Poly(vinylidene chloride)-Based Carbon with Ultrahigh Microporosity and Outstanding Performance for CH₄ and H₂ Storage and CO₂ Capture

Poly­(vinylidene chloride)-based carbon (PC) with ultrahigh microporisity was prepared by simple carbonization and KOH activation, exhibiting great potential to be superior CO₂, CH₄, and H₂ adsorbent at high pressures. The CO₂ uptake for pristine PC is highly up to 3.97 mmol/g at 25 °C and 1 bar while the activated PC exhibits a slightly lower uptake at 1 bar. However, the activated PC has an outstanding CO₂ uptake of up to 18.27 mmol/g at 25 °C and 20 bar. Gas uptakes at high pressures are proportional to the surface areas of carbons. The CH₄ uptake for the activated PC is up to 10.25 mmol/g (16.4 wt % or 147 v/v) at 25 °C and 20 bar which is in a top-ranked uptake for large surface area carbons. Furthermore, H₂ uptake on the activated PC reaches 4.85 wt % at −196 °C and 20 bar. Significantly, an exceptionally large H₂ storage capacity of up to 2.43 wt % at 1 bar was obtained, which is among the largest value reported to date for any porous adsorbents, to the best of our knowledge. The ease of preparation and large capture capacities endow this kind of carbon attractive as promising adsorbent for CH₄, H₂, and CO₂ storage

Enhanced Uptake and Selectivity of CO₂ Adsorption in a Hydrostable Metal–Organic Frameworks via Incorporating Methylol and Methyl Groups

A new methylol and methyl functionalized metal–organic frameworks (MOFs) QI-Cu has been designed and synthesized. As a variant of NOTT-101, this material exhibits excellent CO₂ uptake capacities at ambient temperature and pressure, as well as high CH₄ uptake capacities. The CO₂ uptake for QI-Cu is high, up to 4.56 mmol g^–1 at 1 bar and 293 K, which is top-ranked among MOFs for CO₂ adsorption and significantly larger than the nonfunctionalized NOTT-101 of 3.93 mmol g^–1. The enhanced isosteric heat values of CO₂ and CH₄ adsorption were also obtained for this linker functionalized MOFs. From the single-component adsorption isotherms, multicomponent adsorption was predicted using the ideal adsorbed solution theory (IAST). QI-Cu shows an improvement in adsorptive selectivity of CO₂ over CH₄ and N₂ below 1 bar. The incorporation of methylol and methyl groups also greatly improves the hydrostability of the whole framework

Fabrication of New Uranyl Phosphonates by Varying Quaternary Ammonium Cation: Synthesis, Structure, Luminescent Properties, and Single-Crystal to Single-Crystal Transformation

Four new uranyl triphosphonates, namely, [N­(CH₄)₄]­[UO₂(H₃L)]­[H₂O] (<b>1</b>), [(UO₂)_1.5(H₃L)­(H₂O)_1.5]­[H₂O] (<b>2</b>), [NBu₄]­[(UO₂)_3.5­(H₂L)₂]­[(H₂O)_4.5] (<b>3</b>), and [(UO₂)_1.5(H₃L)­(H₂O)_2.5]­[(H₂O)_2.5] (<b>4</b>), where H₆L = benzene-1,3,5-triyltris­(methylene)­triphosphonic acid, were obtained from a triphosphonate ligand in the presence of different quaternary ammonium cations. The structural characterization revealed that the introduction of quaternary ammonium cation had a major impact on the structure formation of uranyl phosphonates. Compound <b>1</b> possesses a three-dimensional anionic framework structure. Tetramethylammonium cations are accommodated in the channels, serving as counterions and structure directing agents. Compound <b>2</b> also displays a three-dimensional framework structure but is neutral, because the tetrapropylammonium cations are not involved in the crystal structure. Compound <b>3</b> has an intercalation structure; between the layers are the tetrabutylammonium cations, balancing the charge and strengthening the supramolecular structure with C–H···O interactions. No obvious uptake of N₂ and CO₂ could be observed for compound <b>2</b> due to the shrinkage of the framework and structural transformation. Compound <b>2</b> undergoes single-crystal to single-crystal transformation under vacuum, leading to the formation of compound <b>4</b>, which possesses a two-dimensional layer structure. The photophysical properties of these compounds were also investigated

