Modification Of Carboxyl Groups Research Articles

Effective strategies alleviate mitochondrial toxicity of perfluorooctanoic acid: Modification of functional head group and inhibition of toxic target

Minimizing the detrimental impacts of perfluorooctanoic acid (PFOA) on human health is a daunting task. Here, we aimed to propose effective strategies for reducing PFOA-induced mitochondrial toxicity in human liver and intestinal cells. PFOA could occupy the fatty acid-binding pockets of human peroxisome proliferator-activated receptor alpha (hPPARα). PFOA not only could structurally interact with hPPARα, but also substantially upregulated the expression levels of PPARα and its downstream gene (i.e., pyruvate dehydrogenase kinase (PDK4)). The increased expression of PDK4 was associated with the mitochondrial toxicity of PFOA, and inhibition of PDK4 or knock-down of PDK4 could effectively attenuate the mitochondrial toxicity of PFOA. Moreover, modification of carboxyl group via an esterification of PFOA into methyl perfluorooctanoate (MePFOA) decreased the affinity to hPPARα, resulting in the loss of upregulated expressions of PPARα and PDK4. Lower mitochondrial toxicity and cytotoxicity were found in the MePFOA-treated cells compared to PFOA exposure. Our study supported that the carboxyl group of PFOA (as functional head group) was required for inducing its mitochondrial toxicity. Two strategies, including modification of functional head group and inhibition of toxic target of PFOA, are feasible to ameliorate mitochondrial toxicity of PFOA.

Tribological performance of di-n-octyl sebacate synthesized with carboxylated nano-MoS2/sericite as catalyst

PurposeThis study aims to explore the synthesis and tribological performances of di-n-octyl sebacate (DOS) synthesized with spherical nano-MoS2/sericite (SMS) and carboxylated SMS (CSMS) as catalysts.Design/methodology/approachSMS and CSMS were used as esterification catalysts to synthesize DOS from sebacic acid and n-octanol. The two catalysts were in situ dispersed in the synthesized DOS after the reaction to form suspensions. The tribological performances of the two suspensions after 20 days of storage were studied.FindingsCSMS was more stably dispersed in DOS than SMS, and they reduced friction by 55.6% and 22.2% and wear by 51.3% and 56.5%, respectively. Such results were mainly caused by the COOH on CSMS, which was more conducive to improving the dispersion and friction reduction of CSMS than wear resistance. Another possible reason was the difference between the dispersion amounts of CSMS and SMS in DOS. The sericite of SMS was converted into SiO2 to enhance wear resistance, while that of CSMS only partially generated SiO2, and the rest still remained on the surface to reduce friction.Originality/valueThis work provides a more effective SMS catalytical way for DOS synthesis than the traditional inorganic acid catalytical method. SMS does not need to be separated after reaction and can be dispersed directly in DOS as a lubricant additive. Replacing SMS with CSMS can produce a more stable suspension and reduce friction significantly. This work combined the advantages of surface carboxylation modification and in situ catalytic dispersion and provided alternatives for the synthesis of DOS and the dispersion of MoS2-based lubricant additives.

Hydrophilic chitosan: modification pathways and biomedical applications

Chitosan, a natural and abundant polysaccharide, offers several advantageous properties, such as excellent biocompatibility, biodegradability, and antimicrobial activity, making it a highly versatile material. However, its extensive application is hindered by its insolubility in water and most organic solvents, due to numerous intramolecular/intermolecular hydrogen bonds. To overcome this limitation and optimize its benefits, chitosan is often chemically modified to enhance its utility in various industries. Biomedical materials, environmental management, biological papermaking, food preservation, and the daily chemical industry are a few examples. Modified chitosan retains the inherent properties of chitosan and acquires new physicochemical characteristics as a result of introduced functional groups. Hydrophilic modifications typically include carboxylation, phosphorylation, and quaternary ammonium modification reactions. The specific properties and applications of chitosan derivatives depend on the grafted groups. This review summarizes the reaction conditions, properties, and applications of hydrophilic chitosan derivatives in drug delivery and food preservation, serving as a reference for the development and use of chitosan-based biomaterials. <br>The bibliography includes 128 references.

