Mesoporous Framework Research Articles

Mesoporous carbon framework supported Fe-Cu-Mn oxides as an efficient peroxymonosulfate catalyst for the control of harmful algal blooms: Synergism of Fe-Cu-Mn and role of mesoporous carbon

Few studies have focused on the advanced oxidation processes (AOPs) based on heterogeneous catalysis to control harmful algal blooms (HABs). Herein, a mesoporous carbon framework supported Fe-Cu-Mn oxides (MnFe2O4/CuO; FCMT) was synthesized via calcination of cost-effective metal-polyphenol coordination polymers for peroxymonosulfate (PMS) activation to eliminating Microcystis aeruginosa and algal organic matters (AOMs). >99% of algae were removed at low FCMT and PMS dosages in the FCMT/PMS within 120 min. The FCMT/PMS system removed algae effectively over extensive pH (3.0–9.0) and algal density (OD680 = 0.05–0.4) ranges. Although FCMT/PMS-induced oxidative stress damaged cell membranes, over 50% of the dissolved organic carbon and 54% of microcystins were eliminated, avoiding serious secondary pollution caused by cell lysis. Algal removal by the FCMT/PMS system involved pathways associated with both free radicals and non-free radicals, with the dominant reactive oxygen species being O2− and 1O2. Synergy between Fe, Mn, and Cu promoted the elimination of algae and AOMs. Mn found to be the primary active site on the FCMT surface, while Fe(III) was cooperated with Mn by acting as the main adsorption site. The mesoporous carbon allowed uniform spatial distribution of the nanosized Fe-Cu-Mn oxides as well as modulating the direction of reactive oxygen species generation by the metals. In conclusion, the proposed heterogeneous advanced oxidation process using the FCMT/PMS system is highly potential in the control of HABs.

Spatially confined protein assembly in hierarchical mesoporous metal-organic framework

Immobilization of biomolecules into porous materials could lead to significantly enhanced performance in terms of stability towards harsh reaction conditions and easier separation for their reuse. Metal-Organic Frameworks (MOFs), offering unique structural features, have emerged as a promising platform for immobilizing large biomolecules. Although many indirect methods have been used to investigate the immobilized biomolecules for diverse applications, understanding their spatial arrangement in the pores of MOFs is still preliminary due to the difficulties in directly monitoring their conformations. To gain insights into the spatial arrangement of biomolecules within the nanopores. We used in situ small-angle neutron scattering (SANS) to probe deuterated green fluorescent protein (d-GFP) entrapped in a mesoporous MOF. Our work revealed that GFP molecules are spatially arranged in adjacent nanosized cavities of MOF-919 to form “assembly” through adsorbate-adsorbate interactions across pore apertures. Our findings, therefore, lay a crucial foundation for the identification of proteins structural basics under confinement environment of MOFs.

Nanoconfinement-Guided Construction of Nanozymes for Determining H2 O2 Produced by Sonication.

Nanomaterials with enzyme-like activities, termed as nanozymes, have found wide applications in various fields. It has been a long-term aim to rationally design and synthesize highly active nanozymes and thus to further improve their application performance. Guided by the nanoconfinement effect, we confine cytochrome c (Cyt c) within a mesoporous metal-organic framework (MOF), PCN-222 nanoparticle (NP), forming a protein/MOF hybrid nanozyme, termed as Cyt c@PCN-222 NP. The confined Cyt c exhibits around 3-4-fold higher peroxidase-like activity than free Cyt c. Due to the increase in the activity of Cyt c, the Cyt c@PCN-222 NPs exhibit a quite low limit of detection (≈0.13 μM) towards H2 O2 . Sonication-induced H2 O2 formation in water by using a lab-quipped ultrasonic cleaner can be sensitively probed, which suggests that H2 O2 -sensitive materials should be carefully handled during the utilization of ultrasonic equipment. We speculate that this nanoconfinement strategy can broaden our synthetic methodology for the rational design of nanozymes.