Table_1_The clinical efficacy and safety of different biliary drainage in malignant obstructive jaundice: a meta-analysis.docx

BackgroundCurrently, percutaneous transhepatic cholangial drainage (PTCD) and endoscopic retrograde cholangiopancreatography (ERCP) are commonly employed in clinical practice to alleviate malignant obstructive jaundice (MOJ). Nevertheless, there lacks a consensus regarding the superiority of either method in terms of efficacy and safety.AimTo conduct a systematic evaluation of the effectiveness and safety of PTCD and ERCP in treating MOJ, and to compare the therapeutic outcomes and safety profiles of these two procedures.MethodsCNKI, VIP, Wanfang, CBM, PubMed, Web of Science, Embase, The Cochrane Library, and other databases were searched for randomized controlled trials (RCTs) on the use of PTCD or ERCP for MOJ. The search period was from the establishment of the databases to July 2023. After quality assessment and data extraction from the included studies, Meta-analysis was performed using RevMan5.3 software.ResultsA total of 21 RCTs involving 1,693 patients were included. Meta-analysis revealed that there was no significant difference in the surgical success rate between the two groups for patients with low biliary obstruction (P=0.81). For patients with high biliary obstruction, the surgical success rate of the PTCD group was higher than that of the ERCP group (P 0.05).ConclusionBoth PTCD and ERCP can efficiently alleviate biliary obstruction and enhance liver function. ERCP is effective in treating low biliary obstruction, while PTCD is more advantageous in treating high biliary obstruction.</p

Large Surface Area Ordered Porous Carbons via Nanocasting Zeolite 10X and High Performance for Hydrogen Storage Application

We report the preparation of ordered porous carbons for the first time via nanocasting zeolite 10X with an aim to evaluate their potential application for hydrogen storage. The synthesized carbons exhibit large Brunauer-Emmett-Teller surface areas in the 1300–3331 m²/g range and pore volumes up to 1.94 cm³/g with a pore size centered at 1.2 nm. The effects of different synthesis processes with pyrolysis temperature varied in the 600–800 °C range on the surface areas, and pore structures of carbons were explored. During the carbonization process, carbons derived from the liquid–gas two-step routes at around 700 °C are nongraphitic and retain the particle morphology of 10X zeolite, whereas the higher pyrolysis temperature results in some graphitic domains and hollow-shell morphologies. In contrast, carbons derived from the direct acetylene infiltration process have some incident nanoribbon or nanofiber morphologies. A considerable hydrogen storage capacity of 6.1 wt % at 77 K and 20 bar was attained for the carbon with the surface area up to 3331 m²/g, one of the top-ranked capacities ever observed for large surface area adsorbents, demonstrating their potential uses for compacting gaseous fuels of hydrogen. The hydrogen capacity is comparable to those of previously reported values on other kinds of carbon-based materials and highly dependent on the surface area and micropore volume of carbons related to the optimum pore size, therefore providing guidance for the further search of nanoporous materials for hydrogen storage

Electrocatalytic Hydrogen Evolution and Oxygen Reduction on Polyoxotungstates/Graphene Nanocomposite Multilayers