Effect Mechanism of Electrocardiogram-Based Intravenous Single-Walled Carbon Nanotubes on Cardiac Function

This research was aimed to adopt electrocardiogram (ECG) and other techniques to explore the effects and mechanisms of single-walled carbon nanotubes (SWCNTs) and their carboxylation modification (C-SWCNTs) on cardiac function in rats. The SWCNTs were oxidized to C-SWCNTs by concentrated sulfuric acid and concentrated nitric acid. The morphology, surface charge, surface group, and water dispersibility of the samples were characterized. Subsequently, 40 SD rats in a 1:1:1:1 ratio were assigned into sham (intravenous injection of 5% glucose), SWCNT (intravenous injection of 2 mg/mL SWCNT glucose dispersion), C-SWCNT (intravenous injection of 2 mg/mL C-SWCNT glucose dispersion), and C-SWCNT+YM groups (treatment in C-SWCNT group was supplemented with an additional 1 mg/mL store-operated calcium entry (SOCE) blocker YM-58483/BTP2). The tail arterial pressure of rats in each group was detected. Left heart function and hemodynamics were detected by cardiac color ultrasonography. Heart parameters were detected by ECG lead II, and the pathological morphology of the heart was detected by hematoxylin-eosin staining. The levels of proteins related to the cardiac calcium signaling were detected by western blot. The results showed that the particle size distributions of SWCNTs and C-SWCNTs were uniform, and C-SWCNTs had better water dispersibility and a negatively charged surface. The results of caudal arterial pressure showed that SBP, DBP, and MBP of the caudal arteries in the SWCNT and C-SWCNT groups were markedly superior to those in sham group (P < 0.05). Cardiac function results showed drastic decreases in LVDd, EF, EDV, SV, and CO and great increases in LVDs, AV-BVmax, and PV-BVmax in the SWCNT and C-SWCNT groups relative to sham group (P < 0.05). The ECG results showed that relative to those in sham group, the amplitudes of the P wave and ST segment in the SWCNT and C-SWCNT groups were increased, the QRS and RR intervals were greatly prolonged, and the amplitude of the R wave was greatly decreased (P < 0.05). Western blot results showed that the SWCNT and C-SWCNT groups had drastically increased protein levels of ORAI-1 and STIM-1 in the heart versus sham group (P < 0.05). The changes in various cardiac parameters in C-SWCNT group were more prominent, and the cardiac pathological score increased markedly versus that in SWCNT group. The protein levels of ORAI-1 and STIM-1 increased notably (P < 0.05). The changes in various cardiac parameters in C-SWCNT+YM group were notably enhanced versus those in the SWCNT and C-SWCNT groups, the cardiac pathological score was obviously reduced, and the protein levels of ORAI-1 and STIM-1 were substantially decreased (P < 0.05). SWCNTs and C-SWCNTs both had cardiotoxic effects in rats, and C-SWCNTs had more obvious toxic effects. Nevertheless, the SOCE inhibitor YM-58483/BTP2 was able to enhance C-SWCNT-induced cardiac dysfunction by inhibiting the expression of calcium signaling-related proteins and affecting the changes in ECG parameters.

Chemoenzymatic Installation of Site-Specific Chemical Groups on DNA Enhances the Catalytic Activity.

Functional DNAs are valuable molecular tools in chemical biology and analytical chemistry but suffer from low activities due to their limited chemical functionalities. Here, we present a chemoenzymatic method for site-specific installation of diverse functional groups on DNA, and showcase the application of this method to enhance the catalytic activity of a DNA catalyst. Through chemoenzymatic introduction of distinct chemical groups, such as hydroxyl, carboxyl, and benzyl, at specific positions, we achieve significant enhancements in the catalytic activity of the RNA-cleaving deoxyribozyme 10-23. A single carboxyl modification results in a 100-fold increase, while dual modifications (carboxyl and benzyl) yield an approximately 700-fold increase in activity when an RNA cleavage reaction is catalyzed on a DNA-RNA chimeric substrate. The resulting dually modified DNA catalyst, CaBn, exhibits a kobs of 3.76 min-1 in the presence of 1 mM Mg2+ and can be employed for fluorescent imaging of intracellular magnesium ions. Molecular dynamics simulations reveal the superior capability of CaBn to recruit magnesium ions to metal-ion-binding site 2 and adopt a catalytically competent conformation. Our work provides a broadly accessible strategy for DNA functionalization with diverse chemical modifications, and CaBn offers a highly active DNA catalyst with immense potential in chemistry and biotechnology.

Simulation study of the effect of OGs on the adsorption of formaldehyde on modified activated carbon.

