Quasi-open Cu(I) sites for efficient CO separation with high O2/H2O tolerance.

Carbon monoxide (CO) separation relies on chemical adsorption but suffers from the difficulty of desorption and instability of open metal sites against O2, H2O and so on. Here we demonstrate quasi-open metal sites with hidden or shielded coordination sites as a promising solution. Possessing the trigonal coordination geometry (sp2), Cu(I) ions in porous frameworks show weak physical adsorption for non-target guests. Rational regulation of framework flexibility enables geometry transformation to tetrahedral geometry (sp3), generating a fourth coordination site for the chemical adsorption of CO. Quantitative breakthrough experiments at ambient conditions show CO uptakes up to 4.1 mmol g-1 and CO selectivity up to 347 against CO2, CH4, O2, N2 and H2. The adsorbents can be completely regenerated at 333-373 K to recover CO with a purity of >99.99%, and the separation performances are stable in high-concentration O2 and H2O. Although CO leakage concentration generally follows the structural transition pressure, large amounts (>3 mmol g-1) of ultrahigh-purity (99.9999999%, 9N; CO concentration < 1 part per billion) gases can be produced in a single adsorption process, demonstrating the usefulness of this approach for separation applications.

Isomeric Porous Cu(I) Triazolate Frameworks Showing Periodic and Aperiodic Flexibility for Efficient CO Separation.

Guest-induced (crystal-to-crystal) transformation, i.e., periodic flexibility, is a typical feature of molecule-based crystalline porous materials, but its role for adsorptive separation is controversial. On the other hand, aperiodic flexibility is rarely studied. This work reports a pair of isomeric Cu(I) triazolate frameworks, namely, α-[Cu(fetz)] (MAF-2Fa) and ß-[Cu(fetz)] (MAF-2Fb), which show typical periodic and aperiodic flexibility for CO chemical adsorption, respectively. Quantitative mixture breakthrough experiments show that, while MAF-2Fa exhibits high adsorption capacity at high pressures but negligible adsorption below the threshold pressure and with leakage concentrations of 3-8%, MAF-2Fb exhibits relatively low adsorption capacity at high pressures but no leakage (residual CO concentration <1 ppb). Tandem connection of MAF-2Fa and MAF-2Fb can combine their advantages of high CO adsorption capacities at high and low pressures, respectively. MAF-2Fa and MAF-2Fb can both keep the separation performances unchanged at high relative humidities, but only MAF-2Fb shows a unique coadsorption behavior at a relative humidity of 82%, which can be used to improve purification performances.

Molecular-Sieving Separation of Methanol/Benzene Azeotrope by a Flexible Metal-Organic Framework.

Separation of methanol/benzene azeotrope mixtures is very challenging not only by the conventional distillation technique but also by adsorbents. In this work, we design and synthesize a flexible Ca-based metal-organic framework MAF-58 consisting of cheap raw materials. MAF-58 shows selective methanol-induced pore-opening flexibility. Although the opened pores are large enough to accommodate benzene molecules, MAF-58 shows methanol/benzene molecular sieving with ultrahigh experimental selectivity, giving 5.1 mmol g-1 high-purity (99.99%+) methanol and 2.0 mmol g-1 high-purity (99.97%+) benzene in a single adsorption/desorption cycle. Computational simulations reveal that the preferentially adsorbed, coordinated methanol molecules act as the gating component to selectively block the diffusion of benzene, offering a new gating adsorption mechanism.

High-Pressure Molecular Sieving of High-Humidity C2H4/C2H6 Mixture by a Hydrophobic Flexible Metal-Organic Framework.

Molecular sieving is an ideal separation mechanism, but controlling pore size, restricting framework flexibility, and avoiding strong adsorption are all very challenging. Here, we report a flexible adsorbent showing molecular sieving at ambient temperature and high pressure, even under high humidity. While typical guest-induced transformations are observed, a high transition pressure of 16.6 atm is observed for C2H4 at 298 K because of very weak C2H4 adsorption (~16 kJ mol-1). Also, C2H6 is completely excluded below the pore-opening pressure of 7.7 atm, giving single-component selectivity of ca. 300. Quantitative high-pressure column breakthrough experiments using 1 : 1 C2H4/C2H6 mixtures at 10 atm as input confirm molecular sieving with C2H4 adsorption of 0.73 mmol g-1 or 32 cm3(STP) cm-3 and negligible C2H6 adsorption of 0.001(2) mmol g-1, and the adsorbent can be completely regenerated by inert gas purging. Furthermore, it is highly hydrophobic with negligible water adsorption, and the C2H4/C2H6 separation performance is unaffected at high humidity.

