Enhancing the activity of Pd ensembles on graphene by manipulating coordination environment.

Atomic dispersion of metal catalysts on a substrate accounts for the increased atomic efficiency of single-atom catalysts (SACs) in various catalytic schemes compared to the nanoparticle counterparts. However, lacking neighboring metal sites has been shown to deteriorate the catalytic performance of SACs in a few industrially important reactions, such as dehalogenation, CO oxidation, and hydrogenation. Metal ensemble catalysts (Mn), an extended concept to SACs, have emerged as a promising alternative to overcome such limitation. Inspired by the fact that the performance of fully isolated SACs can be enhanced by tailoring their coordination environment (CE), we here evaluate whether the CE of Mn can also be manipulated in order to enhance their catalytic activity. We synthesized a set of Pd ensembles (Pdn) on doped graphene supports (Pdn/X-graphene where X = O, S, B, and N). We found that introducing S and N onto oxidized graphene modifies the first shell of Pdn converting Pd-O to Pd-S and Pd-N, respectively. We further found that the B dopant significantly affected the electronic structure of Pdn by serving as an electron donor in the second shell. We examined the performance of Pdn/X-graphene toward selective reductive catalysis, such as bromate reduction, brominated organic hydrogenation, and aqueous-phase CO2 reduction. We observed that Pdn/N-graphene exhibited superior performance by lowering the activation energy of the rate-limiting step, i.e., H2 dissociation into atomic hydrogen. The results collectively suggest controlling the CE of SACs in an ensemble configuration is a viable strategy to optimize and enhance their catalytic performance.

Free-standing membrane incorporating single-atom catalysts for ultrafast electroreduction of low-concentration nitrate.

The release of wastewaters containing relatively low levels of nitrate (NO3-) results in sufficient contamination to induce harmful algal blooms and to elevate drinking water NO3- concentrations to potentially hazardous levels. In particular, the facile triggering of algal blooms by ultra-low concentrations of NO3- necessitates the development of efficient methods for NO3- destruction. However, promising electrochemical methods suffer from weak mass transport under low reactant concentrations, resulting in long treatment times (on the order of hours) for complete NO3- destruction. In this study, we present flow-through electrofiltration via an electrified membrane incorporating nonprecious metal single-atom catalysts for NO3- reduction activity enhancement and selectivity modification, achieving near-complete removal of ultra-low concentration NO3- (10 mg-N L-1) with a residence time of only a few seconds (10 s). By anchoring Cu single atoms supported on N-doped carbon in a carbon nanotube interwoven framework, we fabricate a free-standing carbonaceous membrane featuring high conductivity, permeability, and flexibility. The membrane achieves over 97% NO3- removal with high N2 selectivity of 86% in a single-pass electrofiltration, which is a significant improvement over flow-by operation (30% NO3- removal with 7% N2 selectivity). This high NO3- reduction performance is attributed to the greater adsorption and transport of nitric oxide under high molecular collision frequency coupled with a balanced supply of atomic hydrogen through H2 dissociation during electrofiltration. Overall, our findings provide a paradigm of applying a flow-through electrified membrane incorporating single-atom catalysts to improve the rate and selectivity of NO3- reduction for efficient water purification.

High-Efficiency Electrocatalytic Reduction of N2O with Single-Atom Cu Supported on Nitrogen-Doped Carbon.