To explore the impact of OGs (OGs) on formaldehyde (HCHO) adsorption by modified activated carbon, this paper studied the influence of OGs on HCHO adsorption characteristics, varying the groups including ester, carboxyl, and hydroxyl. Employing density functional theory (DFT), the effects of various OGs on the structure of N-doped activated carbon through GGA-PBE exchange-correlation functionals by Materials Studio combined with Gaussian software. The types of weak interactions during the adsorption process were calculated by RDG, elucidating the mechanism through which the three OGs affect HCHO adsorption on N-doped activated carbon. The dynamic adsorption process of HCHO was simulated by molecular dynamics (MD). The influence and proportion of OGs on HCHO adsorption were subsequently analyzed using van der Waals and electrostatic interactions, determining differences in formaldehyde adsorption effects across OG types. The carboxyl group exhibits the most robust synergistic adsorption effect on the modified activated carbon. There is a notable alteration in the position and distribution of electrostatic potential extremes observed following carboxyl modification. The calculation results show that the adsorption energy of hydroxyl groups on modified activated carbon is the highest, at -5.07 kcal/mol, with a transfer charge of 0.014 e. Following the introduction of carboxyl groups, the proportion of electrostatic interactions escalated from the initial 24% to 38%. This study will provide new ideas for guiding the design of activated carbon for efficient adsorption of formaldehyde. The modified activated carbon fragments of three OGs were constructed by Materials Studio and Gaussian software, and the surface electrostatic potential polarity and area distribution, charge change, adsorption energy, and transferred charge of each molecular fragment were calculated. Moreover, cell models of OGs with the same dimensions were constructed to simulate the adsorption amount, heat of adsorption, interaction energy, radial distribution function, and hydrogen-bonding interactions for methane at room temperature and pressure. The results were consistent with the DFT simulations.

Carboxyl-functionalized magnetic amide-linked covalent organic framework for efficient extraction of multi-class mycotoxins from soybeans prior to HPLC-MS/MS analysis

Mycotoxins co-contamination in soybean poses great risks to human health, however, due to their diverse structures, it is difficult to simultaneously extract and detect these multi-mycotoxins. By incorporating modification of hydrophilic carboxyl groups with the hydrophobic properties of covalent organic frameworks, a stable cubic carboxyl-functionalized magnetic amide-linked covalent organic framework were fabricated, characterized and utilized as adsorbents for magnetic solid phase extraction (MSPE) of eleven frequently detected mycotoxins from soybeans followed by HPLC-MS/MS analysis. The key MSPE parameters were screened using the Plackett-Burman design and optimized with the Box-Behnken design for response surface methodologies. Under the optimal experimental conditions, the linear range was 0.2–50 μg/kg, the limits of detection were 0.1–1.4 μg/kg. The established method was applied for the soybean analysis with satisfactory recoveries (70.8–108.3%) and precision (intra- and inter-relative standard deviations of 2.1–9.2% and 1.6–11.1%, respectively). With proper modification, this method may have great application potential for simultaneously analyzing and monitoring the multi-mycotoxin contamination in foods to ensure consumer safety and public health.

Ultrasonic-assisted in situ synthesis of MOF-199 on the surface of carboxylated cellulose fibers for efficient adsorption of methylene blue.

A high-efficiency porous adsorbent, MOF-199/carboxylated cellulose fibers (MOF-199/CCF), was synthesized in situ at room temperature through carboxylation modification, simple sonication, and vacuum drying. The sonication method produced small MOF-199 particles (tens of nanometers), which allowed for uniform distribution of MOF-199 on CCF and improved its efficiency. The presence of CCF carriers reduces the agglomeration of MOF-199 and enhances its performance. The BET-specific surface area of MOF-199/CCF is 264.83 m2 g-1, which is much larger than that of CCF (2.31 m2 g-1), proving the successful modification of CCF by MOF-199. MOF-199/CCF exhibits better adsorption capacity than CCF, with an adsorption capacity of 659.6 mg g-1 of methylene blue within 30 minutes, and good recycling performance. This work presents a straightforward method for preparing efficient cellulose-based adsorbent materials and offers a novel approach for synthesizing MOF composites.

