Selective Adsorption Capability Research Articles

Innovative eco-friendly methyl orange removal: Mechanism, kinetic, and thermodynamic study using starch cryogel-integrated mesoporous silica nanoparticles

This study introduces a novel, eco−friendly composite, uncalcined mesoporous silica nanoparticles incorporated into a starch cryogel (MSNs-Cry), designed for the effective removal of methyl orange (MO) from water. MSNs−Cry integrates uncalcined mesoporous silica nanoparticles (MSNs) within a starch cryogel network, leveraging the high adsorption capacity of MSNs. The composite achieved a maximum adsorption capacity of 18.98 mg g⁻1 and demonstrated high removal efficiencies of 99.00 % ± 0.21 % in synthetic water (10 mg L−1 MO) and 92.77 % ± 1.76 % in real wastewater containing 0.43 mg L−1 MO. The Langmuir isotherm model provided a superior fit (R2 = 0.9930) compared to the Freundlich model (R2 = 0.9180), and the adsorption kinetics followed a pseudo−second−order model (R2 = 0.9917). The primary adsorption mechanisms included electrostatic attraction, hydrophobic interactions, and hydrogen bonding. The process was endothermic (ΔH° = 31.3 kJ mol−1), spontaneous, and more favorable at higher temperatures (ΔG° = −34.2 to −38.6 kJ mol−1 at 298–318 K). In the presence of sodium silicate at 13.1 times the MO concentration, removal efficiency drops by 35.77 %, and with sodium sulfate and urea at 100 times the MO concentration, it decreases by 8.65 %. Despite these challenges, MSNs−Cry effectively removes MO in the presence of the anionic dye Congo Red and metal ions, demonstrating its selective adsorption capabilities. The tablet form of MSNs−Cry prevents the loss of uncalcined MSNs, mitigating potential environmental and operational impacts. Additionally, the composite's effectiveness at a natural pH of 6.65 eliminates the need for pH adjustment, offering a cost−effective solution for real−world applications. This study establishes MSNs−Cry as a promising material for sustainable water purification.

Improving gas separation performance by boron nitride nanotubes

The performance of boron nitride nanotubes (BNNTs) and carbon nanotubes (CNTs) in multiple gas separation systems was systematically compared using molecular simulation methods. Findings reveal that under conditions of 298 K and 2 MPa, BNNTs generally show higher adsorption selectivities than CNTs for CH4/N2, CO2/CH4, and CO2/N2 mixtures. Notably, in the CO2/CH4 system, BNNTs exhibit a selectivity of up to 350 at a radius of 0.48 nm, significantly surpassing the 14 observed for CNTs; in the CO2/N2 system, selectivity can reach as high as 969 for BNNTs, contrasting with the 69 for CNTs. Furthermore, BNNTs achieve saturation adsorption for CF4 at 0.04 MPa with a capacity of 2.7 mmol/g, while CNTs show a higher adsorption capacity for N2, reflecting the superior selective adsorption capability of BNNTs for specific gases. Analysis of nanotubes with different chiral configurations led to the recommendation of (11,11) and (7,7) chiralities as optimal structures for efficient gas separation. Fluctuations in energy contributions from fluid-wall interactions in BNNTs, are closely related to their selectivity fluctuations. The results demonstrate that BNNTs, due to their unique structural characteristics, possess significant potential in the field of gas adsorption and separation, particularly in enhancing the selective adsorption of CO2 and CF4.

Synthesis of Carboxyl-Functionalized COFs with Alternate Stable β-Ketoenamine and Benzimidazole Linkages: Unraveling Exceptional Solvent Effects for Efficient Uranium Separation.