Nonradical activation of peroxydisulfate over Fe/N doped mesoporous carbon for selective removal of organic pollutant

Mesoporous carbon materials are promising catalysts for peroxydisulfate (PDS) activation for degrading aqueous organic pollutants but limited by the intrinsic inertness. Herein, co-doping of iron and nitrogen into the mesoporous carbon framework was performed via thermal conversion of metal-polyphenol coordination polymers (Fe-TA) to synthesize Fe/N co-doped mesoporous carbon for efficient PDS activation. Owing to the large surface area, high graphitization degree and defective configurations, the Fe/N co-doped mesoporous carbon (Fe/N-MCs) exhibited superior catalytic performance toward the degradation of organic pollutants. Electron paramagnetic resonance tests, chemical quenching experiments, electrochemical analysis and spectra measurements revealed that the degradation of organic pollutants over the Fe/N-MCs followed a nonradical oxidation pathway based on electron transfer process. Graphite nitrogen and hydroxyl (C-OH) groups on the defective edges of Fe/N-MCs were proved to be possible active sites for PDS activation. PDS catalyzed by the Fe/N-MCs exhibited strong anti-interference capability to surrounding inorganic ions (such as Cl–, CO32–, NO3– and SO42–) and natural organic matters, making it a promising candidate for the degradation of organic pollutants. This work provides a new prospect for developing highly active mesoporous carbon materials via heteroatom doping for PDS activation for wastewater decontamination.

Visible Light‐Driven Degradation of Trichloroethylene in Aqueous Phase with Vanadium‐Doped TiO2 Photocatalysts

The development of photocatalyzed water remediation strategies using visible (solar) light to mineralize volatile chlorinated organic compounds (VCOCs) is a long standing, not yet fully achieved goal. Herewith, a facile route is presented to synthesize vanadium‐doped TiO2 photocatalysts using a one‐step hydrothermal method. Different characterization methods are employed to investigate the physicochemical properties of as‐prepared V‐doped TiO2 samples, indicating the mixed phases of anatase, rutile, and brookite in the crystal structure addition to the mesoporous framework. The nature of the vanadium species at the TiO2 surface is assessed by X‐ray photoelectron and emission spectroscopy. The aerobic photodegradation of a common VCOC, trichloroethylene, using V‐doped catalysts is demonstrated to be much more effectively than with undoped TiO2. Importantly, the herein described V‐doped photocatalysts show high activity both under ultraviolett and visible light irradiation. Moreover, these V‐doped TiO2 photocatalysts are robust under the reaction conditions, being recyclable for at least four consecutive runs without any activity loss.

Metal Node Control of Brønsted Acidity in Heterobimetallic Titanium-Organic Frameworks.

Compared to indirect framework modification, synthetic control of cluster composition can be used to gain direct access to catalytic activities exclusive of specific metal combinations. We demonstrate this concept by testing the aminolysis of epoxides with a family of isostructural mesoporous frameworks featuring five combinations of homometallic and heterobimetallic metal-oxo trimers (Fe3, Ti3, TiFe2, TiCo2, and TiNi2). Only TiFe2 nodes display activities comparable to benchmark catalysts based on grafting of strong acids, which here originate from the combination of Lewis Ti4+ and Brønsted Fe3+-OH acid sites. The applicability of MUV-101(Fe) to the synthesis of β-amino alcohols is demonstrated with a scope that also includes the gram scale synthesis of propranolol, a natural β-blocker listed as an essential medicine by the World Health Organization, with excellent yield and selectivity.

Protein-directed synthesis of ZIF-8 functionalized with a polymer as core-shell drug coatings with antibacterial and anti-inflammatory properties.

We developed a strategy to use lysozyme (Lys) as a template to produce mesoporous zeolitic imidazolate framework (ZIF-8) structures under physiological conditions. Thereafter, an amphiphilic triblock copolymer, PEG-PPG-PEG, was used to form protective core-shell ZIF-8 nanocomposite coatings to protect the encapsulated drug epigallocatechin-3-gallate (EGCG), to achieve notable antibacterial properties against E. coli, S. aureus and MRSA strains. Moreover, nanocomposites exhibited anti-inflammatory activity by counteracting the secretion of cytokines in THP-1 macrophages.

A mesoporous Zr-based metal-organic framework driven by the assembly of an octatopic linker.

