Tunable Mesopore Research Articles

Trimodal Hierarchical Porous Metal–Organic Frameworks with Tunable Mesoporous Core–Shell Architectures

Trimodal Hierarchical Porous Metal–Organic Frameworks with Tunable Mesoporous Core–Shell Architectures

Bagasse heavy ash-derived Zn-loaded porous silica with tunable mesopores: Effect of monomodal and bimodal pores on VOCs adsorption

Bagasse heavy ash-derived Zn-loaded porous silica with tunable mesopores: Effect of monomodal and bimodal pores on VOCs adsorption

Efficient Fabrication of Hierarchical Porous Carbon Fibers with Tunable Mesopores from Discarded Aramid for Supercapacitors

Efficient Fabrication of Hierarchical Porous Carbon Fibers with Tunable Mesopores from Discarded Aramid for Supercapacitors

One-Pot Mechanochemical Synthesis of Carbons with High Microporosity and Ordered Mesopores for CO2 Uptake at Ambient Conditions.

Mechanochemical synthesis of ordered mesoporous carbons with tunable mesopores and well-developed irregular microporosity is investigated. This synthesis was carried out by the self-assembly of ecofriendly chemicals such as tannin and glyoxal used as carbon precursors, and triblock copolymer as a soft templating agent. The structural properties of the resulting carbons were tailored by using different block copolymers (Pluronic F127, and P123) as soft templates. The various weight ratios of tannin and block copolymer were employed to tune the textural properties of these carbons. The tannin: Pluronic F127 ratios (1:0.75, 1:1, 1:1.1) gave the ordered mesoporous carbons among a wide variety of the samples studied. The ordered mesoporosity was not observed in the case of Pluronic P123 templated mesoporous carbons. The CO2-activated carbon samples obtained for both Pluronic templates showed a high specific surface area (close to 900 m2/g), large pore volume (about 0.6-0.7 cm3g-1), narrow pore size distribution, and high CO2 uptake of about 3.0 mmol g-1 at 1 bar pressure and ambient temperature.

Metal–Organic Framework‐Derived N‐Doped Carbon with Controllable Mesopore Sizes for Low‐Pt Fuel Cells

AbstractMesoporous structure of carbon materials plays an important role in electrocatalyst design. Constructing carbon supports with tunable mesopores has long been a challenge. Herein, the elaborate regulation of mesopores in N‐doped carbon materials is reported by pyrolyzing energetic metal‐triazolate (MET) frameworks with different particle sizes and at different ramp rates. Higher thermal transfer rates brought about by smaller particle size and higher ramp rate lead to more violent decomposition with a large number of gases producing, which in turn result in larger mesopores in the derivatives. Consequently, a series of N‐doped carbon materials with controllable mesopores are obtained. As a proof‐of‐concept, ultrafine Pt nanoparticles are enveloped inside these mesopores to acquire high‐performance electrocatalysts for oxygen reduction reaction. The optimized catalyst achieves high mass activity of 1.52 A mgPt−1 at 0.9 ViR‐free and peak power density of 0.8 W cm−2 (H2‐Air) with an ultralow Pt loading of 0.05 mgPt cm−2 at cathode in fuel cells, highlighting the great advantages of MET‐derived carbon materials with controllable mesopores in the preparation of advanced electrocatalysts.