On the Role of Flexibility for Adsorptive Separation.

Chemical separations, mostly based on heat-driven techniques such as distillation, account for a large portion of the world's energy consumption. In principle, differential adsorption is a more energy-efficient separation method, but conventional adsorbent materials are still not effective for many industry-relevant mixtures. Porous coordination polymers (PCPs), or metal-organic frameworks (MOFs), are attractive for their well-defined, designable, modifiable, and flexible structures connecting to various potential applications. While the importance of the structural flexibility of MOFs in adsorption-based functions has been demonstrated, the understanding of this special feature is still in its infancy and mostly stays at the periodic structural transformation at the equilibrium state and the special shapes of single-component adsorption isotherms. There are many confusions about the categorization and roles of various types of flexibility. This Account discusses the role of flexibility of MOFs for adsorptive separation, mainly from the thermodynamic and kinetic points of view.As the classic type of framework flexibility, guest-driven structural transformations and the corresponding adsorption isotherms can be thermodynamically described by the energies of the host-guest system. The highly guest-specific pore-opening action showing contrasting single-component adsorption isotherms is regarded as a strategy for achieving molecular sieving without the need for aperture size control, but its effect and role for mixture separation are still controversial. Quantitative mixture adsorption/separation experiments showed that the common periodic (cooperative) pore-opening action leads to coadsorption of molecules smaller than the opened aperture, while the aperiodic (noncooperative) one can achieve inversed molecular sieving under a thermodynamic mechanism.The energy barrier and structure in the nonequilibrium state are also important for flexibility and adsorption/separation. With suitable energy barriers between metastable structures, new types of framework flexibility such as aperture gating can be realized. While kinetically controlled gating flexibility is usually ignored because of the difficulty of characterization or considered as disadvantageous for separation because of the variable aperture size, it plays a critical role in most kinetic separation systems, including adsorbents conventionally regarded as rigid. With the concept of gating flexibility, the meanings of aperture and guest sizes for judging molecular sieving need to be reconsidered. Gating flexibility depends on not only the host itself but also the guest, the host-guest interaction, and the external environment such as temperature, which can be rationally tuned to achieve special adsorption/separation behaviors such as inversed temperature dependence, molecular sieving, and even inversed thermodynamic selectivity. The comprehensive understanding of the thermodynamic and kinetic bases of flexibility will give a new horizon for next-generation separation materials beyond MOFs and adsorbents.

All-solid-state potentiometric salicylic acid sensor for in-situ measurement of plant.

Using PEDOT as the conductive polymer, an innovative small-scale sensor for directly measuring salicylate ions in plants was developed, which avoided the complicated sample pretreatment of traditional analytical methods and realized the rapid detection of salicylic acid. The results demonstrate that this all-solid-state potentiometric salicylic acid sensor is easy to miniaturize, has a longer lifetime (≥1 month), is more robust, and can be directly used for the detection of salicylate ions in real samples without any additional pretreatment. The developed sensor has a good Nernst slope (63.6 ± 0.7 mV/decade), the linear range is 10-2 ~ 10-6 M, and the detection limit can reach (2.8 × 10-7 M). The selectivity, reproducibility, and stability of the sensor were evaluated. The sensor can perform stable, sensitive, and accurate in situ measurement of salicylic acid in plants, and it is an excellent tool for determining salicylic acid ions in plants in vivo.

Water-Stable Metal Azolate Frameworks Showing Interesting Flexibilities for Highly Effective Bioethanol Dehydration.