Nitrous oxide (N2O) is a potent greenhouse gas with a high global warming potential, emphasizing the critical need to develop efficient elimination methods. Electrocatalytic N2O reduction reaction (N2ORR) stands out as a promising approach, offering room temperature conversion of N2O to N2 without the production of NOx byproducts. In this study, we present the synthesis of a copper-based single-atom catalyst featuring atomic Cu on nitrogen-doped carbon black (Cu1-NCB). Attributed to the highly dispersed single-atom Cu sites and the effective suppression of the hydrogen evolution reaction, Cu1-NCB demonstrated an optimal N2 faradaic efficiency (82.1%) and yield rate (3.53 mmol h-1 mgmetal-1) at -0.2 and -0.5 V vs RHE, respectively, outperforming previously reported N2ORR electrocatalysts. Further, a gas diffusion electrode cell was employed to improve mass transfer and achieved a 28.6% conversion rate of 30% N2O with only a 14 s residence time, demonstrating the potential for practical application. Density functional theory calculations identified Cu-N4 as the crucial active site for N2ORR, highlighting the significance of the unsaturated coordination and metal-support electronic structure. O-terminal adsorption of N2O was favored, and the dissociative adsorption (*ON2 → *O + N2) was the rate-determining step. These findings reveal the broad prospects of N2O decomposition via electrocatalysis.

Effects of Ionic Interferents on Electrocatalytic Nitrate Reduction: Mechanistic Insight.

Nitrate, a prevalent water pollutant, poses substantial public health concerns and environmental risks. Electrochemical reduction of nitrate (eNO3RR) has emerged as an effective alternative to conventional biological treatments. While extensive lab work has focused on designing efficient electrocatalysts, implementation of eNO3RR in practical wastewater settings requires careful consideration of the effects of various constituents in real wastewater. In this critical review, we examine the interference of ionic species commonly encountered in electrocatalytic systems and universally present in wastewater, such as halogen ions, alkali metal cations, and other divalent/trivalent ions (Ca2+, Mg2+, HCO3-/CO32-, SO42-, and PO43-). Notably, we categorize and discuss the interfering mechanisms into four groups: (1) loss of active catalytic sites caused by competitive adsorption and precipitation, (2) electrostatic interactions in the electric double layer (EDL), including ion pairs and the shielding effect, (3) effects on the selectivity of N intermediates and final products (N2 or NH3), and (4) complications by the hydrogen evolution reaction (HER) and localized pH on the cathode surface. Finally, we summarize the competition among different mechanisms and propose future directions for a deeper mechanistic understanding of ionic impacts on eNO3RR.

Electrochemical Reduction of Flue Gas Denitrification Wastewater to Ammonia Using a Dual-Defective Cu2O@Cu Heterojunction Electrode.

Wet flue gas denitrification offers a new route to convert industrial nitrogen oxides (NOx) into highly concentrated nitrate wastewater, from which the nitrogen resource can be recovered to ammonia (NH3) via electrochemical nitrate reduction reactions (NITRRs). Low-cost, scalable, and efficient cathodic materials need to be developed to enhance the NH3 production rate. Here, in situ electrodeposition was adopted to fabricate a foamy Cu-based heterojunction electrode containing both Cu-defects and oxygen vacancy loaded Cu2O (OVs-Cu2O), which achieved an NH3 yield rate of 3.59 mmol h-1 cm-2, NH3 Faradaic efficiency of 99.5%, and NH3 selectivity of 100%. Characterizations and theoretical calculations unveiled that the Cu-defects and OVs-Cu2O heterojunction boosted the H* yield, suppressed the hydrogen evolution reaction (HER), and served as dual reaction sites to coherently match the tandem reactions kinetics of NO3-to-NO2 and NO2-to-NH3. An integrated system was further built to combine wet flue gas denitrification and desulfurization, simultaneously converting NO and SO2 to produce the (NH4)2SO4 fertilizer. This study offers new insights into the application of low-cost Cu-based cathode for electrochemically driven wet denitrification wastewater valorization.

Classical and Nonclassical Nucleation and Growth Mechanisms for Nanoparticle Formation.

All solid materials are created via nucleation. In this evolutionary process, nuclei form in solution or at interfaces, expand by monomeric growth and oriented attachment, and undergo phase transformation. Nucleation determines the location and size of nuclei, whereas growth controls the size, shape, and aggregation of newly formed nanoparticles. These physical properties of nanoparticles can affect their functionalities, reactivities, and porosities, as well as their fate and transport. Recent advances in nanoscale analytical technologies allow in situ real-time observations, enabling us to uncover the molecular nature of nuclei and the critical controlling factors for nucleation and growth. Although a single theory cannot yet fully explain such evolving processes, we have started to better understand how both classical andnonclassical theories can work together, and we have begun to recognize the importance of connecting these theories. This review discusses the recent convergence of knowledge about the nucleation and growth of nanoparticles.