Enhanced Catalytic Oxidation of Toluene over Hierarchical Pt/Y Zeolite

The development of efficient Pt-supported zeolite catalysts with tunable micro/mesopore structures for the removal of volatile organic compounds (VOCs) presents a major challenge. Herein, hierarchical Pt/Y zeolites with tunable mesopores are fabricated by varying the etching time before the surfactant-templated crystal rearrangement method and used as catalyst supports for VOC oxidation. The hierarchical Pt/Y zeolites provided an excellent environment for Pt nanoparticle loading with abundant accessible acidic sites. The catalytic performance of the obtained hierarchical Pt/Y zeolites is analyzed using toluene oxidation, with the modified zeolites exhibiting improved catalytic activities. The hierarchical Pt/Y zeolites exhibited higher catalytic toluene oxidation activities than non-hierarchical Pt/Y zeolites. Pt/Y-6h demonstrated the highest catalytic toluene oxidation activity of the prepared catalysts, with a T90 of 149 °C, reaction rate of 1.15 × 10−7 mol gcat−1 s−1, turnover frequency of 1.20 × 10−2 s−1, and an apparent activation energy of 66.5 kJ mol−1 at 60,000 mL g−1 h−1 at a toluene concentration of 1000 ppm. This study will facilitate the fine-tuning of hierarchically porous materials to improve material properties and achieve higher catalytic performance toward VOC oxidation.

Construction of hierarchically porous metal-organic framework particle by a facile MOF-template strategy

Increasing the mass diffusion efficiency is a major challenge in the realm of metal-organic frameworks (MOFs). Construction of hierarchically porous, typically microporous MOF adsorbents or catalysts is crucial for enhancing both mass transfer and molecular accessibility. Many strategies have been proposed for the synthesis of hierarchically porous MOFs (HP-MOFs), with some striking results. In this paper, we proposed a facile and versatile strategy, termed the MOF-Template strategy, for fabricating hierarchical pores in MOF particle. The highly controlled crystalline sizes and morphologies of the unstable Cu-MOFs Cu3(BTC)2 and Cu(Qc)2 have been exploited in their utilization as sacrificial agents by uniformly dispersing them during the shaping process of ZIF-8. Through a facile treatment with alkaline solution, tunable mesopores and macropores could be easily introduced in the shaped ZIF-8 spheres. This strategy could effectively improve the adsorption kinetics and separation productivity of MOF materials while maintaining high mechanical stability, offering promising prospects for industrial application.

Specific Screening of Prostate Cancer Individuals Using an Enzyme-Assisted Substrate Sensing Platform Based on Hierarchical MOFs with Tunable Mesopore Size.

Rapid and specific identification of tumor metabolic markers is of great significance. Herein, a convenient, reliable and specific strategy was proposed to screen prostate cancer (PCa) individuals through indirectly quantifying sarcosine, an early indicator of PCa, in the clinical urine samples. The success roots in the rational design of a cascade response model, which takes integrated sarcosine oxidase (SOX) as a specific recognition unit and oxygen-sensitive molecule as a signal reporter. The newly developed hierarchical mesoporous Zr-based metal-organic frameworks with continuously tunable mesopore size ensure the synergetic work of the SOX and response unit spatially separated in their neighboring mesoporous and microporous domains, respectively. The large mesopore up to 12.1 nm not only greatly enhances the loading capacity of SOX but also spares enough space for the free diffusion of sarcosine. On this basis, the probe is competent to specifically check out the tiny concentration change of sarcosine in the urine sample between PCa patients and healthy humans. Such a concept of enzyme-assisted substrate sensing could be simply extended by altering the type of immobilized enzymes, hopefully setting a guideline for the rational design of multiple probes to quantify specific biomarkers in complex biological samples.

Bimodally-porous alumina with tunable mesopore and macropore for efficient organic adsorbents

Since it is of great importance to remove aqueous pollutants for distributing clean water, the adsorption of toxic chemicals on solid adsorbent has been the most practical technique. As one of the widely-accepted design for an adsorbent, hierarchical channel or structurally-connected large and small pore networks take several advantages for application in catalysis and adsorption in liquid or gaseous environment. Mesoporous networks can provide size and shape selectivity for foreign molecule, while macropores can reduce transport limitations and increase the accessibility to the active sites. In this study, we adopted alumina as an adsorbent of organic pollutants due to its easy structural engineering in crystal structure, textural properties, and morphology. As an efficient organic adsorbent, bimodally-porous alumina (BPA) was synthesized to contain mesopores and macropores, which were able to be structured in a separately-controllable manner via solvent-deficient hydrolysis method. The macropores are formed by using polymer beads as a sacrificial template. Additionally, the mesoporous framework is structured through controlling hydrolysis reaction between aluminum alkoxides and water. After calcination, the BPA was pelletized into cylinder or coin shapes for recycling adsorbents without separation and collection steps. We examined the systematic characteristics of the BPA samples, which are associated with the optimal adsorption capability in terms of surface conditions and structural/morphological difference.