Mechanochemistry transforming high-surface-area coal-based activated carbon into densified carbon with optimized multi-scale structures for enhanced sodium/potassium ion storage

Practical sodium/potassium-ion batteries require carbon anodes with both high gravimetric and volumetric performances, for which engineering carbon material with simultaneous high-density architecture and well-organized structures is the key. Herein, a simple and scalable strategy via a mechanochemistry process is developed to transform high-surface-area activated carbon into densified carbon with optimized multi-scale structures in term of greatly decreased ineffective pores, a shorten carbon lattice and modified carboxyl-dominant functional groups. In the mechanochemical process, the rearrangement of ineffective pores was achieved by high-energy collision and shear effects between grinding balls and particles, in which micropores were concentrated at ∼0.5 nm, followed by carboxylic modification on the fresh edges in air atmosphere (CO2). The reduced ineffective pores and enriched functional groups have improved reversibility and kinetics of Na/K ions storage in carbon matrix, resulting in large reversible capacities, excellent rate capabilities even at a high-loading mass of 5 mg·cm−2. Electrochemical kinetic analysis and ex-situ X-ray diffraction reveal the dominant capacitive storage mechanism for Na+, and theorical calculations demonstrate that the grafted carboxyl groups in carbon matrix promote Na+ reversible storage with multi-ion adsorption configuration, thus improving capacitive storage capacities. This work demonstrates the feasibility of transforming coal-based porous carbon into high-performance anode materials.

Interaction of chitosan with nanoplastic in water: The effect of environmental conditions, particle properties, and potential for in situ remediation

Micro- and nanoplastic (MNP) pollution in aquatic ecosystems requires investigation on its source, transport, and extent to assess and mitigate its risks. Chitosan is a potential biomolecule for water treatment, but its interaction with MNP is undefined. In this work, chitosan-nanoplastic interaction was explored in the laboratory under environmentally relevant conditions using polystyrene (PS) nanoplastic (NP) as model particle to identify conditions at which PS-chitosan interaction resulted in aggregation. Aggregation limits NP transport and allows separation of NP for targeted remediation. The effect of environmental conditions (pH, salinity, dissolved organic matter (DOM) content), chitosan particle size and NP surface modification on chitosan-NP interaction was studied at various chitosan doses. PS aggregated at chitosan doses as low as 0.2 % w/w, while higher doses of chitosan resulted in re-stabilization of NP in solution, restoring the particle size to its initial value. Increasing pH, DOM, or carboxyl modification of the NP surface also improved NP stability in solution. Increased salinity of the solution caused aggregation of unmodified PS independent of chitosan, but carboxyl-modified PS remained stable and aggregated at the same chitosan doses across all salinity levels. Chitosan with low molecular weight promoted PS aggregation at lower doses. Notably, zeta potential (ZP) alone did not indicate chitosan-induced PS aggregation, which occurred independently of changes in ZP. DLVO calculations based on ZP, however, still indicated attractive interaction due to charge differences, albeit with less contrast at high pH, salinity, and DOM content. Additional insights gained in the work recommend caution when using spectrophotometric methods to assess NP removal. Overall, this study demonstrates that chitosan impacts NP transport and holds potential for water remediation of NP.

Carboxyl-functionalized covalent organic frameworks for the efficient adsorption of foodborne heterocyclic aromatic amines

The development of sorbents with high sensitivity and specificity for the effective extraction and assessment of carcinogenic heterocyclic aromatic amines (HAAs) in thermally processed foods is of utmost significance for food safety monitoring. Herein, we report the design and synthesis of a carboxyl-functionalized covalent organic framework (COF), TpPa-(COOH)2, through the regulation of carboxyl modification and crystallinity. The resulting flower-like TpPa-(COOH)2 exhibited excellent crystallinity and microporosity in an eclipsed stacking structure. Compared to TpPa, the introduction of carboxyl moieties in TpPa-(COOH)2 provided additional binding sites and significantly enhanced adsorption affinity for the 16 target analytes, despite having a smaller BET surface area. The adsorption of HAAs by TpPa-(COOH)2 followed the pseudo-second-order model and exhibited rapid kinetics (10–30 min). The experimental data demonstrated a strong fit with the Freundlich isotherm model, resulting in a maximum adsorption capacity of HAAs ranging from 1.8 to 155.8 mg/g. Additionally, the presence of interfering compounds only caused a slight reduction in both the equilibrium adsorption capacity and HAAs recovery. Notably, TpPa-(COOH)2 maintained its effective adsorption performance even after three adsorption–desorption cycles. Theoretical calculations indicated that the rapid binding of HAAs to TpPa-(COOH)2 could be attributed to the joint effects of electrostatic interaction, π–π interaction, C–H–π interaction, lone pair–π interaction, and hydrogen bonding. This adsorbent exhibits a notable enhancement in both adsorption capacity and mass transfer rates for the adsorption of HAAs, surpassing the performance of the reported adsorbents. This highlights its substantial potential for the precise detection of HAAs within food systems.