Highly Selective Nitrite Hydrogenation to Ammonia over Iridium Nanoclusters: Competitive Adsorption Mechanism.

Wet denitrification is a promising approach to control nitrogen oxides (NOx) produced in fossil fuel combustion. Yet, the highly concentrated nitrite (NO2-) wastewater generated poses a major threat to the aqueous environment. Here, iridium nanoclusters (d = 1.63 nm) deposited on TiO2 were applied for NO2- reduction to ammonia (NRA), showing an exceptional NH4+ selectivity of 95% and a production rate of 20.51 mgN·L-1·h-1, which held significant potential for NO2- wastewater purification and ammonia resource recovery. Notably, an interesting non-first-order NO2- hydrogenation kinetics was observed, which was further confirmed to result from the competitive adsorption mechanism between H2 and NO2- over iridium. The NRA pathways on the Ir(111) surface were explored via density functional theory calculations with the NO2-* → NO* → HNO* → HNOH* → H2NOH* → NH2* → NH3* identified as the most energetically favorable pathway and the NO* → HNO* confirmed as the rate-determining step. In situ DRIFTS further experimentally verified the generation of HNO* intermediate during NO* hydrogenation on Ir(111). To verify NRA kinetics at varied NO2- concentrations or H2 pressures, a kinetic model was derived based on the Langmuir-Hinshelwood competitive adsorption mechanism. These findings provide mechanistic insights into the NRA pathways on Ir nanocatalysts, which will be beneficial for wet denitrification waste stream decontamination and valorization.

Peroxymonosulfate-Based Electrochemical Advanced Oxidation: Complication by Oxygen Reduction Reaction.

Peroxymonosulfate (PMS)-based electrochemical advanced oxidation processes (EAOPs) have received widespread attention in recent years, but the precise nature of PMS activation and its impact on the overall process performance remain poorly understood. This study presents the first demonstration of the critical role played by the oxygen reduction reaction in the effective utilization of PMS and the subsequent enhancement of overall pollutant remediation. We observed the concurrent generation of H2O2 via oxygen reduction during the cathodic PMS activation by a model nitrogen-doped carbon nanotube catalyst. A complex interplay between H2O2 generation and PMS activation, as well as a locally increased pH near the electrode due to the oxygen reduction reaction, resulted in a SO4•-/•OH-mixed oxidation environment that facilitated pollutant degradation. The findings of this study highlight a unique dependency between PMS-driven and H2O2-driven EAOPs and a new perspective on a previously unexplored route for further enhancing PMS-based treatment processes.

Single-Atom Catalysts in Environmental Engineering: Progress, Outlook and Challenges.

Recently, single-atom catalysts (SACs) have attracted wide attention in the field of environmental engineering. Compared with their nanoparticle counterparts, SACs possess high atomic efficiency, unique catalytic activity, and selectivity. This review summarizes recent studies on the environmental remediation applications of SACs in (1) gaseous: volatile organic compounds (VOCs) treatment, NOx reduction, CO2 reduction, and CO oxidation; (2) aqueous: Fenton-like advanced oxidation processes (AOPs), hydrodehalogenation, and nitrate/nitrite reduction. We present the treatment activities and reaction mechanisms of various SACs and propose challenges and future opportunities. We believe that this review will provide constructive inspiration and direction for future SAC research in environmental engineering.

A Protocol for Electrocatalyst Stability Evaluation: H2O2 Electrosynthesis for Industrial Wastewater Treatment.