Mesoporous carbon aerogel with tunable porosity as the catalyst support for enhanced proton-exchange membrane fuel cell performance

Proton-exchange membrane fuel cells (PEMFCs) are considered to be one of the most promising clean technologies to mitigate climate change, air pollution, and energy crisis. Although PEMFCs have been intensively investigated over the past five decades, the relatively low current density, high cost, and poor durability remain as obstacles to full commercialization. In this study, we present the development and the application of a porosity-tunable carbon aerogel (CA) as an alternative to the carbon support in the PEMFC to overcome its technical barriers. CA demonstrates highly tunable mesopore volume and surface area. The N2 isotherm with non-localized density functional theory analysis shows the optimized CA had extremely high mesopore volume, which was 4.26 times larger than the traditional carbon support (i.e., Vulcan XC-72R). Transmission electron microscopy shows a better catalyst (i.e., platinum nanoparticles) distribution on the CA support. This even distribution of platinum nanoparticles significantly enhances the catalyst utilization of the electrodes in our cyclic voltammetry analysis. It also contributes up to a 713% higher specific power density in our fuel cell testing. The standard accelerated stress tests exhibit that CA has excellent durability compared with the conventional carbon support. Thus, the mesoporous CA provides an efficient and durable alternative to existing carbon material as a catalyst support in PEMFCs.

Facile approach for the synthesis of spherical mesoporous silica nanoparticles from sodium silicate

We developed a facile synthetic method for the preparation of spherical mesoporous silica nanoparticles from a sodium silicate solution. Spherical mesoporous silica with an overall size of several hundreds of nanometers was obtained through a simple sol–gel process using acetic acid and polyethylene glycol (PEG) as a pH adjuster and morphology directing agent, respectively. In this method, PEG is an essential component that affects the shape of silica particles and that leads to the formation of mesopores on silica. Additionally, the size of the mesopores could be easily controlled by changing the reaction temperature. Thus, we successfully synthesized spherical silica nanoparticles with tunable mesopores ranging from 3 to 40 nm. This synthetic method can be valuable in developing customized porous silica nanoparticles using an inexpensive silica resource.

Organic solvent-free fabrication of mesoporous polymer monolith from miscible PLLA/PMMA blend

The fabrication of monoliths by environment-friendly methods without organic solvents remains a challenging task. In this study, we successfully produced mesoporous polymer monoliths by selective hydrolysis degradation of miscible poly(-L-lactic acid) (PLLA)/poly(methyl methacrylate) (PMMA) blends without any organic solvents. 50 to 90 wt% of PLLA blend ratios were tested. We found that freeze-dried was effective to prevent a shrinkage of monoliths. With increaser of PLLA weight fraction, porosity, mode pore diameter, and pore geometry could be controlled from 17 to 52%, 7.1–32 nm, and mainly cylindrical to spherical, respectively. Further, a comprehensive model based on volume balance and surface area equivalence successfully predicted mode pore size. The reported organic solvent-free fabrication of mesoporous polymer monoliths might enable tunable mesopore properties through only changing mechanical blending of miscible polymers.

Multiscale Colloidal Assembly of Silica Nanoparticles into Microspheres with Tunable Mesopores

AbstractColloidal assembly of silica (nano)particles is a powerful method to design functional materials across multiple length scales. Although this method has enabled the fabrication of a wide range of silica‐based materials, attempts to design and synthesize porous materials with a high level of tuneability and control over pore dimensions have remained relatively unsuccessful. Here, the colloidal assembly of silica nanoparticles into mesoporous silica microspheres (MSMs) is reported using a discrete set of silica sols within the confinement of a water‐in‐oil emulsion system. By studying the independent manipulation of different assembly parameters during the sol–gel process, a design strategy is outlined to synthesize MSMs with excellent reproducibility and independent control over pore size and overall porosity, which does not require additional ageing or post‐treatment steps to reach pore sizes as large as 50 nm. The strategy presented here can provide the necessary tools for the microstructural design of the next generation of tailor‐made silica microspheres for use in separation applications and beyond.