Metal-organic frameworks (MOFs) based on high-connected nets are generally very attractive due to their combined robustness and porosity. Here, we describe the synthesis of BCN-348, a new high-connected Zr-MOF built from an 8-connected (8-c) cubic Zr-oxocluster and an 8-c organic linker. BCN-348 contains a minimal edge-transitive 3,4,8-c eps net, and combines mesoporosity with thermal and hydrolytic stability. Encouraging results from preliminary studies on its use as a catalyst for hydrolysis of a nerve-agent simulant suggest its potential as an agent for detoxification of chemical weapons and other pernicious compounds.

Dye encapsulation and one-pot synthesis of microporous-mesoporous zeolitic imidazolate frameworks for CO2 sorption and adenosine triphosphate biosensing.

One-pot co-precipitation of target molecules e.g. organic dyes and the synthesis of a crystal containing microporous-mesoporous regimes of zeolitic imidazolate frameworks-8 (ZIF-8) are reported. The synthesis method can be used for cationic (rhodamine B (RhB), methylene blue (MB)), and anionic (methyl blue (MeB)) dyes. The crystal growth of the ZIF-8 crystals takes place via an intermediate phase of zinc hydroxyl nitrate (Zn5(OH)8(NO3)2) nanosheets that enabled the adsorption of the target molecules i.e., RhB, MB, and MeB into their layers. The dye molecules play a role during crystal formation. The successful encapsulation of the dye molecules was proved via diffuse reflectance spectroscopy (DRS) and electrochemical measurements e.g., cyclic voltammetry (CV), linear sweep voltammetry (LSV), and electrochemical impedance spectroscopy (EIS). The materials were investigated for carbon dioxide (CO2) adsorption and adenosine triphosphate (ATP) biosensing. ZIF-8, RhB@ZIF-8, MB@ZIF-8, and MeB@ZIF-8 offered CO2 adsorption capacities of 0.80, 0.84, 0.85, and 0.53 mmol g-1, respectively. The encapsulated cationic molecules improved the adsorption performance compared to anionic molecules inside the crystal. The materials were also tested as a fluorescent probe for ATP biosensing. The simple synthesis procedure offered new materials with tunable surface properties and the potential for multi-functional applications.

Template-free synthesis of mesoporous and amorphous transition metal phosphate materials.

We present how mesoporosity can be engineered in transition metal phosphate (TMPs) materials in a template-free manner. The method involves the transformation of a precursor metal phosphate phase, called M-struvite (NH4MPO4·6H2O, M = Mg2+, Ni2+, Co2+, NixCo1-x2+). It relies on the thermal decomposition of crystalline M-struvite precursors to an amorphous and simultaneously mesoporous phase, which forms during degassing of NH3 and H2O. The temporal evolution of mesoporous frameworks and the response of the metal coordination environment were followed by in situ and ex situ scattering and diffraction, as well as X-ray spectroscopy. Despite sharing the same precursor struvite structure, different amorphous and mesoporous structures were obtained depending on the involved transition metal. We highlight the systematic differences in absolute surface area, pore shape, pore size, and phase transitions depending on the metal cation present in the analogous M-struvites. The amorphous structures of thermally decomposed Mg-, Ni- and NixCo1-x-struvites exhibit high surface areas and pore volumes (240 m2 g-1 and 0.32 cm-3 g-1 for Mg and 90 m2 g-1 and 0.13 cm-3 g-1 for Ni). We propose that the low-cost, environmentally friendly M-struvites could be obtained as recycling products from industrial and agricultural wastewaters. These waste products could be then upcycled into mesoporous TMPs through a simple thermal treatment for further application, for instance in (electro)catalysis.

Synthesis of reverse-selective nanoporous ultrafiltration membranes using dual phase separations of ionic liquid and Poly(ethylene glycol) from the gelating urea-linked covalent network

Many membranes with various pore structures have been studied for size-based selective filtration and separation. However, one exhibiting reverse size selectivity has rarely been reported. Here, we present a facile synthesis of a hierarchically nanoporous covalent framework (NCF) membranes using concurrent phase separation and gelation of the mixtures of a urea-linked network (UN) sol, poly (ethylene glycol) (PEG), and ionic liquid (IL). Subsequent solvent extraction of the dual porogens, i.e., PEG and IL, from the ternary blend gave a hierarchically nanoporous structure consisting of a continuous macropore running across a continuous mesoporous framework. The structure formation was accounted for by the primary separation of the IL-rich phase, followed by the secondary separation of the PEG domain from the continuous UN skeleton. The porosity and pore distribution of the membrane was varied by adjusting the composition of the PEG/IL/UN mixture. The hierarchical nanoporosity provided a reverse size selectivity for the ultrafiltration of proteins and polymers, promising potential applications in membrane-based protein purification or chromatography.

