Hierarchical Porous Membrane Research Articles

Self-supporting and hierarchical porous membrane of bacterial nanocellulose@metal-organic framework for ultra-high adsorption of Congo red

The widespread use of synthetic dyes has serious implications for both the environment and human health. Therefore, there is an urgent need for the development of novel, high-efficiency adsorbents for these dyes. In this study, a Zirconium-based metal-organic framework (MOF) with controllable morphology was in-situ grown on bacterial nanocellulose (BC) via a solvothermal method. The resulting BC@MOF composite nanofibers have a high specific surface area of 651 m2/g and can be assembled into a self-supported porous membrane (BMMCa) through vacuum filtration with the assistance of calcium ions. The addition of Ca(II) significantly enhanced the mechanical properties of the membrane through dispersion effect and electrostatic interactions, as well as enhancing its adsorption performance through the salting-out effect. The BMMCa membrane, with its hierarchical porous structure and high flux, exhibits high selectivity for Congo red (CR) with an ultra-high adsorption capacity of 3518.6 mg/g. Furthermore, the self-supporting membrane achieved rapid and convenient removal of CR through circulating filtration adsorption. The adsorption mechanism and selectivity were verified through the molecular dynamics simulation calculations by Materials Studio (MS) software. This membrane-based adsorbent, with its ultra-high adsorption capacity, good selectivity, and recycling ability, has great potential for practical wastewater treatment applications.

Novel robust hierarchical porous membrane for uranium enrichment: fabrication, degradation behavior, and uranium sorption performance

Fabrication of hierarchical porous CAP membrane for uranium sorption.

Unprecedented water permeation in nanostructured PVDF membranes prepared by unidirectional freezing and surface melting method

Phase inversion has played a vital role in membrane technology by offering the economic viability for producing polymeric membrane in quantity, and it allows for the development of wastewater treatment technologies with the membrane as a promising energy-saving separator. However, most existing phase inversion membranes suffer from low permeance, thus diminishing their advantages in the quest for more efficient and sustainable separation processes. Here, based on unidirectional freezing approach, we showcase a hierarchical porous membrane that outperforms the permeance of the phase inversion membranes without compromising the membranes’ separation capabilities. An unprecedented surface melting atop a frozen membrane cast film promotes the phase inversion in the water phase, which in turn constructs an additional separating layer on membrane surface. These membranes exhibit tuneable pores in the range between 9 and 50 nm and pure water permeation which is 16–25 times higher than that of an equivalent industry standard. Moreover, the synergy between freezing and melting enables a separate design of pore sizes from membrane both surfaces, leading to a dual-skin polymeric membrane showing enhanced functionality throughout its cross-section. With the enhanced efficiencies, these membranes have potential to positively contribute to the current water-energy nexus, by considerably improving the economic and technological viability of many water-treatment and filtration-based separation systems.

A hierarchical porous membrane achieved by femtosecond laser scribing with water-repellent, highly breathable and photo-thermal ability

The multifunctional membranes play an important role in our daily life as well as in scientific research such as the protective clothing and membrane distillation. Here, a kind of water-repellent, highly breathable and photo-thermal multifunctional membrane was fabricated by femtosecond laser one-step direct writing. The as-prepared membrane exhibited strong repulsive and low adhesion to various liquids (water, tea, milk, coffee and glycerin). Moreover, the membrane also shown good stability in the related tests of surface wettability. In addition, it provided good permeability to both water vapor and ordinary air based on its porous structures. In the comparative test of the photothermal properties with the pristine polytetrafluoroethylene (PTFE) membrane, it also showed excellent performance of higher absorption rate and rapid temperature rise.

Attapulgite and multiwalled carbon nanotubes co-integrated hierarchical porous polyacrylonitrile membrane as a multifunctional interlayer for lithium-sulfur batteries with enhanced performance