Mesoporous N-doped carbon nanofibers with surface nanocavities for enhanced catalytic activity toward oxygen reduction reaction

Mesoporous N-doped carbon (m-N-Carbon) nanofibers with controlled numerous surface nanocavities as efficient oxygen reduction reaction electrocatalysts have been fabricated through carbonization polyaniline (PANI) nanofibers decorated with different sizes of SiO2 nanoparticles. The prepared m-N-Carbon nanofibers possess tunable mesopores, high surface area and desired nitrogen moieties. Among these, the sample m-N-Carbon (M-900) exhibits the highest electrocatalytic performance with high onset potential (0.941), half-wave potential (0.713 V), superior catalytic stability with slightly attenuated after 20000-s continuous operation and well tolerance to methanol. The enhanced electrocatalytic activities are associated with high-nitrogen content and the rational design of mesoporous structure N-Carbon nanofibers, which are contributed to the mass/electron transfer and exposure of active sites.

Controllable Preparation of Monodisperse Mesoporous Silica from Microspheres to Microcapsules and Catalytic Loading of Au Nanoparticles.

A unique structural transition from pomegranate-like monodisperse mesoporous silica microspheres (M-MSMs) with tunable mesopores to mesoporous silica microcapsules has been reported. The unique evolution occurred together with varying the cross-linking degrees (CLDs) of templates. Herein, using monodisperse sulfonated cross-linked polystyrene (S-CLPS) as templates, S-CLPS/SiO2 composite microspheres were synthesized by the sol-gel method. Subsequently, the templates were removed by calcination to obtain the M-MSMs or microcapsules. The pore sizes of M-MSMs could be tailored from 3.2 to 7.4 nm by facilely varying the CLDs from 0.5 to 20%. Interestingly, mesoporous silica microcapsules were gradually formed when the CLDs were beyond 20%. Meanwhile, the specific surface area also could be adjusted by this strategy without hardly affecting the monodispersity, and the specific surface area increased to 391.9 m2/g. Significantly, Au@M-MSM was prepared by supporting Au nanoparticles (NPs) on M-MSM and used as nanocatalysts to reduce 4-nitrophenol (4-NP). The ultrathin shell and interconnected three-dimensional (3D) porous structure of M-MSMs can increase the mass transfer and protect the Au NPs from leakage, which reveals high recyclability and high conversion (>95%) after 10 regeneration-catalysis cycles. This approach provides a nanotechnology platform for the preparation of mesoporous silica materials with different microstructures, which will have enormous potential in practical applications involving different molecular sizes.

Hierarchically porous UiO-66 with tunable mesopores and oxygen vacancies for enhanced arsenic removal

An ultrahigh arsenic uptake capacity was achieved using a hierarchically porous UiO-66 with tunable mesopores and active sites.

An Assembly and Interfacial Templating Route to Carbon Supercapacitors with Simultaneously Tailored Meso- and Microstructures.

The development of facile strategies for simultaneously tailoring robust pore hierarchy and integrated microstructures in carbonaceous materials is critical for the efficient multiscale control of fluid, molecular/ionic, and charge transport in applications spanning separations, catalysis, and energy storage. Here, we synthesize three-dimensionally ordered hierarchically porous carbon powders by the assembly of glucose with silica nanoparticle building blocks of sacrificial NP-crystalline templates. Such template-replica coassembly offers an attractive alternative to conventional nanocasting by circumventing the need for sequential template preformation and infiltration-based replication. In addition, interfacial templating leads to hierarchically structured carbons with tunable mesopore volumes (as high as 5.8 cm3/g). Beyond mesostructuring, we identify the template-replica interface as a potentially versatile but generally unexploited handle for tailoring the sp2 hybridized carbon content in the porous replicas under mild carbonization conditions and without specific chemical activation or catalytic graphitization. This multiscale (meso-micro) templating offered by a single template expands the potential versatility of nanocasting for the hierarchical structuring of replica materials. Application of the resulting carbons as electrochemical double layer capacitors demonstrates the combined benefit of simultaneously tailored pore hierarchy and tuned microstructures upon ion and charge transport, respectively, yielding supercapacitors achieving specific capacitance as high as 275 F/g in the aqueous electrolyte (H2SO4) and retention of 90% up to a current density of 10 A/g.

