Manipulation Of Pore Size Research Articles

Defect-enabling zirconium-based metal-organic frameworks for energy and environmental remediation applications.

This comprehensive review explores the diverse applications of defective zirconium-based metal-organic frameworks (Zr-MOFs) in energy and environmental remediation. Zr-MOFs have gained significant attention due to their unique properties, and deliberate introduction of defects further enhances their functionality. The review encompasses several areas where defective Zr-MOFs exhibit promise, including environmental remediation, detoxification of chemical warfare agents, photocatalytic energy conversions, and electrochemical applications. Defects play a pivotal role by creating open sites within the framework, facilitating effective adsorption and remediation of pollutants. They also contribute to the catalytic activity of Zr-MOFs, enabling efficient energy conversion processes such as hydrogen production and CO2 reduction. The review underscores the importance of defect manipulation, including control over their distribution and type, to optimize the performance of Zr-MOFs. Through tailored defect engineering and precise selection of functional groups, researchers can enhance the selectivity and efficiency of Zr-MOFs for specific applications. Additionally, pore size manipulation influences the adsorption capacity and transport properties of Zr-MOFs, further expanding their potential in environmental remediation and energy conversion. Defective Zr-MOFs exhibit remarkable stability and synthetic versatility, making them suitable for diverse environmental conditions and allowing for the introduction of missing linkers, cluster defects, or post-synthetic modifications to precisely tailor their properties. Overall, this review highlights the promising prospects of defective Zr-MOFs in addressing energy and environmental challenges, positioning them as versatile tools for sustainable solutions and paving the way for advancements in various sectors toward a cleaner and more sustainable future.

Metal-organic framework-based nanomaterials for CO2 storage: A review.

The increasing recognition of the impact of CO2 emissions as a global concern, directly linked to the rise in global temperature, has raised significant attention. Carbon capture and storage, particularly in association with adsorbents, has occurred as a pivotal approach to address this pressing issue. Large surface area, high porosity, and abundant adsorption sites make metal-organic frameworks (MOFs) promising contenders for CO2 uptake. This review commences by discussing recent advancements in MOFs with diverse adsorption sites, encompassing open metal sites and Lewis basic centers. Next, diverse strategies aimed at enhancing CO2 adsorption capabilities are presented, including pore size manipulation, post-synthetic modifications, and composite formation. Finally, the extant challenges and anticipated prospects pertaining to the development of MOF-based nanomaterials for CO2 storage are described.

The membrane perspective of uraemic toxins: which ones should, or can, be removed?

ABSTRACTInformed decision-making is paramount to the improvement of dialysis therapies and patient outcomes. A cornerstone of delivery of optimal dialysis therapy is to delineate which substances (uraemic retention solutes or ‘uraemic toxins’) contribute to the condition of uraemia in terms of deleterious biochemical effects they may exert. Thereafter, decisions can be made as to which of the accumulated compounds need to be targeted for removal and by which strategies. For haemodialysis (HD), the non-selectivity of membranes is sometimes considered a limitation. Yet, considering that dozens of substances with potential toxicity need to be eliminated, and targeting removal of individual toxins explicitly is not recommended, current dialysis membranes enable elimination of several molecules of a broad size range within a single therapy session. However, because HD solute removal is based on size-exclusion principles, i.e. the size of the substances to be removed relative to the mean size of the ‘pores’ of the membrane, only a limited degree of selectivity of removal is possible. Removal of unwanted substances during HD needs to be weighed against the unavoidable loss of substances that are recognized to be necessary for bodily functions and physiology. In striving to improve the efficiency of HD by increasing the porosity of membranes, there is a greater potential for the loss of substances that are of benefit. Based on this elementary trade-off and availability of recent guidance on the relative toxicity of substances retained in uraemia, we propose a new evidence-linked uraemic toxin elimination (ELUTE) approach whereby only those clusters of substances for which there is a sufficient body of evidence linking them to deleterious biological effects need to be targeted for removal. Our approach involves correlating the physical properties of retention solutes (deemed to express toxicity) with key determinants of membranes and separation processes. Our analysis revealed that in attempting to remove the relatively small number of ‘larger’ substances graded as having only moderate toxicity, uncontrolled (and efficient) removal of several useful compounds would take place simultaneously and may compromise the well-being or outcomes of patients. The bulk of the uraemic toxin load comprises uraemic toxins below <30 000 Da and are adequately removed by standard membranes. Further, removal of a few difficult-to-remove-by-dialysis (protein-bound) compounds that express toxicity cannot be achieved by manipulation of pore size alone. The trade-off between the benefits of effective removal of the bulk of the uraemic toxin load and risks (increased loss of useful substances) associated with targeting the removal of a few larger substances in ‘high-efficiency’ HD treatment strategies needs to be recognized and better understood. The removability during HD of substances, be they toxic, inert or beneficial, needs be revised to establish the pros and cons of current dialytic elimination strategies.

