Separation of High-Purity C2H2 from Binary C2H2/CO2 Using Robust Al-Based MOFs Comprising Nitrogen-Containing Heterocyclic Dicarboxylate.

In this study, three nitrogen-containing aluminum-based metal-organic frameworks (Al-MOFs), namely, CAU-10pydc, MOF-303, and KMF-1, were investigated for the efficient separation of a C2H2/CO2 gas mixture. Among these three Al-MOFs, KMF-1 demonstrated the highest selectivity for C2H2/CO2 separation (6.31), primarily owing to its superior C2H2 uptake (7.90 mmol g-1) and lower CO2 uptake (2.82 mmol g-1) compared to that of the other two Al-MOFs. Dynamic breakthrough experiments, using an equimolar binary C2H2/CO2 gas mixture, demonstrated that KMF-1 achieved the highest separation performance. It yielded 3.42 mmol g-1 of high-purity C2H2 (>99.95%) through a straightforward desorption process under He purging at 298 K and 1 bar. To gain insights into the distinctive characteristics of the pore surfaces of structurally similar CAU-10pydc and KMF-1, we conducted computational simulations using canonical Monte Carlo and dispersion-corrected density functional theory methods. These simulations revealed that the secondary amine (C2N-H) groups in KMF-1 played a more significant role in differentiating between C2H2 and CO2 compared to that of the N atoms in CAU-10pydc and MOF-303. Consequently, KMF-1 emerged as a promising adsorbent for the separation of high-purity C2H2 from binary C2H2/CO2 gas mixtures.

Design of Pore Properties of an Al-Based Metal-Organic Framework for the Separation of an Ethane/Ethylene Gas Mixture via Ethane-Selective Adsorption.

A series of Al-based isomorphs (CAU-10H, MIL-160, KMF-1, and CAU-10pydc) were synthesized using isophthalic acid (ipa), 2,5-furandicarboxylic acid (fdc), 2,5-pyrrole dicarboxylic acid (pyrdc), and 3,5-pyridinedicarboxylic acid (pydc), respectively. These isomorphs were systematically investigated to identify the best adsorbent for effectively separating C2H6/C2H4. All CAU-10 isomorphs exhibited preferential adsorption of C2H6 over that of C2H4 in mixture. CAU-10pydc exhibited the best C2H6/C2H4 selectivity (1.68) and the highest C2H6 uptake (3.97 mmol g-1) at 298 K and 1 bar. In the breakthrough experiment using CAU-10pydc, 1/1 (v/v) and 1/15 (v/v) C2H6/C2H4 gas mixtures were successfully separated into high-purity C2H4 (>99.95%), with remarkable productivities of 14.0 LSTP kg-1 and 32.0 LSTP kg-1, respectively, at 298 K. Molecular simulations revealed that the exceptional separation performance of CAU-10pydc originated from the increased porosity and reduced electron density of the pyridine ring of pydc, leading to a relatively larger decrease in π-π interactions with C2H4 than in the C-H···π interactions with C2H6. This study demonstrates that the pore size and geometry of the CAU-10 platform are modulated by the inclusion of heteroatom-containing benzene dicarboxylate or heterocyclic rings of dicarboxylate-based organic linkers, thereby fine-tuning the C2H6/C2H4 separation ability. CAU-10pydc was determined to be an optimum adsorbent for this challenging separation.

Tuning Hydrophilicity of Aluminum MOFs by a Mixed-Linker Strategy for Enhanced Performance in Water Adsorption-Driven Heat Allocation Application.

Water adsorption-driven heat transfer (AHT) technology has emerged as a promising solution to address crisis of the global energy consumption and environmental pollution of current heating and cooling processes. Hydrophilicity of water adsorbents plays a decisive role in these applications. This work reports an easy, green, and inexpensive approach to tuning the hydrophilicity of metal-organic frameworks (MOFs) by incorporating mixed linkers, isophthalic acid (IPA), and 3,5-pyridinedicarboxylic acid (PYDC), with various ratios in a series of Al-xIPA-(100-x)PYDC (x: feeding ratio of IPA) MOFs. The designed mixed-linkers MOFs show a variation of hydrophilicity along the fraction of the linkers. Representative compounds with a proportional mixed linker ratio denoted as KMF-2, exhibit an S-shaped isotherm, an excellent coefficient of performance of 0.75 (cooling) and 1.66 (heating) achieved with low driving temperature below 70 °C which offers capability to employ solar or industrial waste heat, remarkable volumetric specific energy capacity (235 kWh m-3 ) and heat-storage capacity (330 kWh m-3 ). The superiority of KMF-2 to IPA or PYDC-containing single-linker MOFs (CAU-10-H and CAU-10pydc, respectively) and most of benchmark adsorbents illustrate the effectiveness of the mixed-linker strategy to design AHT adsorbents with promising performance.

