Mesoporous dendritic fibrous nanosilica (DFNS) stimulating mix matrix membranes towards superior CO2 capture

Construction of bismuth oxide iodide (BiOI)/zinc titanium oxide (Zn2TiO4) p-n heterojunction nanofibers with abundant oxygen vacancies for improving photocatalytic carbon dioxide reduction

The conversion of carbon dioxide (CO2) into value-added syngas represents an effective approach for addressing both environmental issues and carbon neutrality issue. However, the slow charge dynamics and low CO2 affinity severely limit the photocatalytic CO2 reduction reaction. In this study, bismuth oxide iodide (BiOI)/zinc titanium oxide (Zn2TiO4) composite nanofibers were successfully prepared by immobilizing BiOI nanosheets on Zn2TiO4 electrospun nanofibers through a solvothermal reaction method. The results of photocatalytic research indicate that the BiOI/Zn2TiO4 composite nanofibers exhibit improved photocatalytic activity in CO2 reduction compared to pristine BiOI nanosheets and Zn2TiO4 nanofibers. The highest carbon monoxide (CO) release rate of BiOI/Zn2TiO4 nanofibers could reach 9.10 µmol‧g-1‧h-1, which is 18.6 times and 6.6 times higher than that of pristine BiOI nanosheets and Zn2TiO4 nanofibers, respectively. The enhanced photocatalytic activity can be credited to the formed BiOI/Zn2TiO4 p-n heterojunction, which can boost electron separation, reduce charge recombination at the interface, and promote the reaction process. The presence of oxygen vacancies in BiOI/Zn2TiO4 nanofibers can not only provide active site to facilitate the adsorption and activation of CO2 molecules, but also adjust the energy band structure of the catalyst to accelerate carriers transfer. After four cycles of testing, the CO release rate of BiOI/Zn2TiO4 nanofibers remains nearly constant, demonstrating its excellent stability. This work develops a feasible strategy to improve the efficiency of photoreduction of CO2 through energy band engineering and surface defect technology.

Revealing the role of hydrogen bond coupling structure for enhanced performance of the solid-state electrolyte

Achieving practical applications of PEO-based composite solid electrolyte (CPE) batteries requires the precise design of filler structures at the molecular level to form stable composite interfacial phases, which in turn improve the conductivity of Li+ and inhibit the nucleation growth of lithium dendrites. Some functional fillers suffer from severe agglomeration due to poor compatibility with the polymer base or grain boundary migration, resulting in limited improvement in cell performance. In this paper, ILs@KAP1 is reported as a filler to enhance the performance of PEO-based batteries. Thereinto, the hypercrosslinked phosphorus ligand polymer-containing KAP1, designed at the molecular level, has an abundant porous structure, hydrogen bonding network, and a rigid skeleton structure of benzene rings. These can be used both to improve the flammability with PEO-based and to reduce the crystallinity of the polymer electrolyte. Ionic liquids (ILs) are encapsulated in the nanochannels of KAP1, and thus a 3D Li+ conducting framework could be formed. In this case, it could not only facilitate the wettability of the contact interface with the electrode, significantly promoting its compatibility and providing a fast Li+ transport path, but also facilitate the formation of LiF, Li3N and Li2O rich SEI components, further fostering the uniform deposition/exfoliation of lithium. The LFP||CPE||Li battery assembled with ILs@KAP1-PEO-CPE has a high initial discharge specific capacity about 156 mAh/g at 1C and a remaining capacity about 121.8 mAh/g after 300 cycles (capacity retention of 78.07%).