The prevalent π-π interactions in 2D covalent organic frameworks (COFs) impart a certain flexibility to the structures, making the stacking of COF layers susceptible to external stimuli and introducing some structural disorder. Recent research indicates that the flexibility between COF layers and the associated disorder significantly influence their selective adsorption performance toward gas molecules. However, the adsorption process in a solution environment is more complex compared to gas-phase adsorption, involving interactions between adsorbents and adsorbates, as well as the solvation effects of flexible 2D COFs. Therefore, the inherent flexibility and disorder in 2D COFs under solution conditions and their impact on the adsorption performance of metal ions have not been observed yet. Herein, the synthesis of a novel carboxyl-functionalized COF featuring stable β-ketoenamine and benzimidazole linkages, named DMTP-COOH, is presented. DMTP-COOH exhibits excellent selective adsorption capability for uranium, with significantly different adsorption capacities observed after treatment with different solvents. This notable difference in adsorption capacity is observed under varying pH, concentration, time, and even in the presence of multiple competing ions. This work represents the first observation of the significant impact of solvent soaking treatment on the selective adsorption performance of COFs for uranium under liquid conditions.

Selective adsorption of coalbed methane on multilayer defective graphene nanostructures and their Mn-modified nanostructures: A DFT study

Coalbed methane (CBM) is an unconventional natural gas with CH4 as the main component. It is found in coal seams and surrounding rocks. The development and exploitation of CBM is a promising approach to ensure the safety of coal mine production, reduce greenhouse effects, and increase clean energy resources. Based on the first-principles calculations in conjunction with a grand canonical Monte Carlo (GCMC) simulation, this paper aims to examine the effects of interlayer spacing and Mn modification on CBM and CO2 adsorption. We assess the CH4 storage performance in multilayered defective graphene nanostructures (MDGNs). Using density functional theory in conjunction with the Grimm correction method (DFT-D approach), both the adsorption energy and charge distribution between CBM components and extended line defects (ELD) are appropriately evaluated in the presence or lack of Mn modification (Mn-ELD). The GCMC simulation is implemented to investigate CH4 adsorption isotherms of MDGN and Mn-MDGN configurations at 298.15 K. The selective adsorption capabilities of MDGNs and Mn-MDGNs for CO2, N2, and CH4 are also systematically analyzed. The obtained results reveal that an Mn-MDGN configuration with an interlayer spacing of dGL=1.02 nm is effective in sequestering CO2 from CBM. In contrast, MDGN configurations with interlayer spacings of dGL=0.68 and 1.02 nm are more effective for the storage of purified CBM. In continuing, the CH4 purification mechanism in Mn-MDGNs and the CH4 storage mechanism in MDGNs are also methodically explored at the molecular level. The research work reported here can serve as a crucial guide for the future development and utilization of CBM.

Facile Fabrication of Porous Adsorbent with Multiple Amine Groups for Efficient and Selective Removal of Amaranth and Tartrazine Dyes from Water.

The development of an advanced dye adsorbent that possesses a range of beneficial characteristics, such as high adsorption capacity, swift adsorption kinetics, selective adsorption capability, and robust reusability, remains a challenge. This study introduces a facile method for fabricating an amine-rich porous adsorbent (ARPA), which is specifically engineered for the adsorptive removal of anionic dyes from aqueous solutions. Through a comprehensive assessment, we have evaluated the adsorption performance of ARPA using two benchmark dyes: amaranth (ART) and tartrazine (TTZ). Our findings indicate that the adsorption process reaches equilibrium in a remarkably short timeframe of just 20 min, and it exhibits an excellent correlation with both the Langmuir isotherm model and the pseudo-second-order kinetic model. Furthermore, ARPA has demonstrated an exceptional maximum adsorption capacity, with values of 675.68 mg g-1 for ART and 534.76 mg g-1 for TTZ. In addition to its high adsorption capacity, ARPA has also shown remarkable selectivity, as evidenced by its ability to selectively adsorb TTZ from a mixed dye solution, a feature that is highly desirable for practical applications. Beyond its impressive adsorption capabilities, ARPA can be efficiently regenerated and recycled. It maintains a high level of original removal efficiency for both ART (76.8%) and TTZ (78.9%) even after five consecutive cycles of adsorption and desorption. Considering the simplicity of its synthesis and its outstanding adsorption performance, ARPA emerges as a highly promising material for use in dye removal applications. Consequently, this paper presents a straightforward and feasible method for the production of an effective dye adsorbent for environmental remediation.