Electrocatalysis has been proposed as a versatile technology for wastewater treatment and reuse. While enormous attention has been centered on material synthesis and design, the practicality of such catalyst materials remains clouded by a lack of both stability assessment protocols and understanding of deactivation mechanisms. In this study, we develop a protocol to identify the wastewater constituents most detrimental to electrocatalyst performance in a timely manner and elucidate the underlying phenomena behind these losses. Synthesized catalysts are electrochemically investigated in various electrolytes based on real industrial effluent characteristics and methodically subjected to a sequence of chronopotentiometric stability tests, in which each stage presents harsher operating conditions. To showcase, oxidized carbon black is chosen as a model catalyst for the electrosynthesis of H2O2, a precursor for advanced oxidation processes. Results illustrate severe losses in catalyst activity and/or selectivity upon the introduction of metal pollutants, namely magnesium and zinc. The insights garnered from this protocol serve to translate lab-scale electrocatalyst developments into practical technologies for industrial water treatment purposes.

Single-Atom Cobalt Incorporated in a 2D Graphene Oxide Membrane for Catalytic Pollutant Degradation.

We introduce a new graphene oxide (GO)-based membrane architecture that hosts cobalt catalysts within its nanoscale pore walls. Such an architecture would not be possible with catalysts in nanoscale, the current benchmark, since they would block the pores or alter the pore structure. Therefore, we developed a new synthesis procedure to load cobalt in an atomically dispersed fashion, the theoretical limit in material downsizing. The use of vitamin C as a mild reducing agent was critical to load Co as dispersed atoms (Co1), preserving the well-stacked 2D structure of GO layers. With the addition of peroxymonosulfate (PMS), the Co1-GO membrane efficiently degraded 1,4-dioxane, a small, neutral pollutant that passes through nanopores in single-pass treatment. The observed 1,4-dioxane degradation kinetics were much faster (>640 times) than the kinetics in suspension and the highest among reported persulfate-based 1,4-dioxane destruction. The capability of the membrane to reject large organic molecules alleviated their effects on radical scavenging. Furthermore, the advanced oxidation also mitigated membrane fouling. The findings of this study present a critical advance toward developing catalytic membranes with which two distinctive and complementary processes, membrane filtration and advanced oxidation, can be combined into a single-step treatment.

Elucidating the Role of Single-Atom Pd for Electrocatalytic Hydrodechlorination.

In this study, we loaded Pd catalysts onto a reduced graphene oxide (rGO) support in an atomically dispersed fashion [i.e., Pd single-atom catalysts (SACs) on rGO or Pd1/rGO] via a facile and scalable synthesis based on anchor-site and photoreduction techniques. The as-synthesized Pd1/rGO significantly outperformed the Pd nanoparticle (Pdnano) counterparts in the electrocatalytic hydrodechlorination of chlorinated phenols. Downsizing Pdnano to Pd1 leads to a substantially higher Pd atomic efficiency (14 times that of Pdnano), remarkably reducing the cost for practical applications. The unique single-atom architecture of Pd1 additionally affects the desorption energy of the intermediate, suppressing the catalyst poisoning by Cl-, which is a prevalent challenge with Pdnano. Characterization and experimental results demonstrate that the superior performance of Pd1/rGO originates from (1) enhanced interfacial electron transfer through Pd-O bonds due to the electronic metal-support interaction and (2) increased atomic H (H*) utilization efficiency by inhibiting H2 evolution on Pd1. This work presents an important example of how the unique geometric and electronic structure of SACs can tune their catalytic performance toward beneficial use in environmental remediation applications.

Photothermal Membrane Water Treatment for Two Worlds.