The ethanol/water separation challenge highlights the adsorption capacity/selectivity trade-off problem. We show that the target guest can serve as a gating component of the host to block the undesired guest, giving molecular sieving effect for the adsorbent possessing large pores. Two hydrophilic/water-stable metal azolate frameworks were designed to compare the effects of gating and pore-opening flexibility. Large amounts (up to 28.7 mmol g-1 ) of ethanol with fuel-grade (99.5 %+) and even higher purities (99.9999 %+) can be produced in a single adsorption process from not only 95 : 5 but also 10 : 90 ethanol/water mixtures. More interestingly, the pore-opening adsorbent possessing large pore apertures showed not only high water adsorption capacity but also exceptionally high water/ethanol selectivity characteristic of molecular sieving. Computational simulations demonstrated the critical role of guest-anchoring aperture for the guest-dominated gating process.

Coupling Ruthenium Bipyridyl and Cobalt Imidazolate Units in a Metal-Organic Framework for an Efficient Photosynthetic Overall Reaction in Diluted CO2.

Artificial photocatalytic CO2 reduction, using water as the reductant, is challenging mainly because it is difficult for multiple functional units to cooperate efficiently. Here, we show that the classic photosensitive and H2O-oxidizing ruthenium bipyridyl units and CO2-reducing cobalt imidazolate units can be incorporated into a metal-organic framework using a classic organic ligand, imidazo[4,5-f][1,10]phenanthroline. Under visible light without additional sacrificial agents and photosensitizers, the overall conversion of CO2 and H2O to CO and O2 was achieved by the multifunctional photocatalyst in the CH3CN/H2O mixed solvent with a high CO production rate of 11.2 µmol g-1 h-1 and CO selectivity of ca. 100%. Thanks to its ultramicroporous structure with moderately strong CO2 adsorption ability, the photocatalyst also exhibited high performances with CO/CH4 production rates of 5.15/0.62 and 4.26/0.20 µmol g-1 h-1 in the gas phase with pure and even diluted CO2, respectively. Photoluminescence emission spectroscopy and photoelectrochemical tests confirmed that the photosensitive and catalytic units cooperated well to give suitable photocatalytic redox potentials and fast electron-hole separation.

[Progress in the studies of prostate biopsy methods].

Prostate cancer (PCa) is one of the most common malignancies in aged males, ranking the second in the incidence of malignant tumors in men. Early diagnosis is essential, as advanced PCa is quite difficult to be managed, especially when it becomes castration-resistant or neuroendocrine PCa. Currently, the diagnosis of PCa is often based on pathology by prostate biopsy. Many recent studies focus on the impact of different biopsy methods on the diagnosis of the malignancy, but no consensus has been reached hitherto. This review summarizes various prostate biopsy methods and their latest studies.

Flexible Cuprous Triazolate Frameworks as Highly Stable and Efficient Electrocatalysts for CO2 Reduction with Tunable C2 H4 /CH4 Selectivity.

Cu-based metal-organic frameworks have attracted much attention for electrocatalytic CO2 reduction, but they are generally instable and difficult to control the product selectivity. We report flexible Cu(I) triazolate frameworks as efficient, stable, and tunable electrocatalysts for CO2 reduction to C2 H4 /CH4 . By changing the size of ligand side groups, the C2 H4 /CH4 selectivity ratio can be gradually tuned and inversed from 11.8 : 1 to 1 : 2.6, giving C2 H4 , CH4 , and hydrocarbon selectivities up to 51 %, 56 %, and 77 %, respectively. After long-term electrocatalysis, they can retain the structures/morphologies without formation of Cu-based inorganic species. Computational simulations showed that the coordination geometry of Cu(I) changed from triangular to tetrahedral to bind the reaction intermediates, and two adjacent Cu(I) cooperated for C-C coupling to form C2 H4 . Importantly, the ligand side groups controlled the catalyst flexibility by the steric hindrance mechanism, and the C2 H4 pathway is more sensitive than the CH4 one.

A Porous Coordination Polymer Showing Guest-Amplified Positive and Negative Thermal Expansion.

A solvothermal reaction of Zn(NO3)2 and 4-(1H-pyrazol-4-yl)benzoic acid (H2pba) with toluene (Tol) as the template yielded a porous coordination polymer, [Zn(pba)]·0.5Tol, possessing a three-dimensional (3D) fence-like coordination framework based on inclined two-dimensional (2D) fence-like coordination layers. By virtue of the classic deformation mode of the 2D/3D fence structures, the guest-free structure exhibits very large positive thermal expansion of 347 MK-1 and moderate negative thermal expansion of -63/-83 MK-1, which are remarkably enhanced to new records of 689 and -171/-249 MK-1, respectively, by inclusion of Tol.