• ATTP and MWCNTs co-integrated porous PAN membrane was first fabricated. • The membrane was investigated as a multifunctional interlayer for Li-S batteries. • A synergistic effect of ATTP and MWCNTs effectively suppress the shuttle effect. • The cell with such interlayer demonstrates superior cycling stability . As a kind of natural porous nanorods, attapulgites (ATTP) are widely used in many fields because of their high specific surface area, high porosity and strong adsorption ability. In this work, ATTP and multiwalled carbon nanotubes (MWCNTs) co-integrated polyacrylonitrile (PAN) hierarchical porous membrane (ATTP/CNTs@PAN) has been fabricated and investigated as a multifunctional interlayer for lithium-sulfur batteries. Due to a synergistic effect of ATTP and the carboxylated MWCNTs, the porous interlayer is able to effectively suppress the shuttle effect by trapping and confining the dissolved polysulfides. Meanwhile, the addition of MWCNTs improves the conductivity of the composite membrane, which is beneficial for the reutilization of the active species. Therefore, the cells with the interlayer demonstrates superior electrochemical performance, delivering a high initial discharge capacity of 1283 mAh g −1 at 0.2 C, and retaining 785 mAh g −1 after 300 cycles with a Coulombic efficiency exceeding 99%. Meaningfully, this porous composite membrane is low-cost and very effective for high performance Li-S batteries.

Highly Efficient Polysulfide Trapping and Ion Transferring within a Hierarchical Porous Membrane Interlayer for High-Energy Lithium–Sulfur Batteries

Inserting an interlayer between the sulfur cathode and the separator has been considered as one of the most promising solutions to suppress the shuttle effect of soluble lithium polysulfide interme...

Manganese dioxide-filled hierarchical porous nanofiber membrane for indoor air cleaning at room temperature

Indoor air pollution, including atmospheric particular matter 2.5 (PM2.5) and chemical gaseous pollutants (HCHO), has been an ongoing concern. Seeking a practical strategy for protection of the indoor air quality (IAQ) remains a challenge. Herein, we demonstrated a hierarchical porous membrane consisting of the birnessite-type MnO2 that was filled in the polystyrene porous nanofibers (MnO2/PS HPNM) fabricated by a versatile electrospinning method. The effective air cleaning of both PM2.5 and HCHO at remarkably low resistance was achieved by dominating the hierarchical porous structure. The HCHO gas could easily permeate through the mesopores of the PS nanofibers and contact MnO2, thereby resulting in an excellent HCHO removal efficiency of 88.2% after the initial run and 74% after five cycles. In addition, the pore-filling MnO2 with the layered structure increased the nanofiber membrane surface area, thus enhancing its PM capture performance (99.77%). Moreover, the macropores from the interwoven nanofibers ensured clean air penetration leading to a low airflow resistance of 82 Pa. The hierarchical multifunction porous structure membrane provided a new approach for the IAQ protection.

Maskless microfabrication of nanowire-decorated porous membrane for rapid purification of contaminated water

Due to widespread droughts and population increase, the rapid and sustainable purification of contaminated water is of major interest to human beings. Toward this end, this paper reports a handheld and efficient purification system using maskless micro/nanofabrication techniques. A porous polymer membrane decorated with nanomaterials was tailored to physically filter pollutants in contaminated water. To create the porous polymer membrane, curable polymer and black sugar powder were used for a facile and cost-effective fabrication method. The black sugar particles linked in cured polymer were selectively dissolved in hot water, forming micro-sized pores for filtering out pollutants. The nanowires were hydrothermally grown onto the porous membrane to further improve the purification performance by capturing finer pollutants between nanowires. The combination of nanowires and 50-wt% concentration of black sugar particle, forming a porosity of ~ 27.71% showed the minimum residual rate (i.e., weight of pollutants in purified water) of 0.981 mg/ml. This study supports the use of hierarchical porous membrane for the efficient and sustainable purification of contaminated water within a short period time.

Thermoresponsive Stiffness Softening of Hierarchically Porous Nanohybrid Membranes Promotes Niches for Mesenchymal Stem Cell Differentiation.

Despite the attention given to the development of novel responsive implants for regenerative medicine applications, the lack of integration with the surrounding tissues and the mismatch with the dynamic mechanobiological nature of native soft tissues remain in the current products. Hierarchical porous membranes based on a poly (urea-urethane) (PUU) nanohybrid have been fabricated by thermally induced phase separation (TIPS) of the polymer solution at different temperatures. Thermoresponsive stiffness softening of the membranes through phase transition from the semicrystalline phase to rubber phase and reverse self-assembly of the quasi-random nanophase structure is characterized at body temperature near the melting point of the crystalline domains of soft segments. The effects of the porous structure and stiffness softening on proliferation and differentiation of human bone-marrow mesenchymal stem cells (hBM-MSCs) are investigated. The results of immunohistochemistry, histological, ELISA, and qPCR demonstrate that hBM-MSCs maintain their lineage commitment during stiffness relaxation; chondrogenic differentiation is favored on the soft and porous scaffold, while osteogenic differentiation is more prominent on the initial stiff one. Stiffness relaxation stimulates more osteogenic activity than chondrogenesis, the latter being more influenced by the synergetic coupling effect of softness and porosity.

