Controllable Pore Research Articles

Nickel Acetate-Assisted Graphitization of Porous Activated Carbon at Low Temperature for Supercapacitors With High Performances.

Catalytic graphitization opens a route to prepare graphitic carbon under fairly mild conditions. Biomass has been identified as a potentially attractive precursor for graphitic carbon materials. In this work, corn starch was used as carbon source to prepare hollow graphitic carbon microspheres by pyrolysis after mixing impregnation with nitrate salts, and the surface of these carbon microspheres is covered with controllable pores structure. Under optimal synthesis conditions, the prepared carbon microspheres show a uniform pore size distribution and high degree of graphitization. When tested as electrode materials for supercapacitor with organic electrolyte, the electrode exhibited a superior specific capacitance of 144.8 F g−1 at a current density of 0.1 A g−1, as well as large power density and a capacitance retention rate of 93.5% after 1,000 cycles in galvanostatic charge/discharge test at 1.0 A g−1. The synthesis extends use of the renewable nature resources and sheds light on developing new routes to design graphitic carbon microspheres.

A fractal physics-based data-driven model for water-flooding reservoir (FlowNet-fractal)

This paper proposed a fractal physics-based data-driven framework for reservoir simulation (name as FlowNet-fractal) by integrating physics-based data-driven model with fractal theory. FlowNet-fractal enables fast history matching and production prediction of water flooding reservoirs by considering the fractal characteristics of reservoir permeability and porosity. Details of FlowNet-fractal calculation were given with an oil-water two-phase flow example. In the FlowNet-fractal, transmissibility, control pore volumes (PVs), fractal mass dimension and fractal index were separately defined in each one-dimensional connection element to map reservoir properties, which more specifically reflected reservoir heterogeneity than the traditional FlowNet method. In this paper, an example of simple heterogeneous reservoir model and two actual water-flooding reservoir cases with different scales were given. The calculation results showed that the FlowNet-fractal method outperformed the FlowNet method in both the convergence speed and the accuracy of history matching. Moreover, the heterogeneity of the reservoir model was also defined by the inversed fractal mass dimension and the fractal index. • An integrated fractal-physics-based data-driven model and fractal theory are proposed in this research as the FlowNet-fractal framework for reservoir simulation. • The FlowNet-fractal approach beats the FlowNet method in terms of computing correctness, convergence speed, and historical matching effect. • Using the fractal mass dimension and fractal index, FlowNet-fractal may not only highlight reservoir heterogeneity but also significantly boost calculation rate.

One-Pot Method to Synthesize Silver Nanoparticle-Modified Bamboo-Based Carbon Aerogels for Formaldehyde Removal.

The present study demonstrated a freeze-drying-carbonization method to synthesize silver nanoparticle-modified bamboo-based carbon aerogels to remove formaldehyde. The bamboo-based carbon aerogel (BCA) has the advantages of controllable pore size and rich oxygen-containing groups, which can provide a good foundation for surface modification. BCA can greatly enhance the purification of formaldehyde by loading silver nanoparticles. The maximum adsorption capacity of 5% Ag/BCA for formaldehyde reached 42 mg/g under 25 ppm formaldehyde concentration, which is 5.25 times more than that of BCA. The relevant data were fitted by the Langmuir model and the pseudo 2nd-order model and good results were obtained, indicating that chemical absorption occurred between the carbonyl of formaldehyde and the hydroxyl of BCA. Therefore, silver nanoparticle-modified bamboo-based carbon aerogels play a positive role in the selective removal of formaldehyde. Silver nanoparticles promoted the activation of oxygen and strengthened the effect of BCA on HCHO adsorption.

Poroelastic experiments on COx claystone: Insight from the Biot's coefficient measurement with water

This paper focuses on Biot's coefficient measurement of saturated COx claystone. The tests were systematically conducted to provide clarification on its value as the available literature indicates quite erratic results from 0.26 to 1. The difficulty of this work mainly lies in the time that is necessary to stabilize each loading step (confining pressure and/or pore pressure) and also in sample preparation. Two main results were obtained: 1) Whatever the initial conditions were (confining pressure Pc amplitude, hydric state, damaged or not…), all samples exhibited a significant anisotropic swelling during the first water injection; 2) even being a transversely isotropic rock, its Biot's tensor is (quasi) isotropic thus leading to a unique coefficient “b” which is very close to 1. Such results are consistent with what was observed with gas as being the fluid to control pore pressure in partially saturated samples.

Energy Transfer in Metal-Organic Frameworks for Fluorescence Sensing.