In meeting the increasing need for clean water in both developing and developed countries and in rural and urban communities, photothermal membrane water treatment technologies provide outstanding advantages: For developing countries and rural communities, by utilizing sunlight, photothermal membrane water treatment provides inexpensive, convenient, modular, decentralized, and accessible ways to clean water, which can reduce the consumption of conventional energy (e.g., electricity, natural gas) and the cost of clean water production. In developed countries and urban communities, photothermal membrane water treatment can improve the energy efficiency during water purification. In these water purification processes, the light absorption and light-to-heat conversion of photothermal materials are important factors in determining the membrane efficacy. Nanomaterials with well-controlled structure and optical properties can increase the light absorption and photothermal conversion of newly developed membranes. This Account introduces our recent work on developing scalable, cost-effective, and highly efficient photothermal membranes for four water purification applications: reverse osmosis (RO), ultrafiltration (UF), solar steam generation (SSG), and photothermal membrane distillation (PMD). By utilizing photothermal materials, first, we have demonstrated how sunlight can be used to improve the membrane's resistance to biofouling in RO and UF processes by photothermally induced inactivation of microorganisms. Second, we have developed novel SSG membranes (i.e., interfacial evaporators) that can harvest solar energy, convert it to localized heat, and generate clean water by evaporation. This desalination approach is particularly useful and promising for treatment of highly saline water. These new interfacial evaporators utilized graphene oxide (GO), reduced graphene oxide (RGO), molybdenum disulfide (MoS2), and polydopamine (PDA). The solar conversion efficiency and environmental sustainability of the interfacial evaporators were optimized via (i) novel and versatile bottom-up biofabrication (e.g., incorporation of photothermal materials during bacterial nanocellulose (BNC) growth) and (ii) easy and cost-effective top-down preparation (e.g., modification of natural wood with photothermal materials). Third, we have developed membranes for PMD that incorporate photothermal materials to generate heat under solar irradiation, thus providing a higher transmembrane temperature difference and higher driving force for effective vapor transport, making the membrane distillation process more energy-efficient. Lastly, this Account compares the photothermal membrane applications, summarizes current challenges for photothermal membrane applications, and offers future directions to facilitate the translation of photothermal membranes from the laboratory to large engineered systems by improving their scalability, stability, and sustainability.

Interfacial and Activation Energies of Environmentally Abundant Heterogeneously Nucleated Iron(III) (Hydr)oxide on Quartz.

Poorly crystalline iron(III) (hydr)oxide nanoparticles are ubiquitous in environmental systems and play a crucial role in controlling the fate and transport of contaminants. Yet, the thermodynamic and kinetic parameters, e.g., the effective interfacial (α') and apparent activation (Ea) energies, of iron(III) (hydr)oxide nucleation on earth-abundant mineral surfaces have not been determined, which hinders an accurate prediction of iron(III) (hydr)oxide formation and its interactions with other toxic or reactive ions. Here, for the first time, we report experimentally obtained α' and Ea for iron(III) (hydr)oxide nucleation on quartz mineral surfaces by employing a flow-through, time-resolved grazing incidence small-angle X-ray scattering (GISAXS). GISAXS enabled the in situ detection of iron(III) (hydr)oxide nucleation rates under different supersaturations (σ, achieved by varying pH 3.3-3.6) and temperatures (12-35 °C). By quantitative analyses based on classical nucleation theory, α' was obtained to be 34.6 mJ/m2 and Ea was quantified as 32.8 kJ/mol. The fundamental thermodynamic and kinetic parameters obtained here will advance our fundamental understanding of the surface chemistry and nucleation behavior of iron(III) (hydr)oxides in subsurface and water treatment systems as well as their effects on the fate and transport of pollutants in natural and engineered water systems. The in situ flow-through GISAXS method can also be adapted to quantify thermodynamic and kinetic parameters at interfaces for many important solid-liquid environmental systems.

Correlation between the ovarian status and the androgen sensibility in the cultured Japanese eel, Anguilla japonica.