An Amine-Functionalized Ultramicroporous Metal-Organic Framework for Postcombustion CO2 Capture.

Among the most promising methods by which to capture CO2 from flue gas, the emission of which has accelerated global warming, is energy-efficient physisorption using metal-organic framework (MOF) adsorbents. Here, we present a novel cuprous-based ultramicroporous MOF, Cu(adci)-2 (adci- = 2-amino-4,5-dicyanoimidazolate), which was rationally synthesized by combining two strategies to design MOF physisorbents for enhanced CO2 capturing, i.e., aromatic amine functionalization and the introduction of ultramicroporosity (pore size <7 Å). Synchrotron powder X-ray diffraction and a Rietveld analysis reveal that the Cu(adci)-2 structure has one-dimensional square-shaped channels, in each of which all affiliated ligands, specifically NH2 groups at the 2-position of the imidazolate ring, have the same orientation, with a pair of NH2 groups therefore facing each other on opposite sides of the channel walls. While Cu(adci)-2 exhibits a high CO2 adsorption capacity (2.01 mmol g-1 at 298 K and 15 kPa) but a low zero-coverage isosteric heat of adsorption (27.5 kJ mol-1), breakthrough experiments under dry and 60% relative humidity conditions show that its CO2 capture ability is retained even in the presence of high amounts of moisture. In a Monte Carlo simulation and a radial distribution analysis, the preferential CO2 binding site of Cu(adci)-2 was predicted to be between two ligands, forming a sandwich-like structure and implying that its CO2 adsorption properties originate from the enhancement of Lewis base-acid and London dispersion interactions due to the amino groups and ultramicroporosity, respectively.

High-Performance Adsorbent for Ethane/Ethylene Separation Selected through the Computational Screening of Aluminum-Based Metal-Organic Frameworks.

The development of a high-performance ethane (C2H6)-selective adsorbent for the separation of ethane/ethylene (C2H6/C2H4) gas mixtures has been investigated for high-efficiency adsorption-based gas separation. Herein, we investigated Al-based metal-organic frameworks (MOFs) to identify an efficient C2H6-selective adsorbent (CAU-11), supported by a computational simulation study. CAU-11 exhibited numerous advantageous properties (such as low material cost, structural robustness, high reaction yield, and high C2H6/C2H4 selectivity) compared to other Al-based MOFs, indicating immense potential as a C2H6-selective adsorbent. CAU-11 exhibited preferential C2H6 adsorption in single-component gas adsorption experiments, and its predicted ideal adsorption solution theory selectivity of C2H6/C2H4 was over 2.1, consistent with the simulation analysis. Dynamic breakthrough experiments using representative compositions of the C2H6/C2H4 gas mixture confirmed the excellent separation ability of CAU-11; it produced high-purity C2H4 (>99.95%) with productivity values of 0.79 and 2.02 mol L-1 while repeating the cyclic experiment with 1:1 and 1:15 v/v C2H6/C2H4 gas mixtures, respectively, at 298 K and 1 bar. The high C2H6/C2H4 separation ability of CAU-11 could be attributed to its non-polar pore environment and optimum pore dimensions which strengthen the interaction of its pores (via C-H···π interactions) with C2H6 to a greater extent than with C2H4.

Separation of Branched Alkanes Feeds by a Synergistic Action of Zeolite and Metal-Organic Framework.