The development of materials with outstanding performance for sensitive and selective detection of multiple analytes is essential for the development of human health and society. Luminescent metal–organic frameworks (LMOFs) have controllable surface and pore sizes and excellent optical properties. Therefore, a variety of LMOF-based sensors with diverse detection functions can be easily designed and applied. Furthermore, the introduction of energy transfer (ET) into LMOFs (ET-LMOFs) could provide a richer design concept and a much more sensitive and accurate sensing performance. In this review, we focus on the recent five years of advances in ET-LMOF-based sensing materials, with an emphasis on photochemical and photophysical mechanisms. We discuss in detail possible energy transfer processes within a MOF structure or between MOFs and guest materials. Finally, the possible sensing applications of the ET-LMOF-based sensors are highlighted.

Enhanced Inhibition of Drug-Resistant Escherichia coli by Tetracycline Hydrochloride-Loaded Multipore Mesoporous Silica Nanoparticles.

Drug-resistant bacterial infections exhibit a major threat to public health. Thus, exploring a novel antibacterial with efficient inhibition is urgently needed. Herein, this paper describes three types of MSNs (MSNs-FC2-R1, MSNs-FC2-R0.75, MSNs-FC2-R0.5) with controllable pore size (4–6 nm) and particle size (30–90 nm) that were successfully prepared. The MSNs were loaded with tetracycline hydrochloride (TCH) for effective inhibition of Escherichia coli (ATCC25922) and TCH-resistant Escherichia coli (MQ776). Results showed that the loading capacity of TCH in three types of MSNs was as high as over 500 mg/g, and the cumulative release was less than 33% in 60 h. The inhibitory rate of MSNs-FC2-R0.5 loaded with TCH against E. coli and drug-resistant E. coli reached 99.9% and 92.9% at the concentration of MIC, respectively, compared with the other two types of MSNs or free TCH. Modified MSNs in our study showed a great application for long-term bacterial growth inhibition.

A novel sintering additive system for porous mullite-bonded SiC ceramics: High mechanical performance with controllable pore structure

High strength and thermal shock resistant mullite-bonded porous SiC ceramics are essential for applications in catalyst, hot gas/solid filtration/separation fields. However, these properties were limited by the contradictory issue: higher temperature is necessary for the formation and densification of mullite bond phase, while lower temperature is preferred to avoid sever oxidation of SiC accompanied with detrimental cristobalite phase. Herein, a novel composite additive system, Al(OH)3+Y2O3+CaF2, was proposed to solve this problem for one shot. Flexural strength as high as 113 MPa (40.3 vol% porosity) was achieved for samples sintered in air, even higher than that fabricated by expensive SPS technique (103 MPa, 35.7 vol%). Critical quenching temperature reached 547 °C, around 227 °C improved. Meanwhile, additives acted as pore formers and small variation of them could effectively modify the size and shape of pores. The evolution of pore structure with additives was thoroughly evaluated and models were established for the first time. Correlations of phase composition, microstructure, porosity, pore size and shape to the performance of porous SiC were investigated. This work provides a flexible strategy to simultaneously control the mechanical performance and pore structure for low cost porous SiC ceramics.

Mechanistic study of pH effect on organic solvent nanofiltration using carboxylated covalent organic framework as a modeling and experimental platform

Covalent organic framework (COF) membranes for organic solvent nanofiltration (OSN) have attracted growing interest due to their high stability, well-defined pore size, and controllable pore functionality. In aqueous nanofiltration processes, solution pH has a significant effect on membrane permeability, selectivity, and fouling. However, our understanding of pH effects on OSN processes is still limited. Here, we present experimental and reactive force field molecular dynamics (ReaxFF MD) simulation results on the effect of pH on OSN using a well-characterized carboxylated COF (C-COF) membrane. Filtration experimental and modeling results both demonstrate that pH changes can affect solvent permeance and solute rejection dramatically. Specifically, methanol permeance decreases with the increase of NaOH and HCl concentration, respectively. When Alcian Blue dye was used as the solute in methanol, the selectivity increased from 23% to 98% when changing the feed pH from 2.2 to 10.1, respectively. While ReaxFF MD results show that C-COF solvated pore size is only marginally affected by the pH of solution, methanol diffusion is affected by the size of methanol-solvated Na+ and Cl- ions, which increase with increasing Na+ and Cl- concentrations. Solution pH change also affected solute solvation layer thicknesses and C-COF pore charges, contributing to the significant AB dye selectivity increase with pH increase. To summarize, we have shown that dramatic changes in C-COF selectivity are not anomalous in OSN, but are instead controllable by varying feed solution pH to modify solvated solute radii and surface charge.