Fabrication of hierarchical porous N-doping carbon membrane by using “confined nanospace deposition” method for supercapacitor

The membrane carbon materials with hierarchical porous architecture are attractive because they can provide more channels for ion transport and shorten the ions transport path. Herein, we develop a facile way based on “confined nanospace deposition” to fabricate N-dopi-ng three dimensional hierarchical porous membrane carbon material (N-THPMC) via coating the nickel nitrate, silicate oligomers and triblock copolymer P123 on the branches of commercial polyamide membrane (PAM). During high temperature treatment, the mesoporous silica layer and Ni species serve as a “confined nanospace” and catalyst respectively, which are indispensable elements for formation of carbon framework, and the gas-phase carbon precursors which derive from the decomposition of PAM are deposited into the “confined nanospace” forming carbon framework. The N-THPMC with hierarchical macro/meso/microporous structure, N-doping (2.9%) and large specific surface area (994m2 g-1) well inherits the membrane morphology and hierarchical porous structure of PAM. The N-THPMC as electrode without binder exhibits a specific capacitance of 252 F g-1 at the current density of 1 A g-1 in 6 M KOH electrolyte and excellent cycling stability of 92.7% even after 5000 cycles.

Hierarchical porous poly (ether sulfone) membranes with excellent capacity retention for vanadium flow battery application

Abstract A hierarchical poly (ether sulfone) (PES) porous membrane is facilely fabricated via a hard template method for vanadium flow battery (VFB) application. The construction of this hierarchical porous membrane is prepared via removing templates (phenolphthalein). The pore size can be well controlled by optimizing the template content in the cast solution, ensuring the membrane conductivity and selectively. The prepared hierarchical porous membrane can combine high ion selectivity with high proton conductivity, which renders a good electrochemical performance in a VFB. The optimized hierarchical porous membrane shows a columbic efficiency of 94.52% and energy efficiency of 81.66% along with a superior ability to maintain stable capacity over extended cycling at a current density of 80 mA cm−2. The characteristics of low cost, proven chemical stability and high electrochemical performance afford the hierarchical PES porous membrane great prospect in VFB application.

Tailoring the hierarchical porous structure within polyethersulfone/cellulose nanosheets mixed matrix membrane to achieve efficient dye/salt mixture fractionation

Mixed matrix concept using cellulose nanosheets (CNs) and polyethersulfone was employed to fabricate hierarchical porous membrane with potential application for efficient dye/salt mixture fractionation. To this end, CNs was extracted by acid hydrolysis of alpha cellulose and incorporated in polyethersulfone casting solutions at four concentration levels. After that, membranes were manufactured by typical nonsolvent induced phase separation method. Effect of CNs incorporation on thermodynamic stability and phase separation behavior of polymer solution was investigated by construction of phase diagram. In addition, the obtained flat-sheet membranes characteristics including surface morphology, cross-section structure, thermal decomposition, porosity, pore size and pure water flux, were investigated. CNs filled membranes were also evaluated for fractionation of direct dye/NaCl binary mixture. Results reveal that, two stages of phase separation process are observed in CNs filled solution, in which the early stage can initiate with lower water content. This leads to fabrication of more porous membranes with longer finger-like cavities which were confirmed by FESEM analysis of the membranes. Results of TGA reveal that, two weight loss steps forms during decomposition process of CNs filled membranes. It was also observed that addition of 1.5 wt.% CNs into polymer solution increases water permeability from 20 to 90 L/m2 h. Application of 1.5 wt.% CNs filled membranes for fractionation of binary mixture containing direct red 23 (1 g/l) and NaCl (40 g/l) revealed that dye rejection and salt penetration percentages of obtained membranes are 98 % and 97 % respectively. Results confirm the potential of CNs filled membrane as a novel and promising approach for highly efficient fractionation of salt/dye mixtures, owning to its fabrication simplicity and perfect structural features.