Zeolites and metal-organic frameworks (MOFs) are considered as "competitors" for new separation processes. The production of high-quality gasoline is currently achieved through the total isomerization process that separates pentane and hexane isomers while not reaching the ultimate goal of a research octane number (RON) higher than 92. This work demonstrates how a synergistic action of the zeolite 5A and the MIL-160(Al) MOF leads to a novel adsorptive process for octane upgrading of gasoline through an efficient separation of isomers. This innovative mixed-bed adsorbent strategy encompasses a thermodynamically driven separation of hexane isomers according to the degree of branching by MIL-160(Al) coupled to a steric rejection of linear isomers by the molecular sieve zeolite 5A. Their adsorptive separation ability is further evaluated under real conditions by sorption breakthrough and continuous cyclic experiments with a mixed bed of shaped adsorbents. Remarkably, at the industrially relevant temperature of 423 K, an ideal sorption hierarchy of low RON over high RON alkanes is achieved, i.e., n-hexane ≫ n-pentane ≫ 2-methylpentane > 3-methylpentane ⋙ 2,3-dimethylbutane > isopentane ≈ 2,2-dimethylbutane, together with a productivity of 1.14 mol dm-3 and a high RON of 92, which is a leap-forward compared with existing processes.

Crystals springing into action: metal-organic framework CUK-1 as a pressure-driven molecular spring.

Mercury porosimetry and in situ high pressure single crystal X-ray diffraction revealed the wine-rack CUK-1 MOF as a unique crystalline material capable of a fully reversible mechanical pressure-triggered structural contraction. The near-absence of hysteresis upon cycling exhibited by this robust MOF, akin to an ideal molecular spring, is associated with a constant work energy storage capacity of 40 J g-1. Molecular simulations were further deployed to uncover the free-energy landscape behind this unprecedented pressure-responsive phenomenon in the area of compliant hybrid porous materials. This discovery is of utmost importance from the perspective of instant energy storage and delivery.

Catalytic Performance of Zr-Based Metal-Organic Frameworks Zr-abtc and MIP-200 in Selective Oxidations with H2 O2.

The catalytic performance of Zr-abtc and MIP-200 metal-organic frameworks consisting of 8-connected Zr6 clusters and tetratopic linkers was investigated in H2 O2 -based selective oxidations and compared with that of 12-coordinated UiO-66 and UiO-67. Zr-abtc demonstrated advantages in both substrate conversion and product selectivity for epoxidation of electron-deficient C=C bonds in α,ß-unsaturated ketones. The significant predominance of 1,2-epoxide in carvone epoxidation, coupled with high sulfone selectivity in thioether oxidation, points to a nucleophilic oxidation mechanism over Zr-abtc. The superior catalytic performance in the epoxidation of unsaturated ketones correlates with a larger amount of weak basic sites in Zr-abtc. Electrophilic activation of H2 O2 can also be realized, as evidenced by the high activity of Zr-abtc in epoxidation of the electron-rich C=C bond in caryophyllene. XRD and FTIR studies confirmed the retention of the Zr-abtc structure after the catalysis. The low activity of MIP-200 in H2 O2 -based oxidations is most likely related to its specific hydrophilicity, which disfavors adsorption of organic substrates and H2 O2 .

Water adsorption fingerprinting of structural defects/capping functions in Zr-fumarate MOFs: a hybrid computational-experimental approach.

Engineering structural defects in MOFs has been intensively applied to modulate their adsorption-related properties. Zr-fumarate MOF (also known as MOF-801) is a prototypical defective MOF with proven versatile adsorption/separation performances depending on the synthetic conditions, however the relationship between the nature/concentration of both structure defects/capping functions and its adsorption features is still far from being fully understood. In this work, we first present a systematic theoretical exploration of the individual contributions of linker and cluster defects as well as of the capping functions to the overall water adsorption profile of the MOF-801 framework. This computational effort based on the construction of defective structure models and the use of Grand Canonical Monte Carlo simulations further enabled the identification of the overarching defective structure for two MOF-801 samples based on their experimental adsorption isotherms reported previously. An experimental effort was then deployed to synthesize two Zr-fumarate MOF samples with controlled nature and concentration of structural defects as well as capping functions. This computational-experimental hybrid strategy revealed the water adsorption isotherm as a fingerprint of the nature and concentration of structural defect/capping groups exhibited by the MOF adsorbent. We expect this study to deliver meaningful insights to further design MOFs with target adsorption features through a rational engineering of structural defects.