Negatively charged Pressler-type heteropolytungstate K_12.5Na_1.5[NaP₅W₃₀O₁₁₀] (P₅W₃₀) clusters and graphene oxide (GO) were constructed into polyoxotungstates/graphene (POTs/G) nanocomposite multilayer with protonated poly­(ethylenimine) (PEI) via layer-by-layer self-assembly. The growth process of (PEI/P₅W₃₀–GO)_<i>n</i> multilayer films was monitored by UV–visible spectroscopy and cyclic voltammetry. The atomic force microscopy images clearly showed the morphology of single-sheet GO in multilayer films. The UV-light irradiation of multilayers afforded reduced graphene oxide (RGO) in the multilayers. The changes in composition of C 1s in GO, W 4f in P₅W₃₀, and N 1s in PEI were detected by X-ray photoelectron spectroscopy. A possible photoreduction mechanism of GO was proposed. The electrochemical behavior of (PEI/P₅W₃₀–RGO)_<i>n</i> multilayers modified on a glassy carbon electrode at room temperature and their electrocatalytic activity toward oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER) were investigated. At a potential of −0.6 V, the multilayers clearly exhibited electrocatalytic activity for ORR via almost a four-electron reduction pathway to H₂O. A remarkable electrocatalytic HER could be detected on the (PEI/P₅W₃₀–RGO)_<i>n</i> multilayer, whereas the (PEI/P₅W₃₀–GO)_<i>n</i> multilayer did not show any HER signal in the same potential range. This study investigated and extended the application of POTs/G nanocomposites to the electrocatalysis of ORR and HER

Charge Generation and Recombination in High Fullerene Content Organic Bulk Heterojunction Solar Cells

Organic bulk heterojunction solar cells with a high fullerene content (larger than 70%) have been studied in this work. The device performances of this kind of solar cell could be tuned by adjusting the blend ratio in the active layer. An appropriate amount of p-type semiconductor in the high fullerene content active blend layer is beneficial for light absorbance and exciton dissociation. The proper energy alignment between the highest occupied molecular orbital of a p-type material and an n-type fullerene derivative has a strong influence on the exciton dissociation efficiency. In addition, the mechanism of photogenerated charge recombination in the solar cells has been identified through intensity-dependent current density–voltage (<i>J–V</i>) measurements and results show that the mechanisms governing the recombination are crucial for solar cell performance

Solvothermal Metal Metathesis on a Metal–Organic Framework with Constricted Pores and the Study of Gas Separation

Metal–organic frameworks (MOFs) with constricted pores can increase the adsorbate density of gas and facilitate effective CO₂ separation from flue gas or natural gas due to their enhanced overlapping of potential fields of the pores. Herein, an MOF with constricted pores, which was formed by narrow channels and blocks of functional groups, was fabricated from the assembly of a methyl-functionalized ligand and Zn­(II) centers (termed NPC-7-Zn). Structural analysis of the as-synthesized NPC-7-Zn reveals a series of zigzag pores with pore diameters of ∼0.7 nm, which could be favorable for CO₂ traps. For reinforcing the framework stability, a solvothermal metal metathesis on the pristine MOF NPC-7-Zn was performed, and a new Cu­(II) MOF (termed NPC-7-Cu) with an identical framework was produced. The influence of the reaction temperatures on the metal metathesis process was investigated. The results show that the constricted pores in NPC-7-Zn can induce kinetic issues that largely slow the metal metathesis process at room temperature. However, this kinetic issue can be solved by applying higher reaction temperatures. The modified MOF NPC-7-Cu exhibits significant improvements in framework stability and thus leads to a permanent porosity for this framework. The constricted pore structure enables enhanced potential fields for these pores, rendering this MOF with high adsorbate densities for CO₂ and high adsorption selectivity for a CO₂/N₂ gas mixture. The adsorption kinetic studies reveal that CH₄ has a faster diffusion rate constant than CO₂, showing a surface diffusion controlled mechanism for CO₂ and CH₄ adsorption

Solvothermal Metal Metathesis on a Metal–Organic Framework with Constricted Pores and the Study of Gas Separation