A Bifunctional Coordination Polymer for Al3+ Ion Detection and its Treatment Effect on Nonalcoholic Fatty Liver Disease by Promoting Lipoxygenases and Reducing Intrahepatic Triglyceride Content.

In this study, a new Cd(II)-bearing coordination polymer with the chemical formula of {[Cd4(meda)3(dpe)4(H2O)4]·(NO3)2·2(H2O)}n (1, H2meda = 3,3'-methylenedibenzoic acid, dpe = 1,2-di(pyridin-4-yl)ethane) has been successfully prepared by reaction of Cd(NO3)·4H2O with a V-shape carboxyl ligand H2meda along with the linear dipyridine ligand dpe under the hydrothermal conditions. Due to its intensive luminescence, complex 1 could be utilized as the sensor of detecting Al3+ ion, and its detection limit is 4 × 10-6 M. Firstly, the toxicity of the compound on the normal liver cells was determined with Cell Counting Kit-8 detection kit. The triglyceride in liver cells was detected by detection kit after compound treatment and the relative expression of 15-lox and 12-lox in L02 cells was also measured by RT-PCR after compound treatment. In addition, multiple functional groups that provided by the synthesized Cd(II) complex have been studied by using molecular docking simulation for the confirmation of possible binding modes that formed between ligand and receptor.

Clinical results of arthroscopic tight fibrous band release for adult moderate-to-severe gluteal fibrosis using anterior and posterior portals: a retrospective analysis of 118 consecutive cases.

BACKGROUND: To evaluate the clinical outcomes of arthroscopic tight fibrous band release in the treatment of adult moderate-to-severe gluteal fibrosis using anterior and posterior portals during mid-term follow-up. METHODS: The data of 138 patients (58 males, 80 females) aged between 18 and 42 years (mean, 28.6 years), presenting with bilateral moderate-to-severe gluteal fibrosis (GF) from October 2013 to August 2019, was retrospectively analyzed. All patients underwent arthroscopic tight fibrous band release using anterior and posterior portals with radiofrequency energy. Under arthroscopic guidance through the posterior portal, we debrided the fatty tissue overlying the contracted band of the gluteal muscle and excised the contracted bands using a radiofrequency device introduced through the anterior portal. The pre- and post-operative gluteal muscle contracture disability (GD) scale and the patient satisfaction rate were compared to evaluate the curative effect of the operation. RESULTS: The average operation time was 18 min (range, 10-30 min) and the average blood loss was 4 ml (range, 2-10 ml) for unilateral arthroscopic release. Two cases of post-operative minimal hematomas, 2 cases of bruising and 2 cases of local subcutaneous edema were observed as early complications and were cured by conservative treatment. After surgery, all incisions healed in stage I, and no other complications such as wound infection, nerve and blood vessel injury were detected. One hundred eighteen patients were followed up for 6 to 72 months (mean, 36 months). No lateral instability of the hip was observed and all patients returned to normal gait. The degree of adduction of the hip joint in all these 118 patients was significantly improved relative to their pre-operative conditions. One hundred fifteen patients (97.5%) were able to crouch with knees close to each other after surgery. One hundred fourteen patients (96.6%) were able to cross the affected leg completely without any support. The GD scale was improved from 55.5 ± 10.6 before operation to 90.1 ± 5.2 at the last follow-up (p < 0.05). The patient satisfaction rate was 95.8%. CONCLUSION: Arthroscopic tight fibrous band release using anterior and posterior portals is minimally invasive for adult moderate-to-severe gluteal fibrosis, with a high success rate, quick recovery after surgery and reliable medium-term effect.

Intermediate-sized molecular sieving of styrene from larger and smaller analogues.