Breaking The Permeance-Selectivity Tradeoff for Post-Combustion Carbon Capture: A Bio-Inspired Strategy to Form Ultrathin Hollow Fiber Membranes

Thin film composite (TFC) hollow fiber membranes with ultrathin selective layer are desirable to maximize the gas permeance for practical applications. Herein, a bio-inspired strategy is proposed to fabricate sub-100-nm membranes via a tree-mimicking polymer network with amphipathic components featuring multifunctionalities. The hydrophobic polydimethylsiloxane (PDMS) brushes act as the roots that can strongly cling to the gutter layer, the PDMS crosslinkers function as the xylems to enable fast gas transport, and the hydrophilic ethylene-oxide moieties (brushes and mobile molecules) resemble tree leaves that selectively attract CO2 molecules. As a result, a ≈27 nm-thick selective layer can be attached to the hollow fiber-supported PDMS gutter layer through a simple dip-coating method without any modification. Furthermore, a CO2 permeance of ≈2700 GPU and a CO2 /N2 selectivity of ≈21 that is beyond the permeance-selectivity upper bound for hollow fiber membranes is achieved. This bio-inspired concept can potentially open the possibility of scalable hollow fiber membranes production for commercial applications in post-combustion carbon capture and beyond.

Utilization of a mixed matrix membrane modified by novel dendritic fibrous nanosilica (KCC-1-NH-CS2) toward water purification

Various nanostructures have been used to improve the performance of nanocomposite membranes. Dendritic fibrous nanosilica (DNFS) is a new nanostructure and its performance as an adsorbent for the removal of pigments has been investigated. In this study, a type of modified dendritic fibrous nanosilica containing CS₂ groups (KCC-1-NH-CS₂) was synthesized and inserted as an additive into nanocomposite acrylonitrile–butadiene–styrene (ABS) membranes. Due to its high surface area and unique functional groups, this additive can improve the membrane's ability to remove dyes from aqueous media. Synthesized nanostructures and membranes were characterized by different analysis. The results showed that the water contact angle as a measure of surface hydrophilicity in membrane M₅ compared to membrane M₁ decreased from 79° to 67°. Water absorption (swelling degree) in membrane M₅ increased by more than 100% compared to the bare membrane. Also, this membrane, despite having high porosity (42%) and improved flux (35 L m⁻² h⁻¹), has a better efficiency in removing dyes (MG: 99%, MB: 98%, MO: 82%) in comparison with other reported works.

KCC-1-NH-CS₂ has been used to improve the performance of acrylonitrile–butadiene–styrene membrane.

Porous carbon supported calcium oxide for CO2 adsorption and separation of CO2/CH4

Calcium oxide incorporated porous carbon materials were synthesized by the impregnation method to study CO₂ adsorption and separation of CO₂/CH₄. The X-ray diffraction, Raman analysis, N₂ isotherms at 77 K, and SEM with EDX analysis were used to characterize synthesized materials. XRD and N₂ isotherm results have confirmed that synthesized carbon has porosity, and EDX analysis has reported that the presence of CaO on porous carbon. 10CaO/porous carbon has shown 31 cm³ g^-1 of CO₂ adsorption which was higher than bare porous carbon CO₂ adsorption 17.5 cm³ g^-1 at 298 K, 1 bar. It was attributed to electrostatic interaction between CaO and CO₂. However, CH₄ adsorption was decreased by a decrease in surface area. The selectivity of CO₂/CH₄ was higher for 10CaO/porous carbon and the heat of CO₂ adsorption was 36 KJ/mol at high adsorption of CO₂. Moreover, CO₂ adsorption was the same in each adsorption cycle.

Dendritic Fibrous Colloidal Silica Internally Cross-linked by Bivalent Organic Cations: An Efficient Support for Dye Removal and the Reduction of Nitrobenzene Derivatives