Different responsive abilities of different types of eels (cultured, cultured feminized, and wild silver eels) during artificial maturation are recognized, and maturity status at the beginning of artificial maturation might be important. Maturity may represented by the distribution pattern of oocyte diameters. Androgens have been demonstrated to stimulate ovarian development in eels. To determine the initial status, operations were performed on eels to identify sex and to sample ovarian tissue. The recovered eels were then treated with 17α-methyltestosterone (17MT), and the responses of individual eels to 17MT were determined by the fold change in the mean oocyte diameter before and after treatment. Sampled ovarian tissues were fixed in Bouin's solution, oocytes were isolated, and the diameter of isolated oocytes was measured. The ovarian status, determined by kernel density estimation (KDE), was presented by the probability density of measured oocyte diameters; compared with histograms, a description method, KDE, provided more subtle information on the investigated ovary. Our data indicated a correlation between the initial ovarian status (density pattern) and the consequence of treatment (change of ovary); we also argued the semelparity of the Japanese eel. Our results supported the hypothesis that the initial ovarian status is an important factor affecting artificial maturation and that androgens could ameliorate the initial status of the eel ovary.

Dissolved Organic Matter Affects Arsenic Mobility and Iron(III) (hydr)oxide Formation: Implications for Managed Aquifer Recharge.

During managed aquifer recharge (MAR), injected water significantly alters water chemistry in an aquifer, affecting arsenic mobility. To elucidate the effects of dissolved organic matter (DOM) on arsenic mobilization during MAR, this bench-scale study examined arsenic mobilization from arsenopyrite (FeAsS, an arsenic-containing sulfide) in the presence of Suwannee River natural organic matter, humic acid, and fulvic acid (SRNOM, SRHA, and SRFA), alginate (Alg), polyaspartate (PA), and glutamate (Glu). Suwannee River DOM (SRDOM) decreased arsenic mobility in the short term (<6 h) via inhibiting arsenopyrite oxidative dissolution, but increased arsenic mobility over a longer experimental time (∼7 days) via inhibiting secondary iron(III) (hydr)oxide precipitation and decreasing arsenic adsorption onto iron(III) (hydr)oxide. In situ grazing incidence small-angle X-ray scattering measurements indicated that SRDOM decreased iron(III) (hydr)oxide nucleus sizes and growth rates. A combined analysis of SRDOM and other proteinaceous or labile DOM (Alg, PA, and Glu) revealed that DOM with higher molecular weights would cause more increased arsenic mobility. These new observations advance our understanding of the impacts of DOM in injected water on arsenic mobility and secondary precipitate formation during MAR, and in other systems where interactions between DOM, arsenic, and iron(III) (hydr)oxides take place.

Effects of sulfate on biotite interfacial reactions under high temperature and high CO2 pressure.

To ensure the safety and efficiency of engineered subsurface operations, it is vital to understand impacts of aqueous chemistries on brine-mineral interactions in subsurface environments. In this study, using biotite as a model phyllosilicate, we investigated the effects of sulfate on its interfacial reactions under subsurface relevant conditions (95 °C and 102 atm of CO2). By making monodentate mononuclear complexes with biotite surface sites, 50 mM sulfate enhanced biotite dissolution by 40% compared to that without sulfate. However, sulfate at lower concentrations than 50 mM did not obviously affect biotite dissolution. In addition, sulfate did not impact secondary mineral precipitation. However, even without any discernible surface morphological change, sulfate adsorption made biotite surfaces more hydrophilic. To provide a more comprehensive perspective on environmentally-abundant ligands, we further comparatively examined the effects of various inorganic (e.g., sulfate and phosphate) and organic ligands (e.g., acetate, oxalate, and phosphonates) on biotite interfacial interactions and assessed their impacts on physico-chemical properties. We found that the presence of phosphate and phosphonates significantly promoted precipitation of Fe- and Al-bearing secondary minerals, but sulfate, acetate, and oxalate did not. Biotite surface wettability was also altered as a result of changes in biotite surface functional groups and surface charges by ligand adsorption: sulfate, oxalate, phosphate, and phosphonate made biotite more hydrophilic, while acetate made it less hydrophilic. This study provides useful new insights into the effects of brine chemistries on brine-mineral interactions, enabling safer and more efficient engineered subsurface operations.

Comparative effects of inorganic and organic nitrogen on the growth and microcystin production of Microcystis aeruginosa.