A green synthesis method of a mussel-inspired polyphenol-functionalized silica-based material and its highly efficient adsorption of gallium

Three-dimensional mesoporous silica is a distinctive nanomaterial celebrated for its unique structure, substantial specific surface area, enhanced utilization of active surfaces, and improved adsorption and catalytic reaction capabilities. Nevertheless, its limited surface functional groups often impede its effective ion adsorption capacity. Here, inspired by the mussel-adhesive phenomenon, in this study, we introduced a straightforward layer-by-layer assembly approach to fabricate a new series of KIT-6@x-catechol/polyethyleneimine composites, the catechol/polyethyleneimine is the shell and KIT-6 is the core. Importantly, catechol(CA) and polyethyleneimine(PEI) polymers as selective layers with dense structures and abundant cation exchange groups, resulting in outstanding adsorption performance for our material. At a pH of 3.0, Ga(III) exhibited a maximum adsorption capacity of 88.65 mg g−1 on the adsorbent. Furthermore, the adsorbent demonstrated selective adsorption capabilities for Ga(III) over Ge(IV), Al(III), Cu(II), Zn(II), and Co(II). The primary adsorption mechanism of KIT-6@x-CA/PEI is chelation that occurs through coordination between the O atom on the phenolic hydroxyl group of CA and Ga3+, Ga(OH)2+, Ga(OH)2+ under pH 3.0 conditions. In summary, the synthesized KIT-6@x-CA/PEI exhibits significant potential for water treatment containing Ga(III) through adsorption processes.

Selective Adsorption of Cationic and Anionic Dyes using Ni/Al Layered DoubleHydroxide Modified withEucheuma cottonii

This study investigates the selective adsorption capabilities of Ni/Al Layered Double Hydroxide (LDH) modified withEucheumacottoniifor the removal of cationic and anionic dyes from aqueous solutions. The primary objective was to evaluate the efficiencyand selectivity of these modified adsorbents towards different dyes, including rhodamine-b, malachite green, methylene blue(cationic dyes), and direct yellow, methyl orange, direct green (anionic dyes). The modification process aimed to enhancethe adsorption properties of LDHs, leveraging the natural adsorption capabilities ofEucheuma cottonii. Experimental resultsdemonstrated significant differences in adsorption percentages among the tested dyes, with malachite green showing thehighest adsorption efficiency among cationic dyes, indicating a strong affinity of the modified adsorbents towards cationic dyes.However, the ability to also adsorb anionic dyes suggests the dual-functionality of the modified LDHs, making them versatileagents for dye removal in water treatment applications.

Facile synthesis of heteroporous covalent organic frameworks with dual linkages: a “three-in-one” strategy

Covalent organic frameworks (COFs) with dual linkages can combine advantages and properties of two distinct connectors, enabling the development of multifunctional materials. However, due to challenges in simultaneously forming two types of linkages, the synthesis of COFs with dual linkages remains a significant challenge. Herein, we propose a “three-in-one” molecular design strategy for synthesizing COFs with dual linkages (4-amino-4"-(2,2-dioxan-1,3-dioxan-5-yl)-[1,1':3',1"-terphenyl]-5'-yl) boronic acid (ADTB)-COF and (4'-amino-5'-(4-(2,2-dioxan-1,3-dioxan-5-yl)phenyl)-[1,1':3',1'-teroxan]-5-yl) boronic acid (ADPB)-COF through reversible condensation between three distinct functionalization groups on the monomer. Benefitting from the abundant micropores and high surface area, ADPB-COF showed excellent selective adsorption capability of C3H8 over CH4 (174, 298 K/1 bar). The present work introduces a new approach for constructing COFs with dual linkages, which greatly simplifies the synthesis process and provides a novel opportunity to develop functional materials based on COFs with multi-linkages.