Molecular sieving can lead to ultrahigh selectivity and low regeneration energy because it completely excludes all larger molecules via a size restriction mechanism. However, it allows adsorption of all molecules smaller than the pore aperture and so separations of complicated mixtures can be hindered. Here, we report an intermediate-sized molecular sieving (iSMS) effect in a metal-organic framework (MAF-41) designed with restricted flexibility, which also exhibits superhydrophobicity and ultrahigh thermal/chemical stabilities. Single-component isotherms and computational simulations show adsorption of styrene but complete exclusion of the larger analogue ethylbenzene (because it exceeds the maximal aperture size) and smaller toluene/benzene molecules that have insufficient adsorption energy to open the cavity. Mixture adsorption experiments show a high styrene selectivity of 1,250 for an ethylbenzene/styrene mixture and 3,300 for an ethylbenzene/styrene/toluene/benzene mixture (orders of magnitude higher than previous reports). This produces styrene with a purity of 99.9%+ in a single adsorption-desorption cycle. Controlling/restricting flexibility is the key for iSMS and can be a promising strategy for discovering other exceptional properties.

Two Isostructural Flexible Porous Coordination Polymers Showing Contrasting Single-Component and Mixture Adsorption Properties for Propylene/Propane.

Solvothermal reactions of 3-(3-methylpyridin-4-yl)benzoic acid (Hmpba) with Mn(NO3)2 or Co(NO3)2 yielded isostructural porous coordination polymers, [Mn(mpba)2]·guest (MCF-56, 1·g) and [Co(mpba)2]·guest (MCF-57, 2·g), respectively. X-ray diffraction revealed that 1·g and 2·g possess similar one-dimensional ultramicroporous channels, and guest-free [Mn(mpba)2] (1') and [Co(mpba)2] (2') possess significantly and slightly contracted channels, respectively. Single-component C3H6/C3H8 adsorption isotherms and computational simulations showed the typical nonporous-to-porous structural transformations for 1', in which C3H6 exhibits a significantly lower threshold pressure, and the typical small-pore-to-large-pore structural transformations for 2', in which C3H6 exhibits a slightly lower threshold pressure. Mixture column breakthrough experiments showed that the C3H6/C3H8 separation performances of 2' are obviously better than those of 1', because the latter cannot adsorb C3H6 below the threshold pressure for pore opening, and the pore opened by C3H6 can adsorb C3H8.

A Hydrogen-Bonded yet Hydrophobic Porous Molecular Crystal for Molecular-Sieving-like Separation of Butane and Isobutane.

Porous molecular crystals sustained by hydrogen bonds and/or weaker connections are an intriguing type of adsorbents, but they rarely demonstrate efficient adsorptive separation because of poor structural robustness and tailorability. Herein, we report a porous molecular crystal based on hydrogen-bonded cyclic dinuclear AgI complex, which exhibits exceptional hydrophobicity with a water contact angle of 134°, and high chemical stability in water at pH 2-13. The seemingly rigid adsorbent shows a pore-opening or nonporous-to-porous type butane adsorption isotherm and complete exclusion of isobutane, indicating potential molecular sieving. Quantitative column breakthrough experiments show slight co-adsorption of isobutane with an experimental butane/isobutane selectivity of 23, and isobutane can be purified more efficiently than for butane. In situ powder/single-crystal X-ray diffraction and computational simulations reveal that a trivial guest-induced structural transformation plays a critical role.

In Situ Enzyme Immobilization with Oxygen-Sensitive Luminescent Metal-Organic Frameworks to Realize "All-in-One" Multifunctions.

Metal-organic frameworks (MOFs) for enzyme immobilization have already shown superior tunable and designable characteristics, however, their diverse responsive properties have rarely been exploited. In this work we integrated a responsive MOF into a MOF-enzyme composite with the purpose of designing an "all-in-one" multifunctional composite with catalytic and luminescence functions incorporated into a single particle. As a proof-of-concept, glucose oxidase (GOx) was encapsulated in situ within an oxygen (O2 )-sensitive, noble-metal-free, luminescent CuI triazolate framework (MAF-2), denoted as GOx@MAF-2. Owing to the rigid scaffold of MAF-2 and confinement effect, the GOx@MAF-2 composite showed significantly improved stability (shelf life of 60 days and heat resistance up to 80 °C) as well as good selectivity and recyclability. More importantly, owing to the O2 sensitivity of MAF-2, the GOx@MAF-2 composite exhibited a rapid and reversible response towards dissolved O2 , thereby allowing direct and ratiometric sensing of glucose without the need for chromogenic substrates, cascade enzymatic reactions, or electrode systems. High sensitivity with a detection limit of 1.4 µm glucose was achieved, and the glucose levels in human sera were accurately determined. This strategy has led to a new application for MOFs that can be facilely extended to other MOF-enzyme composites due to the multifunctionality of MOFs.