We designed a new unique amphoteric monodisperse colloid with a large complex internal structure, in which silica surfaces are bridged with an organic cross-linker. The rationale was that such colloids would be excellent adsorbents for cationic and anionic dyes and, when doped with noble metal nanoparticles, would be an excellent catalyst for the reduction of a variety of organic compounds. In the first step, the organo-silica bridging agent (bivalent organic cross-linkers) DABCO-S (silanated DABCO) was prepared through a simple nucleophilic substitution reaction between (3-chloropropyl)triethoxysilane and bivalent 1,4-diazabicyclo[2.2.2]octane (DABCO) (a strong base). In the second step, a DABCO-S bridge was introduced into dendritic fibrous nanostructured colloidal silica (DFNS) under open-vessel reflux conditions. We refer to the product obtained by incorporating DABCO-S in DFNS as DDS. The unique characteristics of DFNS are completely preserved in this new type of periodic mesoporous organo-silica-DFNS. The produced nanocomposite has a high surface area of about 807 m² g^-1, a large pore volume of 1.9 cm³ g^-1, and a bimodal pore size distribution, with small 2.5 nm pores and large 30 nm pores. As such, DDS is an efficient adsorbent for dye removal from wastewater. The results show that DDS can adsorb positive and negative dyes such as methylene blue, orange II sodium salt (OR), and procion red mx-58 (PR) with a capacity of 678, 3192, and 3190 mg dye/g adsorbent. Introducing silver nanoparticles in situ into DDS leads to a composite with excellent accessibility of reactants to the Ag surface, resulting in an efficient catalytic reduction of nitro aromatic compounds (NACs) in aqueous media.

Interface-Constrained Layered Double Hydroxides for Stable Uranium Capture in Highly Acidic Industrial Wastewater

Low acid endurance of layered double hydroxides (LDHs) limits their uranium(VI) [U(VI)] adsorption capability from harsh industrial wastewater. Here, we demonstrate magnesium-cobalt LDHs (Mg-Co LDHs) anchored in situ onto the pore channel of dendritic fibrous nanosilica (DFNS) via an interface-constrained strategy. The synergy of Mg-Co LDHs and DFNS not only improves the endurance of the Mg-Co LDH under harsh acidic conditions but also increases the number of active sites of DFNS. Thus, DFNS@Mg-Co LDH shows a high U(VI) uptake capacity (1143 mg g^-1) at pH = 3 and C₀ = 598.7 mg L^-1, which is about 4.8-fold higher than that of pristine DFNS. The DFNS@Mg-Co LDH exhibits excellent U(VI) uptake in various background water circumstances due to its acid endurance and highly selective adsorption. This interface-constrained strategy provides LDH materials with durability under extremely acidic conditions along with a high adsorption capacity, which is promising for uranium capture from various water fields.

Functionalized KIT-6/Polysulfone Mixed Matrix Membranes for Enhanced CO2/CH4 Gas Separation

The development of mixed matrix membranes (MMMs) for effective gas separation has been gaining popularity in recent years. The current study aimed at the fabrication of MMMs incorporated with various loadings (0–4 wt%) of functionalized KIT-6 (NH₂KIT-6) [KIT: Korea Advanced Institute of Science and Technology] for enhanced gas permeation and separation performance. NH₂KIT-6 was characterized by field emission scanning electron microscope (FESEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR), and N₂ adsorption–desorption analysis. The fabricated membranes were subjected to FESEM and FTIR analyses. The effect of NH₂KIT-6 loading on the CO₂ permeability and ideal CO₂/CH₄ selectivity of the fabricated membranes were investigated in gas permeation and separation studies. The successfulness of (3-Aminopropyl) triethoxysilane (APTES) functionalization on KIT-6 was confirmed by FTIR analysis. As observed from FESEM images, MMMs with no voids in the matrix were successfully fabricated at a low NH₂KIT-6 loading of 0 to 2 wt%. The CO₂ permeability and ideal CO₂/CH₄ selectivity increased when NH₂KIT-6 loading was increased from 0 to 2 wt%. However, a further increase in NH₂KIT-6 loading beyond 2 wt% led to a drop in ideal CO₂/CH₄ selectivity. In the current study, a significant increase of about 47% in ideal CO₂/CH₄ selectivity was achieved by incorporating optimum 2 wt% NH₂KIT-6 into the MMMs.