Defective Zr-Fumarate MOFs Enable High-Efficiency Adsorption Heat Allocations.

Adsorption-driven heat transfer devices incorporating an efficient "adsorbent-water" working pair are attracting great attention as a green and sustainable technology to address the huge global energy demands for cooling and heating. Herein, we report the improved heat transfer performance of a defective Zr fumarate metal-organic framework (MOF) prepared in a water solvent (Zr-Fum HT). This material exhibits an S-shaped water sorption isotherm (P/P0 = 0.05-0.2), excellent working capacity (0.497 mLH2O mL-1MOF) under adsorption-driven cooling/chiller working conditions (Tadsorption(ads) = 30 °C, Tcondensation (con) = 30 °C, and Tdesorption(des) = 80 °C), very high coefficient of performances for both cooling (0.83) and heating (1.76) together with a relatively low driving temperature at 80 °C, a remarkable heat storage capacity (423.6 kW h m-3MOF), and an outstanding evaporation heat (343.8 kW h m-3MOF). The level of performance of the resultant Zr-Fum HT MOF is above those of all existing benchmark water adsorbents including MOF-801 previously synthesized in the N,N-dimethylformamide solvent under regeneration at 80 °C which is accessible from the solar source. This is coupled with many other decisive advantages including green synthesis and high proven chemical and mechanical robustness. The microscopic water adsorption mechanism of Zr-Fum HT at the origin of its excellent water adsorption performance was further explored computationally based on the construction of an atomistic defective model online with the experimental data gained from a subtle combination of characterization techniques.

Rational design of a robust aluminum metal-organic framework for multi-purpose water-sorption-driven heat allocations.

Adsorption-driven heat transfer technology using water as working fluid is a promising eco-friendly strategy to address the exponential increase of global energy demands for cooling and heating purposes. Here we present the water sorption properties of a porous aluminum carboxylate metal-organic framework, [Al(OH)(C6H3NO4)]·nH2O, KMF-1, discovered by a joint computational predictive and experimental approaches, which exhibits step-like sorption isotherms, record volumetric working capacity (0.36 mL mL-1) and specific energy capacity (263 kWh m-3) under cooling working conditions, very high coefficient of performances of 0.75 (cooling) and 1.74 (heating) together with low driving temperature below 70 °C which allows the exploitation of solar heat, high cycling stability and remarkable heat storage capacity (348 kWh m-3). This level of performances makes this porous material as a unique and ideal multi-purpose water adsorbent to tackle the challenges of thermal energy storage and its further efficient exploitation for both cooling and heating applications.

Unique design of superior metal-organic framework for removal of toxic chemicals in humid environment via direct functionalization of the metal nodes.

Unique chemical and thermal stabilities of a zirconium-based metal-organic framework (MOF) and its functionalized analogues play a key role to efficiently remove chemical warfare agents (ex., cyanogen chloride, CNCl) and simulant (dimethyl methylphosphonate, DMMP) as well as industrial toxic gas, ammonia (NH3). Herein, we for the first time demonstrate outstanding performance of MOF-808 for removal of toxic chemicals in humid environment via special design of functionalization of hydroxo species bridging Zr-nodes using a triethylenediamine (TEDA) to form ionic frameworks by gas phase acid-base reactions. In situ experimental analyses and first-principles density functional theory calculations unveil underlying mechanism on the selective deposition of TEDA on the Zr-bridging hydroxo sites (µ3-OH) in Zr-MOFs. The crystal structure of TEDA-grafted MOF-808 was confirmed using synchrotron X-ray powder diffraction (SXRPD). Furthermore, operando FT-IR spectra elucidate why the TEDA-grafted MOF-808 shows by far superior sorption efficiency to other MOF varieties. This work provides design principles and applications how to optimize MOFs for the preparation for versatile adsorbents using diamine grafting chemistry, which is also potentially applicable to various catalysis.

Porous Metal-Organic Framework CUK-1 for Adsorption Heat Allocation toward Green Applications of Natural Refrigerant Water.