Application of imine covalent organic frameworks in sample pretreatment

亚胺类共价有机骨架(I-COFs)是有机单体根据席夫碱(Schiff-base)反应原理缩合形成的一类新型多孔晶体有机材料。I-COFs具有骨架密度低、比表面积大、孔隙率高、单体种类丰富、孔径尺寸可控、结构可功能化、合成方法多样和物化稳定性好等优点。近年来,I-COFs已成为材料科学领域的研究前沿,并广泛用于气体吸附、存储、催化、传感、光电材料等方面。I-COFs材料优异的物理化学性能使其非常适于用作复杂样品中痕量目标物的分离富集介质,其高比表面积、高孔隙率性能赋予了它极高的吸附负载量,这些性能使得目标分析物可被高效富集;通过控制有机单体的链段长度、几何结构、掺杂元素、取代基团等方面精确调控I-COFs的孔洞结构和功能化基团,从而实现目标痕量物质的选择性富集。目前,I-COFs材料在样品前处理领域作为新型萃取介质已引起了极大关注。该文综述了近年来I-COFs材料的主要类型、合成方法及其在固相萃取、磁性固相萃取、分散固相萃取和固相微萃取方面的研究进展,同时展望了I-COFs在样品前处理领域的发展前景。

A review on the development of a porous carbon-based as modeling materials for electric double layer capacitors

Carbon electrodes are a key factor for electric double layer capacitors (EDLCs). Carbon gels have high porosity with a controllable pore structure by changing synthesis conditions and modifying preparation processing to improve the electrochemical performance of EDLCs. This review summarizes the preparation of carbon gels and their derivatives, the criteria to synthesize high surface area in each process, the development by some carbon forms, and EDLC applications. Porous carbons are also prepared as model materials by concentrating on how pore structure increases electrochemical capacitance, such as electronic and ion resistance, the tortuosity of pore channel, suitable micropore and mesopore sizes, and mesopore size distribution. This review emphasizes the significance of pore structures as the key factor to allow for the design of suitable pore structures that are suitable as the carbon electrode for EDLCs.

Cover Feature: Fractal Features of the Catalytic Performances of Bimodal Mesoporous Silica‐Supported Organocatalysts Derived from Bipyridine‐Proline for Asymmetric Aldol Reaction (Asian J. Org. Chem. 2/2022)

Heterogeneous catalysis is a promising way to developing benign processes in asymmetric aldol reaction, in which the catalytic performance can be precisely modulated by bipyridine-proline loaded catalyst. Herein, the bimodal mesoporous silicas could provide controlled pore channels and suitable modified surfaces for reactants and organic catalysts. Therefore, their reactivity and selectivity, as well as recyclability potential could be improved. Besides, the fractal features of the heterogeneous catalysts were elucidated in-depth by SAXS method. More information can be found in the Full Paper by Jihong Sun et al.

Process optimization of porous Al2O3 filter via layered extrusion forming

ABSTRACT Porous ceramic filters have great potential in alloy casting fields to reduce casting defects such as reoxidation inclusions and pores. However, the uniform shape and size distribution is critically restricted by the conventional manufacturing process. Herein, an additive manufacturing method, layered extrusion forming, was applied for rapidly preparing porous Al2O3 ceramic filters with controllable pores morphology and overall application performance, including the flexural strength and total porosity. This paper firstly investigated the characteristics of the extruded filaments, then optimized the process parameters (the filling rate, extrusion nozzle diameter, and filling angle) of layered extrusion forming through an orthogonal experiment and a response surface analysis. Finally, based on the flexural strength, total porosity, and linear shrinkage, the optimum sintering temperature was determined to achieve the proper formation of porous Al2O3 ceramic filters with adequate strength and porosity properties. Results show that when prepared at the 20% filling rate, the 0.34 mm extrusion nozzle diameter, the 0/90/45/-45° filling angle, and sintered at 1400°C, the porous Al2O3 ceramic filter sample possesses excellent comprehensive performance. Under the optimized parameters, the flexural strength 14.35MPa, the total porosity is 67.6%, the macroscopic porosity is 53.40%, and the linear shrinkage rate is 2.51%.