Fabrication of CuMn2O4/Co3O4 nanocomposite heterojunctions for efficacious visible light-induced degradation of antibiotics

The synthesis and design of heterojunction nanocomposites with remarkable photocatalytic performance remains a challenge. In this work, the fabrication of CuMn2O4/Co3O4 nanocomposite heterojunctions has been addressed for efficacious visible-light-induced degradation of tetracycline (TC). A facile sol-gel strategy with soft template assistance was utilized to synthesize mesoporous Co3O4 frameworks and then CuMn2O4 NPs were impregnated to obtain mesoporous CuMn2O4/Co3O4 nanocomposites. TEM images of CuMn2O4/Co3O4 nanocomposite revealed a homogeneous shape with a particle size of 10 nm. The degradation efficiency of CuMn2O4/Co3O4 nanocomposites exhibited significant enhancement and achieved 100% within 75 min. The 9%CuMn2O4/Co3O4 photocatalyst exhibited the highest TC degradation ability, which was enhanced 1.6 times that of pure Co3O4 NPs, and its rate constant was up to 2.35-times compared with the pure Co3O4 NPs. The photocatalytic ability of CuMn2O4/Co3O4 nanocomposites was significantly promoted due to their construction of heterojunction, the synergistic effect between CuMn2O4 and Co3O4, the enlarged surface area, strengthened effective charge mobility and narrowed bandgap energy. The CuMn2O4/Co3O4 nanocomposite was reusable and quite stable during the TC photodegradation process, even after five times repeatedly. This work shows research ideas and technical approaches for the photodegradation of antibiotics during the construction of heterojunction nanocomposites.

Ni nanoparticles in situ embedment in 3D ordered macro-/mesoporous carbon framework as efficient microwave absorption and infrared stealth materials

The development of high-performance and multi-modal stealth materials remains a challenge. Herein, nickel nanoparticles embedded in three-dimensionally ordered macro-/mesoporous carbon framework (Ni/OMMC) was fabricated using a facile dual-template approach to achieve efficient microwave absorption and multi-functions. It is found that the carbonization temperature in the preparation process of Ni/OMMC has significant influence on the electromagnetic properties of samples. The optimized microwave absorption performance was achieved by adjusting the calcination temperature to 900 °C. It shows that the minimum reflection loss (RLmin) for Ni/OMMC900 reaches −43.6 dB at 5.0 GHz with a thickness of only 2.0 mm, and effective absorption bandwidth of 5.6 GHz at 1.0 mm with the ultra-low filling ratio of only 3%. Its excellent microwave absorption performance may be attributed to enhanced conductive loss, polarization relaxation and magnetic loss, and impedance matching, which result from magnetic/conductive multi-component synergy and the unique 3D interconnected hierarchically porous structure. Additionally, Ni/OMMC900 exhibits good thermal insulation and infrared stealth functions.

Amino-Functionalized Ionic-Liquid-Grafted Covalent Organic Frameworks for High-Efficiency CO2Capture and Conversion

Rationally integrating desired functional components into a composite material can endow the tailored function to achieve the corresponding purpose. This is the first case where a series of [AeImBr]X%-TAPT-COFs (X = 0, 17, 33, 50, 67, 83, 100) were fabricated by chemically integrating the amino-functionalized imidazole ionic liquid (NH2-IL) onto channel walls of mesoporous covalent organic framework materials ([HO]X%-TAPT-COFs). By virtue of the polar groups (amino groups) and abundant imidazole cations of NH2-IL and its microporous nature, the obtained [AeImBr]X%-TAPT-COFs exhibit higher CO2 capture activity than [HO]X%-TAPT-COFs. Correspondingly, the CO2 equilibrium capture capacity increases from 62.6 to 117.4 mg/g, which is crucial to the storage of enough CO2 around the catalytic active sites. Additionally, the synergistic effect of -NH2 and Br- in NH2-IL can also improve the cycloaddition reaction rate. The characteristics of [AeImBr]X%-TAPT-COFs contribute to the efficient generation of cyclic carbonate through heterogeneously catalyzing CO2-epoxide cycloaddition without any solvents and cocatalysts. Specifically, [AeImBr]83%-TAPT-COF has a CO2 equilibrium capture capacity of 117.4 mg/g and cyclochloroallyl carbonate yield of 99.1%. As a result of the use of the chemical grafting method, [AeImBr]X%-TAPT-COFs possess excellent stability and cycle life. The equilibrium capture capacity and cyclochloroallyl carbonate yield reach 112.7 mg CO2/g adsorbent and 95.0% at the eighth cycle.