Metal–organic frameworks (MOFs) with constricted pores can increase the adsorbate density of gas and facilitate effective CO₂ separation from flue gas or natural gas due to their enhanced overlapping of potential fields of the pores. Herein, an MOF with constricted pores, which was formed by narrow channels and blocks of functional groups, was fabricated from the assembly of a methyl-functionalized ligand and Zn­(II) centers (termed NPC-7-Zn). Structural analysis of the as-synthesized NPC-7-Zn reveals a series of zigzag pores with pore diameters of ∼0.7 nm, which could be favorable for CO₂ traps. For reinforcing the framework stability, a solvothermal metal metathesis on the pristine MOF NPC-7-Zn was performed, and a new Cu­(II) MOF (termed NPC-7-Cu) with an identical framework was produced. The influence of the reaction temperatures on the metal metathesis process was investigated. The results show that the constricted pores in NPC-7-Zn can induce kinetic issues that largely slow the metal metathesis process at room temperature. However, this kinetic issue can be solved by applying higher reaction temperatures. The modified MOF NPC-7-Cu exhibits significant improvements in framework stability and thus leads to a permanent porosity for this framework. The constricted pore structure enables enhanced potential fields for these pores, rendering this MOF with high adsorbate densities for CO₂ and high adsorption selectivity for a CO₂/N₂ gas mixture. The adsorption kinetic studies reveal that CH₄ has a faster diffusion rate constant than CO₂, showing a surface diffusion controlled mechanism for CO₂ and CH₄ adsorption

Hysteretic Gas and Vapor Sorption in Flexible Interpenetrated Lanthanide-Based Metal–Organic Frameworks with Coordinated Molecular Gating via Reversible Single-Crystal-to-Single-Crystal Transformation for Enhanced Selectivity

A series of flexible 3-fold interpenetrated lanthanide-based metal organic frameworks (MOFs) with the formula [Ln­(HL)­(DMA)₂]·DMA·2H₂O, where Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, and Er, DMA = dimethylacetamide, and H₄L = 5,5′-(2,3,5,6-tetramethyl-1,4-phenylene)­bis­(methylene)­bis­(azanediyl)­diisophthalic acid, have been prepared. [Sm­(HL)­(DMA)₂]·DMA·2H₂O was studied as an exemplar of the series. The activated Sm­(HL)­(DMA)₂ framework exhibited reversible single-crystal-to-single-crystal (SCSC) structural transformations in response to adsorption and desorption of guest molecules. X-ray single crystal structural analysis showed that activation of [Sm­(HL)­(DMA)₂]·DMA·2H₂O by heat treatment to form Sm­(HL)­(DMA)₂ involves closing of 13.8 × 14.8 Å channels with coordinated DMA molecules rotating into the interior of the channels with a change from <i>trans</i> to <i>cis</i> Sm coordination and unit cell volume shrinkage of ∼20%, to a void volume of 3.5%. Solvent exchange studies with CH₂Cl₂ gave [Sm­(HL)­(DMA)₂]·2.8CH₂Cl₂ which, at 173 K, had a structure similar to that of <i>trans</i>-[Sm­(HL)­(DMA)₂]·DMA·2H₂O. CH₂Cl₂ vapor sorption on activated <i>cis</i>-[Sm­(HL)­(DMA)₂] results in gate opening, and the fully loaded structure has a similar pore volume to that of <i>trans</i>-[Sm­(HL)­(DMA)₂]·2.8CH₂Cl₂ structure at 173 K. Solvent exchange and heat treatment studies also provided evidence for intermediate framework structural phases. Structural, thermodynamic, and kinetic aspects of the molecular gating mechanism were studied. The dynamic and structural response of the endothermic gate opening process is driven by the enthalpy of adsorption, entropic effects, and Fickian diffusion along the pores produced during framework structure development thus relating the structure and function of the material. Exceptionally high CO₂ selectivity was observed at elevated pressure compared with CH₄, H₂, O₂, and N₂ due to molecular gate opening of <i>cis</i>-[Sm­(HL)­(DMA)₂] for CO₂ but not for the other gases. The CO₂ adsorption induced the structural transformation of <i>cis</i>-[Sm­(HL)­(DMA)₂] to <i>trans</i>-[Sm­(HL)­(DMA)₂], and hysteretic desorption behavior allows capture at high pressure, with storage at lower pressure