Nitrogen causes the frequent occurrence of harmful algal blooms and possible microcystin production. The effects of ammonia and alanine (Ala) on the growth and microcystin production of Microcystis aeruginosa were investigated using an isotope tracer ((15)N). The results indicated that Ala was directly used by M. aeruginosa and contributed to biomass formation amounting to 2.1 × 10(7) cells mL(-1) on day 48, compared with only 6.2 × 10(6) cells mL(-1) from ammonia alone. Microcystin-LR production with Ala was less than that of ammonia, which peaked at 50.2 fg cell(-1) on day 6. Liquid chromatographic analysis with tandem mass spectrometry of (15)N-microcystin-LR suggested that (15)N from ammonia was probably synthesized into the arginine residue. By contrast, (15)N from Ala was assimilated into the Ala, leucine, the iso-linked (2R,3S)-3-methylaspartic acid, arginine, and certain unusual C20 amino acid residues. The results represent the forward steps in the determination of the nitrogen forms that fuel toxin production and blooms.

Metal-Organic Framework Coated Devices for Gas Sensing.

The demand for monitoring chemical and physical information surrounding, air quality, and disease diagnosis has propelled the development of devices for gas sensing that are capable of translating external stimuli into detectable signals. Metal-organic frameworks (MOFs), possessing particular physiochemical properties with designability in topology, specific surface area, pore size and/or geometry, potential functionalization, and host-guest interactions, reveal excellent development promises for manufacturing a variety of MOF-coated sensing devices for multitudinous applications including gas sensing. The past years have witnessed tremendous progress on the preparation of MOF-coated gas sensors with superior sensing performance, especially high sensitivity and selectivity. Although limited reviews have summarized different transduction mechanisms and applications of MOF-coated sensors, reviews summarizing the latest progress of MOF-coated devices under different working principles would be a good complement. Herein, we summarize the latest advances of several classes of MOF-based devices for gas sensing, i.e., chemiresistive sensors, capacitors, field-effect transistors (FETs) or Kelvin probes (KPs), electrochemical, and quartz crystal microbalance (QCM)-based sensors. The surface chemistry and structural characteristics were carefully associated with the sensing behaviors of relevant MOF-coated sensors. Finally, challenges and future prospects for long-term development and potentially practical application of MOF-coated sensing devices are pointed out.

Adsorption characteristics of dichloromethane-ethyl acetate/toluene vapor on a hypercrosslinked polystyrene adsorbent.

Dichloromethane (DCM), a typical representative of chlorinated volatile organic compounds (CVOCs), is usually exhausted along with other volatile organic compounds (VOCs), such as toluene and ethyl acetate, in industrial factories. To address the complexity of the components, the large variation in concentration of each component and the water content of the exhaust gases emitted from the pharmaceutical and chemical industries, the adsorption characteristics of DCM, toluene (MB), and ethyl acetate (EAC) vapors on hypercrosslinked polymeric resins (NDA-88) were studied by dynamic adsorption experiments. Furthermore, the adsorption characteristics of NDA-88 for binary vapor systems of DCM-MB and DCM-EAC at different concentration ratios and the nature of the interaction force with the three VOCs were explored. NDA-88 was found to be suitable for treating binary vapor systems of DCM mixed with low concentrations of MB/EAC, and a small quantity of adsorbed MB or EAC would promote the adsorption of DCM by NDA-88, which is attributed to the microporous filling phenomenon. Finally, the influence of humidity on the adsorption performance of binary vapor systems for NDA-88 and the regeneration adsorption performance of NDA-88 were investigated. The presence of water steam shortened the penetration times of DCM, EAC, and MB, regardless of whether it was in the DCM-EAC or DCM-MB two-component systems. This study has identified a commercially available hypercrosslinked polymeric resin NDA-88, which has excellent adsorption performance and regeneration capacity for both single-component DCM gas and a binary mixture of DCM-low-concentration MB/EAC, providing experimental guidance for the treatment of emissions from pharmaceutical and chemical industries by adsorption.