Partially Fluorinated Cu(I) Triazolate Frameworks with High Hydrophobicity, Porosity, and Luminescence Sensitivity.

Solvothermal reactions of 3-methyl-5-trifluoromethyl-1,2,4-triazole (Hfmtz) with Cu(CH3COO)2 at 120 °C in the presence of Cl- generate two partially fluorinated coordination polymers: i.e., [Cu4Cl(fmtz)3] (1 or MAF-51) and [Cu7Cl(fmtz)6] (2 or MAF-52). Single-crystal X-ray diffraction revealed 1 to have a three-dimensional (3D) nonporous structure with pcu topology consisting of 6-connected Cu4(µ4-Cl) clusters and 2 to possess a highly porous (void ratio 48%) 3D bnn network consisting of 5-connected Cu5(µ5-Cl) clusters. Benefiting from the hydrophobic pendant groups, complete coordination of the ligand N atoms, and strong M-N coordination bonds, 1 and 2 possess high water stability (exposed to water for at least 1 year) and hydrophobicity (water contact angles of 141° and 148°, respectively). The N2 sorption isotherm of activated 2 gave Langmuir/BET surface areas of 1023/848 m2 g-1 and a pore volume of 0.365 cm3 g-1. Moreover, 2 can adsorb large amounts of benzene and methanol but barely adsorb water. Both 1 and 2 show phosphorescence of Cu(I) complexes, but only that of porous 2 is sensitive to O2, showing a linear Stern-Volmer response below 1 mbar with an ultrahigh Ksv value of 5234 bar-1 and ultralow limit of detection of 1.9 ppm.

Selective Aerobic Oxidation of a Metal-Organic Framework Boosts Thermodynamic and Kinetic Propylene/Propane Selectivity.

Efficient adsorptive separation of propylene/propane (C3 H6 /C3 H8 ) is highly desired and challenging. Known strategies focus on either the thermodynamic or the kinetic mechanism. Here, we report an interesting reactivity of a metal-organic framework that improves thermodynamic and kinetic adsorption selectivity simultaneously. When the metal-organic framework is heated under oxygen flow, half of the soft methylene bridges of the organic ligands are selectively oxidized to form the more polar and rigid carbonyl bridges. Mixture breakthrough experiments showed drastic increase of C3 H6 /C3 H8 selectivity from 1.5 to 15. For comparison, the C3 H6 /C3 H8 selectivities of the best-performing metal-organic frameworks Co-MOF-74 and KAUST-7 were experimentally determined to be 6.5 and 12, respectively. Gas adsorption isotherms/kinetics, single-crystal X-ray diffraction, and computational simulations revealed that the oxidation gives additional guest recognition sites, which improve thermodynamic selectivity, and reduces the framework flexibility, which generate kinetic selectivity.

Non-3d Metal Modulation of a Cobalt Imidazolate Framework for Excellent Electrocatalytic Oxygen Evolution in Neutral Media.

Cobalt imidazolate frameworks are classical electrocatalysts for the oxygen evolution reaction (OER) but suffer from the relatively low activity. Here, a non-3d metal modulation strategy is presented for enhancing the OER activity of cobalt imidazolate frameworks. Two isomorphous frameworks [Co4 (MO4 )(eim)6 ] (M=Mo or W, Heim=2-ethylimidazole) having Co(eim)3 (MO4 ) units and high water stabilities were designed and synthesized. In different neutral media, the Mo-modulated framework coated on a glassy carbon electrode shows the best OER performances (1 mA cm-2 at an overpotential of 210 mV in CO2 -saturated 0.5 m KHCO3 electrolyte and 2/10/22 mA cm-2 at overpotential of 388/490/570 mV in phosphate buffer solution) among non-precious metal catalysts and even outperforms RuO2 . Spectroscopic measurements and computational simulations revealed that the non-3d metals modulate the electronic structure of Co for optimum reactant/product adsorption and tailor the energy of rate-determining step to a more moderate value.