Top-Down Polyelectrolytes for Membrane-Based Post-Combustion CO2 Capture

Polymer-based CO2 selective membranes offer an energy efficient method to separate CO2 from flue gas. `Top-down' polyelectrolytes represent a particularly interesting class of polymer materials based on their vast synthetic flexibility, tuneable interaction with gas molecules, ease of processability into thin films, and commercial availability of precursors. Recent developments in their synthesis and processing are reviewed herein. The four main groups of post-synthetically modified polyelectrolytes discern ionised neutral polymers, cation and anion functionalised polymers, and methacrylate-derived polyelectrolytes. These polyelectrolytes differentiate according to the origin and chemical structure of the precursor polymer. Polyelectrolytes are mostly processed into thin-film composite (TFC) membranes using physical and chemical layer deposition techniques such as solvent-casting, Langmuir-Blodgett, Layer-by-Layer, and chemical grafting. While solvent-casting allows manufacturing commercially competitive TFC membranes, other methods should still mature to become cost-efficient for large-scale application. Many post-synthetically modified polyelectrolytes exhibit outstanding selectivity for CO2 and some overcome the Robeson plot for CO2/N2 separation. However, their CO2 permeance remain low with only grafted and solvent-casted films being able to approach the industrially relevant performance parameters. The development of polyelectrolyte-based membranes for CO2 separation should direct further efforts at promoting the CO2 transport rates while maintaining high selectivities with additional emphasis on environmentally sourced precursor polymers.

Silica-Based RO Membranes for Separation of Acidic Solution

The development of acid separation membranes is important. Silica-based reverse osmosis (RO) membranes for sulfuric acid (H₂SO₄) solution separation were developed by using a counter diffusion chemical vapor deposition (CVD) method. Diphenyldimethoxysilane (DPhDMOS) was used as a silica precursor. The deposited membrane showed the H₂SO₄ rejection of 81% with a total flux of 5.8 kg m⁻² h⁻¹ from the 10⁻³ mol L⁻¹ of H₂SO₄. The γ-alumina substrate was damaged by the permeation of the H₂SO₄ solution. In order to improve acid stability, the silica substrates were developed. The acid stability was checked by the gas permeation tests after immersing in 1 mol L⁻¹ of the H₂SO₄ solution for 24 h. The N₂ permeance decreased by 11% with the acid treatment through the silica substrate, while the permeance decreased to 94% through the γ-alumina substrate. The flux and the rejection through the DPhDMOS-derived membrane on the silica substrate were stable in the 70 wt % H₂SO₄ solution.

Improving the size uniformity of dendritic fibrous nano-silica by a facile one-pot rotating hydrothermal approach

This article provides a facile, low-cost, and reproducible one-pot rotating hydrothermal approach to synthesize dendritic fibrous nano-silica with outstanding uniformity.

Dendritic fibrous nano-silica & titania (DFNST) spheres as novel cataluminescence sensing materials for the detection of diethyl ether

Selective and controllable cataluminescence (CTL) sensors for volatile organic compounds (VOCs) are significant for chemical safety, environmental monitoring, health effects on human beings, and so forth. Most of the exploited CTL-based sensors suffer relatively low response and poor selectivity because of their high sensitivities to interferential substances. In this investigation, dendritic fibrous nano-silica & titania (DFNST) spheres have been synthesized as novel sensing materials and the corresponding DFNST-based CTL sensor has been fabricated to detect diethyl ether with high selectivity via a method of utilizing one 440 nm bandpass filter. The as-prepared DFNST hybrids not only keep the excellent dendritic fibrous morphology but also bear ca. 21 wt% catalytic titanium oxide of anatase crystalline structure. The DFNST-based sensor exhibits extremely strong CTL emission at 440 nm toward diethyl ether against other VOCs like acetone, ethyl acetate, butanol, and so forth. The high response can be attributed to the unique architectural texture of DFNST. Under the optimum parameters, ether could be easily detected in a wide range from 2.0 to 40.0 mM with a fine detection limit of 1.55 mM (S/N = 3). Furthermore, the working life of this CTL sensor is satisfactory with outstanding stability and durability, far from damaging the morphology and activity of the DFNST sensing material. In conclusion, it is expected that this novel sensing material, the relevant CTL sensor, and the approach of employing the bandpass filter will be significant for the detection of diethyl ether in actual applications.

Dendritic fibrous nano-silica & titania (DFNST) nanospheres have been successfully prepared as the sensing materials for the detection of diethyl ether via a DFNST-based cataluminescence (CTL) sensor.