Structure and Properties of Carboxylated Carbon Nanotubes@Expanded Graphite/Polyethersulfone Composite Bipolar Plates for PEM.

Composite bipolar plates (BPs) hinder their application in proton exchange membrane fuel cells (PEMFC) because of their poor conductivity and mechanical properties. Nanofillers can effectively solve this problem but often have a limited effect due to their easy agglomeration. In this work, a continuous mesh carboxylated multi-walled carbon nanotube (MWCNT) coating on the surface of graphite was synthesized by chemical vapor deposition (CVD) and carboxylation modification, and the composite BPs were prepared by molding using prepared reticulated carboxylated MWCNTs, expanded graphite, and resin. By optimizing the carboxylation treatment time and the content of the nano-filler, the composite BPs had the best performance at a 15 min carboxylation treatment time and 2.4% filler content. The planar conductivity reached up to 243.52 S/cm, while the flexural strength increased to 61.9 MPa. The thermal conductivity and hydrophobicity were improved compared with the conventional graphite/resin composite BPs, and good corrosion resistance has been demonstrated under the PEMFC operating environment. This work provides a novel nanofiller modification paradigm for PBs.

Radiation synthesized carboxyl-functionalized covalent organic framework adsorbent for efficient heavy metal decontamination

Carboxyl groups exhibit great potential in the field of heavy metal decontamination due to their good coordination ability. In this work, acrylic acid was grafted onto covalent organic framework (COF) by using a γ-ray radiation grafting approach. A carboxyl-functionalized adsorbent designated AA-TbDa-COF with high performance for multiple heavy metal removal was obtained. Infrared spectroscopy and thermogravimetric analysis proved the successful carboxyl modification. The porous nanofiber morphology and high accessibility of carboxyl functional groups give the resultant AA-TbDa-COF ultra-fast adsorption kinetics. The capacity for Pb2+, Cd2+ and Cu2+ decontamination was 127.9, 60.6 and 39.8 mg/g, respectively. The preparation of functional COFs by radiation method is extended to the field of heavy metal treatment, proving the great potential of radiation-prepared materials in environmental governance.

Fabrication of structural defects and carboxyl groups on graphitic carbon nitride with enhanced visible light photocatalytic activity

Structural defects and surface functional group defects engineering in graphitic carbon nitride (g-C3N4) have great significance for optimizing its electron structure and photocatalytic activity. In this study, g-C3N4 was prepared via a solvothermal method without high-temperature calcination, and then carboxyl group defects-containing g-C3N4 was synthesized through post-modification. FTIR and XPS verified the presence of highly favorable carboxyl groups. Morphological and photoelectrical experiments verified that adding branched chains with carboxyl groups onto g-C3N4 effectively increased the specific surface area and pore volume of g-C3N4, improved the absorption of visible light and enhanced the separation and migration of photogenerated carriers. As a result, the modified g-C3N4 (CN-COOH) had a high bisphenol A (BPA) photocatalytic degradation of 99.6% at 60 min and a high kinetics constant of 0.067 min−1, which was 13.4 times that of the original g-C3N4 under visible light irradiation. In addition, CN-COOH showed high photocatalytic stability with photocatalytic activity decreased by only 1.5% after 5 cycles. Active species capture experiments have demonstrated that •O2− and holes are the main active substances in the BPA photocatalytic process. These findings open a new avenue for precise carboxyl modification of g-C3N4 via an environmentally-friendly post-modification approach and provide the mechanism of carboxyl defects of g-C3N4 photocatalysts on prompting photogenerated charge separation.

Biocompatibility and Biological Effects of Surface-Modified Conjugated Polymer Nanoparticles.