Gate-Embedding Strategy for Pore Size Manipulation on Stainless Steel Mesh: Toward Highly Efficient Water-in-Oil Nanoemulsions Separation

Separation of water-in-oil nanoemulsions is of great significance but difficult. In this work, using a facile brush-painting method, a paste containing PDMS, graphite, TiO2 and ethyl cellulose was coated on a low-mesh-number stainless steel mesh, forming hierarchical micro/nanostructures and endowing the mesh with excellent superhydrophobicity. Meanwhile, the coating regulated the original pores of the stainless steel mesh, toward a gate-embedding effect, giving rise to the formation of suitable micropores for separating water-in-oil nanoemulsions. The separation efficiencies for various nanoemulsions were larger than 99.9% with the residual droplets smaller than 8 nm, showing outstanding separation ability. Furthermore, the wettability of the as-prepared mesh possessed good resistance to acidic, alkaline, salty, organic solvents, and UV light-exposed environments. Even if the mesh was abraded by sandpaper, its separation capability was almost totally maintained. The findings in the present work provide a...

Nano-porous shape memory membrane: Fabrication based on double bicontinuous structures in ternary blend and pore-size manipulation by macroscopic deformation

Nano-pore size is the key factor to determine the performance of porous membrane in various applications. The programmable and continuous manipulation of it remains as a great challenge. In this work, nano-porous shape memory polymer (SMP) membrane has been fabricated successfully in ternary blend of PVDF, PBSU and random copolymer (BMG) based on the special interface interaction and complicated phase behaviors among them. On one hand, phase separation takes place, producing bicontinuous structures with the characteristic size of microns including BMG rich phase and PVDF/PBSU mixed phase. The former provides shape memory effect in which cross-linked points and network play the roles of shape fixed phase and recovery phase respectively; on the other hand, exclusion of PBSU during crystallization of PVDF contributes to bicontinuous structures in nanoscale. The removal of PBSU based on double bicontinuous structures results in the interconnected nano-pores. The obtained nano-porous PVDF/BMG composite membranes possess not only shape memory performance, but also the interpenetrated channels. The pore size has been manipulated successfully by means of biaxial tension based on the proportional deformation in macro- and micro-scales. Our results provide a new strategy for the fabrication of nano-porous SMPs and the manipulation of pore size in them.

Influence of Metal–Organic Framework Porosity on Hydrogen Generation from Nanoconfined Ammonia Borane

Hydrogen released from chemical hydride ammonia borane (AB, NH3BH3) can be greatly improved when AB is confined in metal–organic frameworks (MOFs), showing reduced decomposition temperature and suppressed unwanted byproducts. However, it is still debatable whether the mechanism of improved AB dehydrogenation is due to catalysis or nanosize. In this research, selected MOFs (IRMOF-1, IRMOF-10, UiO-66, UiO-67, and MIL-53(Al)) were chosen to explore both catalytic effect of the metal clusters and the manipulation of pore size for nanoconfinement by variations in ligand length. When AB particle size was restricted by the controlled micropores of MOFs, we observed that the decomposition temperature was not correlated to the MOF catalytic environment, but inversely proportional to the reciprocal of the particle size. The results correspond well with the derived thermodynamic model for AB decomposition considering surface tension of nanoparticles.

Improvement of endothelial progenitor outgrowth cell (EPOC)-mediated vascularization in gelatin-based hydrogels through pore size manipulation

This study reveals that the optimal pore size for hydrogel vascularization in vitro and in vivo is different. The middle pore size supported best differentiation of EPOCs and thus best hydrogel vascularization in vitro, while vascularization in vivo was promoted best in hydrogels with the large pore size due to the increased vascular tissue invasion. These results highlight the difference between in vitro and in vivo culture conditions and indicate that pore sizes shall be designed for in vitro and in vivo hydrogel vascularization respectively. Pore sizes for hydrogel vascularization in vitro shall be middle ones and pore sizes for hydrogel vascularization in vivo shall be large ones.

Effect of post-polymerization anion-exchange on the rejection of uncharged aqueous solutes in nanoporous, ionic, lyotropic liquid crystal polymer membranes

The selectivity of a bicontinuous cubic, lyotropic liquid crystal (LLC) polymer nanofiltration membrane containing uniform cationic nanopores was manipulated via anion-exchange at the pore wall by soaking the fabricated membranes in aqueous salt solutions. Monovalent organosulfonate anions of various sizes were completely exchanged as the counterion at the pore walls to explore the impact of anion size on uncharged molecular solute rejection and water permeance. It was found that larger organosulfonate anions associated at the pore walls induced a higher rejection of uncharged solutes and a lower water permeance. The change in selectivity of the nanopores was described quantitatively through the calculation of the effective pore radius. The effective pore radius in these modified membranes was found to vary from 0.9±0.2 to 0.55±0.08nm depending on the resident organosulfonate counterion, demonstrating sub-1-nm resolution in pore size manipulation. An empirical model was used to demonstrate that physicochemical properties (molecular volume and hydrophobicity) of the resident counterion correlate with the observed solute rejection, suggesting that the counterion can be chosen to target a desired membrane performance. The ability to manipulate uniform, nm-sized pores with sub-1-nm resolution via simple anion-exchange offers a new avenue to tailor nanofiltration membrane performance.