Acid-Resistant Mesoporous Metal-Organic Frameworks as Carriers for Targeted Hypoglycemic Peptide Delivery: Peptide Encapsulation, Release, and Bioactivity.

Oral administration of bioactive peptides with α-glucosidase inhibitory activities is a promising strategy for diabetes mellitus. The wheat germ peptide Leu-Asp-Leu-Gln-Arg (LDLQR) has been previously proven to inhibit the activity of α-glucosidase efficiently. However, it is still difficult to transport the peptide to the intestine completely due to the harsh condition of the stomach. Herein, an acid-resistant zirconium-based metal-organic framework, NU-1000, was used to immobilize LDLQR with a high encapsulation capacity (92.72%) and encapsulation efficiency (44.08%) in only 10 min. The in vitro release results showed that the acid-stable NU-1000 not only effectively protected LDLQR from degradation in the presence of stomach acid and pepsin effectively but also ensured the release of encapsulated LDLQR under simulated intestinal conditions. Furthermore, LDLQR@NU-1000 could slow down the elevated blood sugar caused by maltose in mice and the area under blood sugar curve decreased by almost 20% when compared with the control group. The inflammatory factor (IL-1β, IL-6) in vivo and cell growth in vitro were almost the same between NU-1000 treatment and normal control groups. This study indicates NU-1000 is a promising vehicle for targeted peptide-based bioactive delivery to the small intestine.

Waxberry‐Shaped Ordered Mesoporous P‐TiO2−x Microspheres as High‐Performance Cathodes for Lithium–Sulfur Batteries

As a candidate for a new generation of inexpensive and high‐performance energy storage systems, lithium–sulfur (Li–S) batteries have attracted widespread research. However, the development and application of Li–S batteries are limited by severe polysulfide dissolution and slow reaction kinetics. Herein, a type of ordered mesoporous P‐TiO2−x microsphere with a waxberry‐like shape as the sulfur host material for Li–S batteries is put forward, which combines the radially arranged mesoporous structure with oxygen defects in the mesoporous framework. In addition, the introduction of phosphorus impurities greatly improves the conductivity of the sulfur electrode, enhances electron mobility, and promotes the interaction between the sulfur species and P‐TiO2−x microspheres. Finally, S/P‐TiO2−x cathodes have achieved a high capacity of 1174.9 mAh g−1 at 0.2C and stable cycling (the average capacity attenuation is only 0.086% per cycle at 1C after 600 cycles).

Preparation of mesoporous poly(fullerene oxide) framework by thermal [3 + 2] cycloadditions and its application as a semiconductor photocatalyst

We report the formation of an interconnected, three-dimensional, mesoporous polymeric fullerene oxide framework via thermal [3 + 2] cyclo-additions of monomeric C60 and fullerene oxides (C60On), formed upon thermal decomposition of C60Br24, causing the eliminations of bromine atoms in an oxygen atmosphere at an elevated temperature of 200 °C. The newly formed mesoporous fullerene oxide framework is found to be a low bandgap semiconductor capable of acting as a photocatalyst similar to graphitic C3N4. The sunlight-assisted photocatalytic degradation of the methylene blue dye is demonstrated. To have a better understanding of the mechanism of the [3 + 2] cyclo-additions of monomeric C60 and fullerene oxides, a theoretical investigation has been carried out and the energetics of the reaction C60O + C60 → C120O is calculated.