Semiconductiong polymer nanoparticles (Pdots) have a wide range of applications in biomedical fields including biomolecular probes, tumor imaging, and therapy. However, there are few systematic studies on the biological effects and biocompatibility of Pdots in vitro and in vivo. The physicochemical properties of Pdots, such as surface modification, are very important in biomedical applications. Focusing on the central issue of the biological effects of Pdots, we systematically investigated the biological effects and biocompatibility of Pdots with different surface modifications and revealed the interactions between Pdots and organisms at the cellular and animal levels. The surfaces of Pdots were modified with different functional groups, including thiol, carboxyl, and amino groups, named Pdots@SH, Pdots@COOH, and Pdots@NH2, respectively. Extracellular studies showed that the modification of sulfhydryl, carboxyl, and amino groups had no significant effect on the physicochemical properties of Pdots, except that the amino modification affected the stability of Pdots to a certain extent. At the cellular level, Pdots@NH2 reduced cellular uptake capacity and increased cytotoxicity due to their instability in solution. At the in vivo level, the body circulation and metabolic clearance of Pdots@SH and Pdots@COOH were superior to those of Pdots@NH2. The four kinds of Pdots had no obvious effect on the blood indexes of mice and histopathological lesions in the main tissues and organs. This study provides important data for the biological effects and safety assessment of Pdots with different surface modifications, which pave the way for their potential biomedical applications.

Synthesis of Hollow Calcium Carbonate Microspheres by a Template Method for DOX Loading and Release with Carbon Dots Photosensitivity.

Calcium carbonate, as the main inorganic component of human bones and teeth, has good biocompatibility and bioactivity and finds increasing applications in the field of bone drug carriers. In this study, hollow calcium carbonate microspheres were synthesized by a water hydrothermal method using folic acid as a template. Before drug loading, the prepared calcium carbonate microspheres were subjected to aminidation, carboxylation, and vinylenimine modification. The hollow calcium carbonate microspheres loaded with doxorubicin hydrochloride (DOX) were further incorporated with light-emitting carbon quantum dots(CQDs) and hyaluronic acid (HA). The result showed that the drug loading capacity in the as-prepared calcium carbonate was 179.064 mg/g. In the simulated solutions of cellular metabolism containing various concentrations of reduced glutathione(GSH), the sustained release of DOX was confirmed qualitatively by the luminescence of the CQDs. The DOX release rate was measured quantitively by UV absorption spectra. The highest release rate reached 85.99% in a simulated solution of 0.005 mol/L GSH solution, and the release rate could vary intelligently with the concentration.

Thermal Stability of Self-Assembled 3-Aminopropyltrimethoxysilane Diffusion Barrier Terminated by Carboxyl Groups

The carboxyl-terminated 3-aminopropyltrimethoxysilane (APTMS) self-assembled monolayer (SAM) diffusion barrier was prepared onto a Si substrate via molecular self-assembly and graft modification technology. The SAM was afterward coated with a copper film via radio-frequency (RF) magnetron sputtering. In order to study the thermal stability of the diffusion barrier, the sample was subsequently annealed for 60 min in an Ar environment at the temperatures of 350 °C, 400 °C, 450 °C, 500 °C, and 550 °C. The results revealed that carboxyl modification enabled one to increase the barrier breakdown temperature of the APTMS diffusion barrier layer by about 100 °C, which was sufficient to effectively inhibit the copper diffusion at 500 °C.

Room-temperature hydrogen storage performance of metal-organic framework/graphene oxide composites by molecular simulations

Metal-organic framework/graphene oxide (MOF/GO) composites have been regarded as potential room-temperature hydrogen storage materials recently. In this work, the influence of MOF structural properties, GO functional group contents and different amounts of doped lithium (Li+) on hydrogen storage performance of different MOF/GO composites were investigated by grand canonical Monte Carlo (GCMC) simulations. It is found that MOF/GO composites based on small-pore MOFs exhibit enhanced hydrogen storage capacity, whereas MOF/GO based on large-pore MOFs show decreased hydrogen storage capacity, which can be ascribed to the novel pores at MOF/GO interface that favors the enhanced hydrogen storage performance due to the increased pore volume/surface area. By integrating the small-pore MOF-1 with GO, the hydrogen storage capacity was enhanced from 9.88 mg/go up to 11.48 mg/g. However, the interfacial pores are smaller compared with those in large-pore MOFs, resulting in significantly reduced pore volume/surface area as well as hydrogen storage capacities of large-pore MOF/GO composite. Moreover, with the increased contents of hydroxyl, epoxy groups as well as carboxyl group modification, the pore volumes and specific surface areas of MOF/GO are decreased, resulting in reduced hydrogen storage performance. Furthermore, the room-temperature hydrogen storage capacities of Li+ doped MOF/GO was improved with increased Li+ at low loading and decrease with the increased Li+ amounts at high loading. This is due to that the introduced Li+ effectively increases the accessible hydrogen adsorption sites at low Li+ loading, which eventually favors the hydrogen adsorption capacity. However, high Li+ loading causes ion aggregation that reduces the accessible hydrogen adsorption sites, leading to decreased hydrogen storage capacities. MOF-5/GO composites with moderate Li+ doping achieved the optimum hydrogen storage capacities of approximately 29 mg/g.

