. Herein, we propose a postmodification strategy via simultaneous metal/ligand exchange to prepare multivariate metal-organic frameworks with enhanced capacity and selectivity of ethane (C2H6) and propane (C3H8) for their recovery from natural gas with methane (CH4) as the primary component. By utilizing the Kuratowski-type secondary building unit of CFA-1 as a scaffold, namely, {Zn5(OAc)4}6+, the Zn2+ metal ions and OAc- ligands were simultaneously exchanged by other transition metal ions and halogen ligands under mild conditions. Inspiringly, this postmodification treatment can give rise to improved capacity for C2H6 and C3H8 without a noticeable increase in CH4 uptake, and consequently, it resulted in significantly enhanced selectivity toward C2H6/CH4 and C3H8/CH4. In particular, by adjusting the species and amount of the modulator, the optimal sample CFA-1-NiCl2-2.3 demonstrated the maximum capacities of C2H6 (5.00 mmol/g) and C3H8 (8.59 mmol/g), increased by 29 and 32% compared to that of CFA-1. Moreover, this compound exhibited excellent separation performance toward C2H6/CH4 and C3H8/CH4, with high uptake ratios of 6.9 and 11.9 at 298 K and 1 bar, respectively, superior to the performance of a majority of the reported MOFs. Molecular simulations were applied to unravel the improved separation mechanism of CFA-1-NiCl2-2.3 toward C2H6/CH4 and C3H8/CH4. Furthermore, remarkable thermal/chemical robustness, moderate isosteric heat, and fully reproducible breakthrough experiments were confirmed on CFA-1-NiCl2-2.3, indicating its great potential for light alkane recovery from natural gas.

An overview of the direct and indirect effects of acid rain on plants: Relationships among acid rain, soil, microorganisms, and plants.

Acid rain (AR) causes numerous environmental problems and complex negative effects on plants globally. Many studies have previously reported on direct effects of AR or its depositional substances on plant injury and performance. However, few studies have addressed the indirect effects of AR on plants as mediated by soil microorganisms and the abiotic environment of the soil rhizosphere. The indirect effects (e.g., AR â†’ soil microorganisms→plants) need greater attention, because acidic deposition not only affects the distribution, composition, abundance, function, and activity of plant-associated microorganisms, but also influences the dynamics of some substances in the soil in a way that may be harmful to plants. Therefore, this review not only focused on the direct effects of AR on plant performance, growth, and biomass allocations from a whole-plant perspective, but also addressed the pathway of AR-soil chemical characteristics-plants, which explains how soil solute leaching and acidification by AR will reduce the availability of essential nutrients and increase the availability of heavy metals for plants, affecting carbon and nitrogen cycles. Mainly, we evaluated the AR-soil microorganisms-plants pathway by: 1) synthesizing the potential roles of soil microbes in alleviating soil acidic stress on plants and the adverse effects of AR on plant-associated soil microorganisms; 2) exploring how plant mycorrhizal types affect the detection of AR effect on plants. The meta-analysis showed that the effects of AR-induced pH on leaf chlorophyll content, plant height, and plant root biomass were dependent on plant mycorrhizal types. Some possible reasons for different synergy between mycorrhizal symbiotic types and plants were discussed. Future research relating to the effects of AR on plants should focus on the combined direct and indirect effects to evaluate how AR affects plant performance comprehensively.

Selective Adsorption of Ethane over Ethylene in PCN-245: Impacts of Interpenetrated Adsorbent.

The separation of ethane from ethylene using cryogenic distillation is an energy-intensive process in the industry. With lower energetic consumption, the adsorption technology provides the opportunities for developing the industry with economic sustainability. We report an iron-based metal-organic framework PCN-245 with interpenetrated structures as an ethane-selective adsorbent for ethylene/ethane separation. The material maintains stability up to 625 K, even after exposure to 80% humid atmosphere for 20 days. Adsorptive separation experiments on PCN-245 at 100 kPa and 298 K indicated that ethane and ethylene uptakes of PCN-245 were 3.27 and 2.39 mmol, respectively, and the selectivity of ethane over ethylene was up to 1.9. Metropolis Monte Carlo calculations suggested that the interpenetrated structure of PCN-245 created greater interaction affinity for ethane than ethylene through the crossing organic linkers, which is consistent with the experimental results. This work highlights the potential application of adsorbents with the interpenetrated structure for ethane separation from ethylene.

Iron-Based Metal-Organic Framework with Hydrophobic Quadrilateral Channels for Highly Selective Separation of Hexane Isomers.

A novel iron-based microporous metal-organic framework built of trinuclear iron clusters [Fe3(µ3-O)(COO)6] and 2,2-bis(4-carboxyphenyl)-hexafluoropropane (6FDCA) has been prepared by solvothermal synthesis. It exhibits excellent chemical stability and strong hydrophobic character. More importantly, this material is capable of separating hexane isomers with good separation performance on the basis of a kinetically controlled process, making it a promising candidate for improving the research octane number of gasoline.