The development of new water adsorbents that are hydrothermally stable and can operate more efficiently than existing materials is essential for the advancement of water adsorption-driven chillers. Most of the existing benchmark materials and related systems in this field suffer from clear limitations that must be overcome to meet global requirements for sustainable and green energy production and utilization. Here, we report the energy-efficient water sorption properties of three isostructural metal-organic frameworks (MOFs) based on the simple ligand pyridine-2,4-dicarboxylate, named M-CUK-1 [M3(µ3-OH)2(2,4-pdc)2] (where M = Co2+, Ni2+, or Mg2+). The highly hydrothermally stable CUK-1 series feature step-like water adsorption isotherms, relatively high H2O sorption capacities between P/P0 = 0.10-0.25, stable cycling, facile regeneration, and, most importantly, benchmark coefficient of performance values for cooling and heating at a low driving temperature. Furthermore, these MOFs are prepared under green hydrothermal conditions in aqueous solutions. Our joint experimental-computational approach revealed that M-CUK-1 integrates several optimal features, resulting in promising materials as advanced water adsorbents for adsorption-driven cooling and heating applications.

Molecular Encapsulation of Trimeric Chromium Carboxylate Clusters in Metal-Organic Frameworks and Propylene Sorption.

Oxo-bridged trimeric chromium acetate clusters [Cr3 O(OOCCH3 )6 (H2 O)3 ]NO3 have been encapsulated for the first time in the mesoporous cages of the chromium terephthalate MIL-101(Cr). The isolated clusters in MIL-101(Cr) have increased affinity towards propylene compared to propane, due to generation of a new kind of pocket-based propylene-binding site, as supported by DFT calculations.

Flexible Energy Harvester Based on Poly(vinylidene fluoride) Composite Films.

In these days, we are facing emerging energy crisis due to depletion of fossil fuels. Therefore, renewable energy which is based on wind energy, mechanical force energy, microwave energy and vibrations energy have attracted a lot of attentions. Piezoelectric energy harvesting is one of the promising renewable energy sources. As the use portable electronic devices increases, the need for portable renewable energy sources further increases. Especially, piezoelectric materials can be the best selection due to their robust properties. In this research, piezoelectric composites were prepared and investigated for piezoelectric energy harvesting applications. In this study, two types of flexible energy harvesters, 0.36BS-0.64PT-PVDF composite and PVDF film, were prepared and analyzed. Due to its high Curie temperature and low lead content, BS-PT is expected to be a substitute for PZT in the near future. The composite materials based on the PVDF and 0.36BS-0.64PT film showed higher open circuit voltage (0.73 V) than PVDF film (0.49 V). Also, the stored voltage of 0.36BS-0.64PT-PVDF composite film was 330 nJ which is 5.68 times higher than 58 nJ for PVDF films. By introducing the piezoelectric BS-PT ceramics, 0.36BS-0.64PT-PVDF composite film shows the enhanced performance such as open circuit voltage, energy and dielectric constant compared with those of PVDF materials. It seems that 0.36BS-0.64PT-PVDF composite film is more suitable for flexible energy device.

Spring-Based Active Shock Absorber Systems with Piezoelectric Energy Harvesters.

In this research, energy harvesters with different types of spring-based shock absorbers were invested for the active shock absorber applications. Two different types of spring-based shock absorbers were prepared for the comparison, coil type spring-based shock absorbers and specially designed slice type spring-based shock absorbers. Shock absorbers have been widely employed to protect the complicated main system by cancelling the applied mechanical forces from outsides. Therefore, in the classical points of view, shock absorber can be prepared by the elastic materials to store and release the applied mechanical energy with sequentially in the form of elastic energy, thermal energy, and sound energy. However, in recently, there are strong demands to replace this classical shock absorber to the energy harvesters, which can collect the wasted energy in the form of electrical energy. Therefore, in this research, alternative two different types of spring-based advanced shock absorber will be presented and discussed. To combine with the spring-based shock absorber, multilayered piezoelectric energy harvesters were attached to collect the applied mechanical energy.

Enhanced Ferroelectric and Piezoelectric Properties of (1-x)PMN-xPT Ceramics Based on a Partial Oxalate Process.