H2+CO2 Synergistic Plasma Positioning Carboxyl Defects in g-C3N4 with Engineered Electronic Structure and Active Sites for Efficient Photocatalytic H2 Evolution.

Defective functional-group-endowed polymer semiconductors, which have unique photoelectric properties and rapid carrier separation properties, are an emerging type of high-performance photocatalyst for various energy and environmental applications. However, traditional oxidation etching chemical methods struggle to introduce defects or produce special functional group structures gently and controllably, which limits the implementation and application of the defective functional group modification strategy. Here, with the surface carboxyl modification of graphitic carbon nitride (g-C3N4) photocatalyst as an example, we show for the first time the feasibility and precise modification potential of the non-thermal plasma method. In this method, the microwave plasma technique is employed to generate highly active plasma in a combined H2+CO2 gas environment. The plasma treatment allows for scalable production of high-quality defective carboxyl group-endowed g-C3N4 nanosheets with mesopores. The rapid H2+CO2 plasma immersion treatment can precisely tune the electronic and band structures of g-C3N4 nanosheets within 10 min. This conjoint approach also promotes charge-carrier separation and accelerates the photocatalyst-catalyzed H2 evolution rate from 1.68 mmol h−1g−1 (raw g-C3N4) to 8.53 mmol h−1g−1 (H2+CO2-pCN) under Xenon lamp irradiation. The apparent quantum yield (AQY) of the H2+CO2-pCN with the presence of 5 wt.% Pt cocatalyst is 4.14% at 450 nm. Combined with density functional theory calculations, we illustrate that the synergistic N vacancy generation and carboxyl species grafting modifies raw g-C3N4 materials by introducing ideal defective carboxyl groups into the framework of heptazine ring g-C3N4, leading to significantly optimized electronic structure and active sites for efficient photocatalytic H2 evolution. The 5.08-times enhancement in the photocatalytic H2 evolution over the as-developed catalysts reveal the potential and maneuverability of the non-thermal plasma method in positioning carboxyl defects and mesoporous morphology. This work presents new understanding about the defect engineering mechanism in g-C3N4 semiconductors, and thus paves the way for rational design of effective polymeric photocatalysts through advanced defective functional group engineering techniques evolving CO2 as the industrial carrier gas.

Optimized synthesis of molecularly imprinted polymers coated magnetic UIO-66 MOFs for simultaneous specific removal and determination of multi types of macrolide antibiotics in water

Macrolide antibiotics (MALs) are widely used in various fields and are resistant to degrade in the water environment, thus constituting potential hazards to human health. In this work, a new composite, molecularly imprinted polymers coated magnetic metal-organic frameworks with carboxyl modification (M-UIO-66@MIPs) was selected and characterized, for the simultaneous specific adsorption and determination of five MALs from aqueous solution. It was found that UIO-66-COOH with ligand defects showed better pre-polymerization effect than other matrix materials. The synthesis conditions for the imprinting polymer were optimized via response surface methodology. The characteristics of related materials were studied, and a series of adsorption experiments were carried out. The results showed that the adsorption equilibriums of M-UIO-66@MIPs were reached within 1 h, with the total adsorption capacity for the five MALs was 99.05 mg g−1. The pseudo-second-order kinetic model and Freundlich isotherm model could best fit the adsorption process, and the adsorption thermodynamics was controlled by the change of entropy. Adsorption mechanisms were deduced as hydrogen bonding interaction and electrostatic interaction. In addition, M-UIO-66@MIPs has good selectivity and reusability. Furthermore, a new detection method for the five MALs was developed, using the prepared material as the adsorbent for magnetic solid-phase extraction, coupled with high-performance liquid chromatography. Under the optimal extraction condition, the limits of detection for five MALs were 3.1–44.6 μg L−1, and the recoveries were 92.9–108.7 % in the determination of real water samples. Therefore, the M-UIO-66@MIPs could be the efficient adsorbent for simultaneous selective removal and sensitive determination of multi-residual MALs.