Harnessing the power of polyethyleneimine in modifying chitosan surfaces for efficient anion dyes and hexavalent chromium removal

In this investigation, synthesis of a surface-functionalized chitosan known as amino-rich chitosan (ARCH) was achieved by successful modification of chitosan by polyethyleneimine (PEI). The synthesized ARCH was characterized by a specific surface area of 8.35 m2 g−1 and a microporous structure, with pore sizes predominantly under 25 nm. The Zeta potential of ARCH maintained a strong positive charge across a wide pH range of 3–11. These characteristics contribute to its high adsorption efficiency in aqueous solutions, demonstrated by its application in removing various anionic dyes, including erioglaucine disodium salt (EDS), methyl orange (MO), amaranth (ART), tartrazine (TTZ), and hexavalent chromium ions (Cr(VI)). The adsorption capacities (Qe) for these contaminants were measured at 1301.15 mg g−1 for EDS, 1025.45 mg g−1 for MO, 940.72 mg g−1 for ART, 732.96 mg g−1 for TTZ, and 350.15 mg g−1 for Cr(VI). A significant observation was the rapid attainment of adsorption equilibrium, occurring within 10 min for ARCH. The adsorption behavior was well-described by the Pseudo-second-order and Langmuir models. Thermodynamic studies indicated that the adsorption process is spontaneous and endothermic in nature. Additionally, an increase in temperature was found to enhance the adsorption capacity of ARCH. The material demonstrated robust stability and selective adsorption capabilities in varied conditions, including different organic compounds, pH environments, sodium salt presence, and in the face of interfering ions. After five cycles of adsorption, ARCH maintained about 60% of its initial adsorption capacity. Due to its efficient adsorption performance, simple synthesis process, low biological toxicity, and cost-effectiveness, ARCH is a promising candidate for future water treatment technologies.

Selectivity descriptors of the catalytic n-hexane cracking process over 10-membered ring zeolites.

Zeolite-mediated catalytic cracking of alkanes is pivotal in the petrochemical and refining industry, breaking down heavier hydrocarbon feedstocks into fuels and chemicals. Its relevance also extends to emerging technologies such as biomass and plastic valorization. Zeolite catalysts, with shape selectivity and selective adsorption capabilities, enhance efficiency and sustainability due to their well-defined network of pores, dimensionality, cages/cavities, and channels. This study focuses on the alkane cracking over 10-membered ring (10-MR) zeolites under industrially relevant conditions. Through a series of characterizations, including operando UV-vis spectroscopy and solid-state NMR spectroscopy, we intend to address mechanistic debates about the alkane cracking mechanism, aiming to understand the dependence of product selectivity on zeolite topologies. The findings highlight topology-dependent mechanisms, particularly the role of intersectional void spaces in zeolite ZSM-5, influencing aromatic-based product selectivity. This work provides a unique understanding of zeolite-catalyzed hydrocarbon conversion, linking alkane activation steps to the traditional hydrocarbon pool mechanism, contributing to the fundamental knowledge of this crucial industrial process.

Facile preparation of tetraphenylethylene-based porous polymer with dual role of adsorption and detection for trinitrotoluene

A novel porous polymer, denoted as tetraphenylethene-based porous polymer (PTPEK), was synthesized via a catalyst-free C–O coupling reaction. The unique combination of dipole-π interactions and π-π interactions within PTPEK facilitated exceptional adsorption property towards trinitrotoluene (TNT). Furthermore, the incorporation of tetraphenylethene groups, which exhibit aggregation-induced emission (AIE) activity, endowed PTPEK with remarkable TNT detection capability. Simultaneously, PTPEK showed excellent selective adsorption capability and outstanding selective fluorescence detection performance for TNT. At room temperature (298 K), PTPEK demonstrated a maximum TNT adsorption capacity of 209.2 mg g−1, reaching 65 % of its adsorption equilibrium within just 1 h. Additionally, PTPEK exhibited a rapid quenching time of 125 s for TNT, with a low detection limit of 4.56 × 10−6 mol/L. Notably, PTPEK also displayed excellent recyclability characteristics.