Surface and pore structure modification of ordered mesoporous carbons via a chemical oxidation approach

For practical applications, the surface of porous carbon materials usually need to be modified/tailored according to specific requirements, for instance in order to improve their hydrophilicity or their interaction with catalytic species. In this contribution we report a detailed study on surface and structure modification of the recently developed ordered mesoporous carbons (OMCs) via a liquid-phase chemical oxidation approach. The structure and surface evolution of OMCs like CMK-5 and CMK-3 have been investigated using nitric acid with varying concentrations, at different oxidation temperatures and for different oxidation periods. The physical parameters as well as the chemical nature of the modifications were investigated with low-temperature nitrogen adsorption, FTIR, TG-MS, TEM, XPS and XRD analysis. After oxidation, the surface of OMCs has a high-concentration of oxygen-containing groups. The presence of carboxylic functional groups on the carbon surface was confirmed by FTIR and XPS analyses. As compared to CMK-5, CMK-3 carbon is structurally more stable during the oxidation treatment. In addition, controlled surface functionalization and pore size manipulation can also be achieved by an esterification reaction between the surface carboxyl groups and 1-butanol. The pore size of the modified carbons was decreased by about ∼1–1.2 nm.

Surface Functionalization and Pore Size Manipulation for Carbons of Ordered Structure

Covalent functionalization and pore size manipulation were successfully achieved on ordered mesoporous carbons, by using a method in which diazonium compounds were in-situ generated and reacted with the carbon surface. Aryl groups substituted on the 4-poisiton (Ar−R, R = chlorine, ester, and alkyl) were covalently attached to the surface of hexagonally structured carbon, which was synthesized using ordered silica SBA-15 as template. The presence of these functional groups on the modified carbons was confirmed with Fourier transform infrared spectroscopy, thermogravimetric analysis, electron microscopy, and nitrogen adsorption. A relatively high grafting density of ∼1.5 μmol/m2 was achieved. Chemical modification considerably changed the pore width from 3.0 nm for the unmodified samples to ∼1.4 nm for modified samples, while the primary hexagonal structure and the unit parameter of ordered mesoporous carbon were retained after attachment of surface functionalities.

THE USE OF ADSORBENTS IN THE REMOVAL OF CYTOKINES

Inflammation is an essential host reaction to infection, however over-stimulation of inflammatory pathways can lead to septic shock, acute liver failure and multiple organ failure (MOF). These conditions are characterised by an increase in the production of cytokines such as TNF-α, IL-1β and IL-6. The removal of these inflammatory mediators or their regulation may help treat these conditions. Various methods have been used to reduce levels of circulating cytokines including haemofiltration and haemoperfusion although these techniques have generally been shown to offer limited clinical benefit. However it has been shown that some adsorbents may offer an efficient alternative for the removal of cytokines from the circulation of patients suffering from sepsis (1) This study investigated the potential of a number of alternative carbon and resin based adsorbents for the removal of cytokines and the degree to which adsorption can be increased by the manipulation of pore size and surface chemistry. The adsorbents used in the experiments reported here contained macropores (>50nm), mesopores (2–50nm) and micropores (<2nm) that provide high surface area and rapid access to the internal surface, together with specific functional groups (OH or sulphonic acid) that may impart a degree of selectivity. Test solutions were prepared in a 0.1% BSA Tyrode buffer with final cytokine concentrations ranging from (0 pg.mL−1 to 1000 pg.mL−1). Solutions (15mLs) were incubated at 25°C and shaken, (100 rpm) with 0.5g of each adsorbent for 6 hours. Aliquots of solution taken at various time points were analysed using ELISA kits (IDS Ltd). Concentrations of free cytokine were calculated with reference to standard curves and used to calculate relative adsorption capacities. The results suggested that both the manipulation of pore size and functional group associated with the adsorbents can be used to increase the removal of cytokines from protein solutions. The data suggest that the adsorbents used in this study may provide a suitable therapeutic aid in the treatment of sepsis.

Stepwise functionalization of mesoporous crystalline silica materials

Novel properties have been achieved in mesoporous crystalline silica materials by organic functionalization. In this study, localized functionalization and bifunctionalization of silica MCM-41 was attempted through the stepwise post-synthesis silylation. When MCM-41 was treated with various silylating agents for 6 hours before template removal, change in pore size only was observed without any change in surface area and pore volume. MCM-41 was difunctionalized with both decyl groups on edges of pores and methyl groups on inner surfaces of pores. Capillary condensation of water took place at higher relative pressure in MCM-41 with decyl groups on edges than in unsilylated MCM-41, whereas hydrophobic property was observed in MCM-41 which were difunctionalized with decyl groups on edges of pores and with methyl groups on inner surfaces of pores. This study shows that the manipulation of pore size and functionality with/without any change in surface area and pore volume and the combination of two different functionalities could be achieved in MCM-41 through the stepwise functionalization.