Mesoporous waffle-like N-doped carbon with embedded Co nanoparticles for efficiently electrocatalytic oxygen reduction and evolution

Rational design and facile preparation of high-performance carbon-based eletrocatalysts for both oxygen reduction and evolution reactions (ORR and OER) is crucial for practical applications of rechargeable zinc-air batteries. Inspired by the fact that the metallic Co catalysis on the formation of carbon nanotubes (CNTs), this work develops a facial compression-pyrolysis route to synthesize a mesoporous waffle-like N-doped carbon framework with embedded Co nanoparticles (Co@pNC) using a Co metal–organic framework and melamine as precursors. The unique porous waffle-like carbon framework is built up of interwoven N-doped CNTs and graphene nanosheets, which offers abundant catalytic-active sites and rapid diffusion channels for intermediates and electrolyte. The optimized Co@pNC shows excellent bifunctional ORR/OER electrocatalytic activity in alkaline media with a half-wave potential (E1/2) of 0.85 V for ORR and a small potential gap of 0.70 V between ORR E1/2 and OER potential at 10 mA cm−2. Its assembled battery exhibits a peak power density up to 150.3 mW cm−2, an energy density of 928 Wh kgZn-1 and superb rate capability. It highlights a facile component and architecture strategy to design high-performance carbon-based eletrocatalysts.

Highly selective epoxidation of styrene at ambient temperature under photo-assisted condition over bimetallic Eu and Ti-doped amino-functionalized mesoporous molecular sieve

Mesoporous molecular sieves silica materials had been functionalized employing 3-aminopropyltriethoxysilane as the surface decoration agent by a post-synthesis method and Eu and Ti with different loading ratio were synchronously anchored on amino-functionalized silica framework by incipient wetness impregnation method, respectively. The structures of the synthesized samples were evaluated by means of X-ray diffraction, Fourier transform infrared spectroscopy, ultraviolet-visible spectra, scanning electron microscope, transmission electron microscope, X-ray photoelectron spectroscopy and solid-state 29Si magic angle spinning nuclear magnetic resonance spectra. The results revealed that the highly ordered mesoporous two dimensional hexagonal structure and the mesoporous channel structure were well preserved and isolated tetrahedral surface Eu3+ and isolated [TiO4] or [HOTiO3] species were found to be grafted and highly dispersed in the amino-functionalized mesoporous framework. A significant enhancement in selectivity and conversion for the photocatalytic epoxidation of styrene has been achieved by synergistic effect based on surface ligand effect and electron density effect between Eu3+ and Ti4+ species on amino-functionalized mesoporous silica framework. The factors associated with the conversion of styrene and selectivity to styrene oxide such as the solvent, metal loading, the amount of NaOH, H2O2/Styrene, the amount of catalyst and reaction time were also investigated in details. The desired selectivity (84%) to styrene oxide and excellent conversion (32%) of styrene for the photocatalytic epoxidation of styrene with turnover frequency of 3.1 × 10−4s−1 were obtained using aqueous H2O2 as an oxidant in the presence of acetonitrile solvent under ambient temperature.

Polystyrene spheres-templated mesoporous carbonous frameworks implanted with cobalt nanoparticles for highly efficient electrochemical nitrate reduction to ammonia

Electrocatalytic nitrate reduction reaction (eNO3RR) to ammonia (NH3) provides an intriguing approach for both environmental denitrification and sustainable NH3 synthesis. Herein, we report the fabrication of hierarchically mesoporous Co nanoparticles decorated N-doped carbon composites as a highly efficient electrocatalyst for eNO3RR by using monodispersed polystyrene spheres (PS) as sacrificial templates (MR Co-NC). By taking advantage of the large specific area of the pore-rich structures and the high intrinsic activity of metallic Co, the MR Co-NC shows remarkable activity toward eNO3RR, which achieves a partial current density of 268 mA cm−2 with a Faradaic efficiency (FE) of 95.35 ± 1.75 % and a generation rate of 1.25 ± 0.023 mmol h−1 cm−2 for NH3 production under the optimal conditions. The porous carbon skeleton was found to play a dual role by simultaneously protecting the active sites from oxidation and facilitating long-range charge and mass transfer. Theoretical calculations reveal a lower energy barrier of the rate-determining step (*NO2 + H2O + 2e- → *NO + 2OH-) on the metallic Co of MR Co-NC over β-Co(OH)2 formed by the reconstruction of carbon-free Co nanoparticles.