Design of self-healable and recyclable multi-network hydrogels for efficient and selective removal of cationic dyes

In this study, a novel multi-network hydrogel with self-healing ability was developed with the aim of addressing the limitations of traditional hydrogels in adsorption processes for organic contaminant removal from water. The hydrogel was designed by incorporating poly(acrylic acid) (PAAc) and poly(vinyl alcohol) (PVA) to create both chemical and physical crosslinked networks, while a dynamic ionically crosslinked network was introduced using Fe3+. A comprehensive range of characterization techniques confirmed the successful formation of the multi-network hydrogel. Compared to hydrogels with fewer networks, the newly developed PAAc/PVA@Fe3+ hydrogel exhibited significant enhancements in various key aspects. Notably, it demonstrated improved swelling kinetics, mechanical properties including compression strength, Young's modulus, and stretchability, and a remarkable self-healing ability with an efficiency of 88 % at 25 °C after an 8 h contact period. In batch experiments, the PAAc/PVA@Fe3+ hydrogel displayed selective adsorption capabilities, particularly for cationic dyes like methylene blue (MB), even in binary dye systems. Moreover, the hydrogel showcased impressive recycling and reusability, maintaining an MB removal efficiency of over 60 % even after undergoing 10 reuse cycles. An essential aspect of its performance was the preservation of its adsorption efficiency even after consecutive self-healing processes. The unique combination of selective adsorption, self-healing ability, and robust recycling performance positions this hydrogel as a promising candidate for efficient and sustainable water treatment solutions.

Polymeric Materials for Rare Earth Elements Recovery.

Rare earth elements (REEs) play indispensable roles in various advanced technologies, from electronics to renewable energy. However, the heavy global REEs supply and the environmental impact of traditional mining practices have spurred the search for sustainable REEs recovery methods. Polymeric materials have emerged as promising candidates due to their selective adsorption capabilities, versatility, scalability, and regenerability. This paper provides an extensive overview of polymeric materials for REEs recovery, including polymeric resins, polymer membranes, cross-linked polymer networks, and nanocomposite polymers. Each category is examined for its advantages, challenges, and notable developments. Furthermore, we highlight the potential of polymeric materials to contribute to eco-friendly and efficient REEs recovery, while acknowledging the need to address challenges such as selectivity, stability, and scalability. The research in this field actively seeks innovative solutions to reduce reliance on hazardous chemicals and minimize waste generation. As the demand for REEs continues to rise, the development of sustainable REEs recovery technologies remains a critical area of investigation, with the collaboration between researchers and industry experts driving progress in this evolving field.

Preparation of graphene oxide enhanced magnetic composite hydrogels by one‐pot method for selective adsorption

AbstractMagnetic composite hydrogels exhibit promising prospects for diverse applications, but their mechanical properties impose limitations on their further advancement. In this study, a novel approach is proposed to directly prepare magnetic composite hydrogels utilizing nanoferroferric oxide, aiming to replace the existing preparation method. Meanwhile, graphene oxide (GO) is introduced into magnetic composite hydrogels to enhance their mechanical characteristics. By employing ammonium citrate (AC) as a dispersant, the dispersion of ferroferric oxide magnetic nanoparticles at a concentration of 40 mg/mL is achieved, enabling their coexistence with GO for the preparation of magnetic composite hydrogels. Notably, the incorporation of 3 mg/mL GO and 40 mg/mL magnetic nanoparticles in polyacrylamide (PAM) hydrogel yields remarkable improvements in maximum stress and strain, reaching 148 kPa and 496%, respectively. In contrast, magnetic composite hydrogels without GO exhibit lower values of 46.5 kPa and 351%. The presence of magnetic nanoparticles imparts magnetism to the hydrogel, with higher concentrations of magnetic nanoparticles leading to increased magnetism. Moreover, the presence of AC and GO renders the hydrogels electronegative, thereby endowing them with selective adsorption capabilities. In summary, the magnetic composite hydrogels prepared by one‐pot method have good mechanical properties and selective adsorption capacity, and have good application potential.