An Electroactive Filter with Tunable Porosity Based on Glycolated Polythiophene

The porosity of filters is typically fixed; thus, complex purification processes require application of multiple specialized filters. In contrast, smart filters with controllable and tunable properties enable dynamic separation in a single setup. Herein, an electroactive filter with controllable pore size is demonstrated. The electroactive filter is based on a metal mesh coated with a polythiophene polymer with ethylene glycol sidechains (p(g3T2)) that exhibit unprecedented voltage‐driven volume changes. By optimizing the polymer coating on the mesh, controllable porosity during electrochemical addressing is achieved. The pores reversibly open and close, with a dynamic range of more than 95%, corresponding to over 30 μm change of pores’ widths. Furthermore, the pores’ widths could be defined by applied potential with a 10 μm resolution. From among hundreds of pores from different samples, about 90% of the pores could be closed completely, while only less than 1% are inactive. Finally, the electroactive filter is used to control the flow of a dye, highlighting the potential for flow control and smart filtration applications.

Single Molecule DNA Analysis Based on Atomic-Controllable Nanopores in Covalent Organic Frameworks.

We explored the application of two-dimensional covalent organic frameworks (2D COFs) in single molecule DNA analysis. Two ultrathin COF nanosheets were exfoliated with pore sizes of 1.1 nm (COF-1.1) and 1.3 nm (COF-1.3) and covered closely on a quartz nanopipette with an orifice of 20 ± 5 nm. COF nanopores exhibited high size selectivity for fluorescent dyes and DNA molecules. The transport of long (calf thymus DNA) and short (DNA-80) DNA molecules through the COF nanopores was studied. Because of the strong interaction between DNA bases and the organic backbones of COFs, the DNA-80 was transported through the COF-1.1 nanopore at a speed of 270 μs/base, which is the slowest speed ever observed compared with 2D inorganic nanomaterials. This study shows that the COF nanosheet can work individually as a nanopore monomer with controllable pore size like its biological counterparts.

One-step synergistic optimization of hierarchical pore topology and nitrogen dopants in activated coke for efficient catalytic oxidation of nitric oxide

Carbon-catalyzed oxidation represents a promising strategy for nitrogen oxide emission control. Here, we report a new strategy to simultaneously optimize the pore topology and doping environment of activated coke (AC) catalyst through one-step catalytic activation process with nitrogen resource in-situ participation. Dynamic experiments of nitric oxide catalytic oxidation using the prepared activated cokes with controllable pore configurations and doping environment firstly demonstrate that hierarchical pore configuration and nitrogen functional groups can synergistically improve catalytic oxidation activity. Especially, nitrogen-doped hierarchical porous AC catalyst exhibits the highest conversion efficiency (above 70%). Based on density functional theory calculations in combination with control experiments using pyridinic nitrogen and quaternary nitrogen-dominant catalysts, a new activity descriptor of electrophilic Fukui function is proposed and quaternary nitrogen is thereby identified to be the optimal nitrogen doping configuration towards nitric oxide catalytic oxidation. This work provides new insights into the synergistic role of pore topology and nitrogen doping in nitric oxide low-temperature oxidation, giving guidance for designing high-performance carbocatalyst.

Reconstruction of three-dimension digital rock guided by prior information with a combination of InfoGAN and style-based GAN

In digital rock physics, the study of physical parameters and flow characteristics of reservoirs requires a wealth of three-dimension digital rock samples. However, traditional physical methods of obtaining digital rock are expensive, and numerical reconstruction method cannot obtain a reasonable pore structure for complex rock. Recently, generative adversarial networks (GANs) have proven to be a successful method for reconstructing pore-scale models, but the reconstructed large-size digital rocks look unreasonable due to the lack of sufficient consideration of multi-scale information fusion and it takes a lot of computational resources and time to build the model. Hence, we proposed a combination of InfoGAN and style-based GAN guided by prior information (CISGAN) to reconstruct more controllable and reasonable digital rock models using small set of samples. Porosity distribution as prior information is added into latent space to control pore distribution, and a classifier Q is set in discriminator to ensure the porosity is limited to reasonable range. Multi-scale information is applied each layer by style transfer and used to optimize the background information, pore structure, and micro information of model for multi-scale fusion to produce more reasonable and natural digital rock. Simple-structure sandstone and complex-structure carbonate are implemented to test the reconstruction ability of network. The result shows that synthetic sample has high consistency on pore-throat geometry and connectivity, and the CISGAN can produce natural and user-specified digital rock samples. And the CISGAN will provide more reasonable and various type samples for intelligent parameter prediction of digital rock.