The pyrochlore phase in ferroelectric and piezoelectric materials is the main obstacle device application due to its poor electrical properties. Especially, the pyrochlore phase is frequently observed in the perovskite-based metal-oxide materials including piezoelectric and ferroelectric ceramics, which are based on solid-state reaction methods for fabrication. To overcome these problems, advanced innovative methods such as partial oxalate process will be investigated. In this method, crystalized magnesium niobite (MN) and lead titanate (PT) powders will be coated with a certain amount of lead oxalate and, then, the calcination process can be carried out to form the PMN-PT without pyrochlore phase. In this study, (1-x)PMN-xPT ceramics near the morphotropic phase boundary (MPB), with compositions of x = 0.25⁻0.40, have been prepared employing the partial oxalate method at various temperatures. The crystalline, microstructure, and piezoelectric properties of (1-x)PMN-xPT ceramics depending on the sintering temperature were intensively investigated and discussed. By optimizing the sintering temperature and compositions from the PMN-PT ceramics, the maximum value of the piezoelectric charge coefficient (d33) of 665pC/N, planar electromechanical coupling factor (kp) of 77.8%, dielectric constant (εr) of 3230, and remanent polarization (Pr) of 31.67 µC/cm² were obtained.

Piezoelectric Energy Generators Based on Spring and Inertial Mass.

In this study, inertial mass-based piezoelectric energy generators with and without a spring were designed and tested. This energy harvesting system is based on the shock absorber, which is widely used to protect humans or products from mechanical shock. Mechanical shock energies, which were applied to the energy absorber, were converted into electrical energies. To design the energy harvester, an inertial mass was introduced to focus the energy generating position. In addition, a spring was designed and tested to increase the energy generation time by absorbing the mechanical shock energy and releasing a decreased shock energy over a longer time. Both inertial mass and the spring are the key design parameters for energy harvesters as the piezoelectric materials, Pb(Mg1/3Nb2/3)O3-PbTiO3 piezoelectric ceramics were employed to store and convert the mechanical force into electric energy. In this research, we will discuss the design and performance of the energy generator system based on shock absorbers.

Can pelagic ciliates indicate vertical variation in the water quality status of western Arctic pelagic ecosystems?

The vertical pattern of pelagic ciliate communities was observed at eight layers in the Chukchi Sea and the northern Bering Sea of the western Arctic Ocean during the summer sea-ice reduction period (August 5 to August 24, 2016). A total of 44 ciliate species were identified, with seven species dominated the communities in the water column. Multivariate and univariate analyses demonstrated that: (1) community structures of ciliates vary significantly among eight water depths; (2) variations in the vertical distribution of ciliates were significantly correlated with changes in physicochemical variables, especially the ammonia; (3) the distributions of the three dominant species were significantly and positively related to the chlorophyll a and ammonia concentrations; and (4) species richness and abundance were significantly and positively correlated with the concentrations of ammonia and chlorophyll a. These results suggest that pelagic ciliates may reflect vertical variations in the water quality status of western Arctic ecosystems.

Novel amine-functionalized iron trimesates with enhanced peroxidase-like activity and their applications for the fluorescent assay of choline and acetylcholine.

We herein describe novel amine-grafted metal-organic frameworks (MOFs) as a promising alternative to natural peroxidase enzyme and their applications for a fluorescent assay of choline (Cho) and acetylcholine (ACh). Among diverse amine-functionalized MOFs, N,N,N',N'-tetramethyl-1,4-butanediamine (TMBDA)-functionalized MIL-100(Fe) (TMBDA-MIL-100(Fe)) exhibited the highest peroxidase activity by developing intense fluorescence from Amplex UltraRed (AUR) in the presence of H2O2, which was presumably due to the synergetic effect of the enhanced negative potential and precisely controlled molecular size of the grafted diamine. Based on the excellent peroxidase-like activity of TMBDA-MIL-100(Fe), choline and ACh were reliably determined down to 0.027 and 0.036µM, respectively. Furthermore, practical applicability of this strategy was successfully demonstrated by detecting choline and ACh in spiked samples of milk and serum, respectively. This work highlights the advantages of amine-grafted MOFs for the preparation of biomimetic catalysts, extending their scope to biosensor applications.