Screening of MnO2 with desired facet and its behavior in highly selective adsorption of aqueous Pb (II): Theoretical and experimental studies

In this study, Density Functional Theory (DFT) calculations and experimental methods were adopted to evaluate MnO2 with 5 different facets for their selective adsorption of Pb (II) from wastewater containing Cd (II), Cu (II), Pb (II), and Zn (II). The DFT calculations were performed to screen the selective adsorption capability of the facets and demonstrated that the MnO2 (3 1 0) facet has an excellent performance in selective adsorption of Pb (II) among all facets. The validity of DFT calculations was verified by comparing with the experimental results. MnO2 with different facets was prepared in a controlled manner and the characterizations confirmed that the lattice indices of the fabricated MnO2 have the desired facets. Adsorption performance experiments illustrated a high adsorption capacity (320.0 mg/g) on the (3 1 0) facet MnO2. The selectivity of adsorption of Pb (II) was 3–32 times greater than that of the other coexisting ions, i.e., Cd (II), Cu (II), and Zn (II)), which is consistent with results of the DFT calculations. Furthermore, results of DFT calculations on adsorption energy, charge density difference, and projected density of states (PDOS) showed that the adsorption of Pb (II) on the MnO2 (3 1 0) facet is non-activated chemisorption. This study shows that it is feasible to use DFT calculations to quickly screen suitable adsorbents for environmental applications.

Granular nitrogen-doped carbons with ultra-high C2H2/CO2 adsorption selectivity for C2H2 purification

Purification of C2H2 from C2H2/CO2 mixtures such as cracked gas through the adsorptive separation technology based on porous adsorbent with highly selective adsorption capability is considered as the promising and energy-efficient process in petroleum industry. Herein, granular nitrogen-doped carbons derived from coconut shell were obtained through the urea modification with steam assisted hydrothermal method followed by calcination. They were characterized and their adsorption and separation properties for C2H2/CO2 mixture were systematically investigated. It was found that they macroscopically present the uniform particle sizes (median diameter D50 at around 700 μm), and structurally have the characteristics of developed porosities (Brunauer-Emmett-Teller surface areas up to 430.2 m2/g) and abundant nitrogen-containing functional groups. In particular, their adsorption selectivities for C2H2/CO2 were significantly improved to 7.5 at 25 °C and 1.0 bar, outperforming the granular carbons without nitrogen doping (4.0) and some benchmark powdery adsorbents. Breakthrough experiments indicate that the granular nitrogen-doped carbons can be directly packed in a fixed bed to separate C2H2/CO2 mixture completely under dry conditions (relative humidity = 0 %) and humid conditions (relative humidity = 75.1 %) at 25 °C, and their dynamic separation performance could be well remained during the cyclic experiments. Molecule simulation results further reveal that the pyridinic-N with great binding energy (BE) interactes with C2H2 (-16.27 kJ/mol), and great absolute difference of binding energies (ΔBE) between C2H2 and CO2 (ΔBE pyridinic-N = 5.04 kJ/mol) plays the significant role in improving the C2H2/CO2 adsorption and separation performance of granular nitrogen-doped carbons. Therefore, the granular nitrogen-doped carbons are very promising for purification of C2H2 from C2H2/CO2 mixtures.

Cellulose-incorporated imprinted materials with amphiphilic crosslinking structure for selective adsorption of bisphenol A

The development of cost-effective and easy-operate adsorbents with tunable adsorption performance is of great importance while remains a big challenge. Herein, cellulose-incorporated imprinted material (CMC-MIPs) with solvent-regulated adsorption property was designed and synthesized using the functionalized cellulose (CMC-MA) as main cross-linker with the assistance of co-crosslinking agent divinyl benzene for selective adsorption of bisphenol A (BPA). Styrene was used as functional monomer to interact with BPA through π-π stacking interaction. And CMC-MA could interact with BPA by multi-hydrogen bonding to strengthen the binding interaction. Adsorption experiments demonstrated that the obtained CMC-MIPs exhibited high adsorption capacity (16.23 mg/g) and excellent selectivity (imprinting factor: 16.07) towards BPA. And CMC-MIPs can easily adsorb BPA in aqueous solution, while release most of the adsorbed BPA in organic media (i.e., methanol or ethanol), indicating excellent solvent-regulated adsorption/release property. The developed CMC-MIPs were successfully employed for selective adsorption of BPA from milk samples with satisfactory recoveries. The proposed construction strategy will offer new sights on the fabricating the cellulose-introduced imprinted materials with selective adsorption capability for target analytes.