The preparation of hierarchical Pt/ZSM-5 catalysts and their performance for toluene catalytic combustion

Abstract The hierarchical ZSM-5 zeolite with tunable mesopore volume was successfully prepared by adjusting the synthesis condition and used as the support for dispersing Pt. The mesopore volume of as-prepared hierarchical ZSM-5 zeolite showed the monotonous and positive effect for the Pt dispersion. The toluene catalytic combustion was used to evaluate the performance of as-prepared Pt supported catalysts. The results demonstrated the high performance for catalytic toluene combustion over hierarchical Pt/mZSM-5 catalysts compared with Pt/ZSM-5. In addition, the hierarchical Pt/mZSM-5 catalysts showed better reactant molecular diffusion according to the results of toluene dynamic adsorption experiments. Among all the as-prepared catalysts, Pt/mZSM-5-A8 exhibited best activity that T90 was 159 °C and Ea was 40.0 kJ/mol at 500 ppm toluene and 80,000 mL/(g · h), and the catalyst showed high stability and catalytic activity after catalytic testing for 20 h at 155 °C, which implied a promising catalyst for practical application.

Dual-active-sites design of CoSx anchored on nitrogen-doped carbon with tunable mesopore enables efficient Bi-Functional oxygen catalysis for ultra-stable zinc-air batteries

Developing highly efficient oxygen electrode is particular important in the application of electrochemical energy conversion and storage technologies. In this work, we report the synthesis of highly dispersed CoSx nanocrystals anchored on N-doped mesoporous carbon (CoSx@NMC) network electrode. CoSx@NMC, derived from Fe/Co dual tuning nitrogen/sulfur-containing polymer as carbon precursor, manifests discrete dual-active-sites endowing excellent bifunctional catalytic activity toward both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). The zinc-air battery system assembled from this CoSx@NMC electrode exhibits an open circuit voltage of 1.44V (vs. Zn/Zn+) and a peak power density of 269.7 mW cm−2. Notably, it exhibits a super stability in the galvanostatic discharge of 5 mA and 50 mA, and the voltage could be maintained stable at 1.25V over 90h galvanostatic discharge. Rechargeable zinc-air battery delivers an excellent cycling stability beyond 1288 charge/discharge cycles. The superior electrochemical catalytic properties for ORR/OER are attributed to the strongly coupled pyridine-N, graphitic-N and nanoscale CoSx, which can promote the simultaneous exposure of both OER and ORR active centres. Further investigations reveal that the microstructure of the mesoporous carbon might experience a structural remodeling during the charge/discharge process.

Modulation versus Templating: Fine‐Tuning of Hierarchally Porous PCN‐250 Using Fatty Acids To Engineer Guest Adsorption

AbstractModulation and templating are two synthetic techniques that have garnered significant attention over the last several years for the preparation of hierarchically porous metal–organic frameworks (HP‐MOFs). In this study, by using fatty acids with different lengths and concentrations as dual‐functional modulators/templates, we were able to obtain HP‐MOFs with tunable mesopores that exhibit different pore diameters and locations. We found that the length and concentration of the fatty acids can determine if micelle formation occurs, which in turn dictates the porosity of the resulting HP‐MOFs. The HP‐MOFs with different mesopores differed in their performance in gas uptake and dye adsorption, and the structure–performance relationships were ascribed to the pore diameters and locations. This approach could provide a potentially universal method to efficiently introduce hierarchal mesopores into existing microporous MOF adsorbents with tunable properties.