PPy nanotubes-enabled in-situ heating nanofibrous composite membrane for solar-driven membrane distillation

• A superhydrophobic photothermal composite membrane was demonstrated. • PDMS binder enhanced the structural stability and hydrophobicity of dual-layer membrane. • The PPy NTs/PVDF nanofibrous composite membrane showed outstanding solar-driven DCMD performance. Solar-driven membrane distillation is an emerging desalination technology with low energy consumption and efficient vapor collection, but the low vapor flux and limited efficiency hinders its practical application. Here, we demonstrated an innovative photothermal composite membrane by depositing polypyrrole nanotubes (PPy NTs) as functional coating layer onto an electrospun poly (vinylidene fluoride) (PVDF) nanofibrous support layer via vacuum filtration stabilized by adhesive polydimethylsiloxane (PDMS). According to the proportional relationship between the fibrous materials diameter and the pore size, the large-scale surface gaps between adjacent nanofibrous could be replaced by smaller pores from the PPy NTs layer on the PVDF substrate. The PDMS with low surface energy was used as an adhesive to in-situ solder the loose PPy NTs together as well as to enhance the adhesion between the PPy layer and the PVDF substrate to form an integrated and robust dual-layer composite membrane with superhydrophobicity, high porosity and controllable pore size. By exploring the optimal match of PPy loading and PDMS concentration, the solar-to-thermal performance and structural stability could be significantly improved. With 1 sun irradiation, the selected composite membrane thus showed a high-water vapor flux of 1.3 kg/(m 2 ·h) and a photothermal conversion efficiency of 81.6%, specially, the membranes maintained stable permeate conductivity during the 10 h solar-driven DCMD seawater desalination test. These results indicated that the photothermal dual-layer superhydrophobic composite membranes has promising potential for desalination with the help of sustainable energy sources such as sunlight.

Synthesis of mesoporous SiO2 nanoparticles and toxicity assessment in early life stages of zebrafish

Mesoporous nanoparticles (MNPs) have attracted great interest in the biomedical applications as reliable drug carriers for cancer treatment. They have significant advantages over the traditional drug carriers due to high surface area, controllable pore size, large pore volume, easy adjustment of the inner and outer surfaces, and also, high drug loading capacity. This work has focused on the synthesis of mesoporous silicon dioxide nanoparticles (MNPs) with different pore volumes and their toxicity effects on zebrafish. The structural and morphological analyses of MNPs were carried out through XRD and HRTEM, functional groups have been identified by FTIR and N2 adsorption/desorption isotherm and the pore size distribution was determined by BET analysis. The maximum pore volume of 1.5 cm3/g and a pore size of 8.0 nm, were reported. Survival percentage of zebrafish was reported to be above 85%.

Advances and challenges in the development of nanosheet membranes

Abstract The development of highly efficient separation membranes utilizing emerging materials with controllable pore size and minimized thickness could greatly enhance the broad applications of membrane-based technologies. Having this perspective, many studies on the incorporation of nanosheets in membrane fabrication have been conducted, and strong interest in this area has grown over the past decade. This article reviews the development of nanosheet membranes focusing on two-dimensional materials as a continuous phase, due to their promising properties, such as atomic or nanoscale thickness and large lateral dimensions, to achieve improved performance compared to their discontinuous counterparts. Material characteristics and strategies to process nanosheet materials into separation membranes are reviewed, followed by discussions on the membrane performances in diverse applications. The review concludes with a discussion of remaining challenges and future outlook for nanosheet membrane technologies.

Ring structure characterization of nanoporous carbon materials prepared by thermal conversion of fullerenes: Insights from ReaxFF molecular dynamics simulations

It is challenging to prepare porous carbon materials with controllable pore sizes via the thermal conversion of fullerenes. Experimental reports have indicated that the conversion temperature and carbon source are critical factors that determine the morphology of the thermal conversion products, but the microstructure evolution and its relationship with experimental parameters are largely unknown. Here, we investigate the pyrolysis and graphitization mechanism of fullerenes during thermal conversion using reactive molecular dynamics (ReaxFF-MD) simulations. By analyzing changes in the intermediates and products formed during thermal conversion, the underlying dependence of the pyrolysis and graphitization of fullerenes on the temperature and carbon sources are revealed. We found that a higher temperature greatly accelerated the pyrolysis of fullerenes and produced an enormous variety of porous carbon products. The simulations revealed that seven-membered (7-M) carbon rings were formed between adjacent fullerene clusters during the early stage of pyrolysis. The effects observed during thermal conversion were closely related to changes in the number of 7-M carbon rings, allowing 7-M carbon rings to be used as an indicator of the pyrolysis and graphitization processes. In experiments, this knowledge can inspire researchers to obtain porous carbon materials by regulating the - formation of ring structures. This provides a new direction for the design and development of porous carbon materials with controllable morphologies and better performance.