Advances in separation and analysis of aromatic amino acids in food

苯丙酮尿症等代谢病患者因基因缺陷无法正常代谢食物中的芳香族氨基酸(aromatic amino acids, AAA),常规饮食可能会造成永久性生理损伤,低AAA肽是其重要的蛋白质等同物来源。AAA分离分析技术对低AAA肽的制备和检测至关重要。该领域研究者探索了多种高效的吸附、分离材料,从复杂的蛋白质水解液中选择性吸附脱除AAA以制备符合特定氨基酸限量的低AAA肽类食品,或者建立对AAA特异性提取富集的分离分析策略。该文分析了AAA的结构特点与理化性质,总结了近年来基于活性炭、树脂等吸附材料脱除AAA的技术进展,并从样品前处理、手性分离和吸附-传感3个维度综述了二维纳米材料、分子印迹、环糊精、金属有机骨架等材料在AAA分离分析中的应用。通过探讨各类技术的优缺点,为AAA吸附脱除和分离分析技术的进步提供支撑。

ZIF-Based Metal-Organic Frameworks for Cantilever Gas Sensors

Among the different gas sensing platforms, cantilever-based sensors have attracted considerable interest in recent years thanks to their ultra-sensitivity and high-speed response. The gas sensing mechanism in a dynamic cantilever sensor is based on its resonance frequency shift upon adsorption of a gas molecule on the sensor. In order to sensitize the surface of a cantilever, a sensitive receptor material with large surface area is required. Metal-organic frameworks (MOFs) are a class of nanoporous crystalline materials composed of metal ions coordinated to organic linkers. MOFs are promising for gas sensing applications as they have large surface area, rich porosity with adjustable pore size and excellent selective adsorption capability for various gasses.[1] Zeolite imidazole frameworks (ZIFs) are a class of MOFs where metals with tetrahedral coordination (i.e. Zn, Co, Fe, Cu) are the central node and the ligands are imidazolate-based organic molecules.In this work, we developed a ZIF-based thin film for dynamic cantilever gas-sensing applications. We employed a novel atmospheric pressure spatial atomic layer deposition (AP-SALD)[2][3] technique to deposit a ZnO sacrificial layer on the silicon cantilevers. This technique allows the deposition of high-quality films at atmospheric pressure, faster than conventional ALD. The ZnO layer was then converted to a particular ZIF film with desired porosity and size, through a MOF-CVD process.[4] A gas-sensing bench setup was developed for the cantilever actuation and read-out. We present the chemical and morphological properties of the ZIF, as well as the frequency response of the sensor to various gases. The device showed reliable sensitivity to humidity, CO2 and several VOCs.

Highly selective adsorption and efficient recovery of cationic micropollutants from aqueous solution via ultrathin indium vanadate nanoribbons

Seeking adsorbents with high adsorption capacity and ease of regeneration is imperative for environmental remediation. Herein, strongly negatively charged two-dimensional (2D) ultrathin InVO4 nanoribbons (NRs) were synthesized. The material exhibited impressive selective adsorption capabilities towards cationic dyes, and the fitted Langmuir maximum adsorption capacity is 789.7 mg/g when using RhB as a model signal pollutant. The adsorption curve towards Rhodamine B (RhB) fits well with the pseudo-second-order (PSO) reaction. The corresponding adsorption isotherm is confirmed in accordance with the Freundlich model, indicating the adsorption is likely a multi-layer adsorption process. Through examining its adsorption activities with positively charged upconversion nanoparticles (UCNPs) and dyes with different surface charges, the strong electrostatic attraction is found to be the predominant adsorption mechanism. Furthermore, the new adsorbents showed remarkable resilience to even large pH variation (from 3 to 12), and could be rapidly and efficiently regenerated using a mixture of water and ethanol (volume ratio 1:1) in 30 min. These advantages are highly favorable for the application of efficient adsorbents for wastewater treatment and resource recovery.