Electron-rich Groups Research Articles

Nitrogen-containing graphene oxide composite with acid resistance and high adsorption selectivity for Nd3+

Due to its high dispersibility in aqueous solution, the application of graphene oxide (GO) for wastewater treatment will cause secondary pollution. To realize its easy separation and recycling, the introduction of electron-rich nitrogen groups onto GO was performed, which can greatly reduce its dispersibility and produce reusable adsorbents with excellent adsorption selectivity. Amino grafted GO composite was prepared by a simple one-step coupling reaction between GO and 4-(1,2,4-triazole-1-yl)aniline (TYA). The as-prepared GO-TYA composite exhibited long-term stability in solution and possessed excellent adsorption selectivity for Nd3+. The GO-TYA composite showed higher adsorption capacity for Nd3+, which was 8.80, 15.96, 20.03 and 20.49 times of the adsorption capacities for La3+, Yb3+, Sm3+ and Eu3+, respectively. Regeneration of GO-TYA composite was carried out in acidic solutions, and its structural integrity maintained even after 10 cycles of adsorption-elution. This study provides a new strategy for the construction of acid-resistant GO-based composites for the efficient and selective recovery of rare earth elements from wastewater.

Simulated adsorption of iodine by an amino-metal-organic framework modified with covalent bonds.

Radioactive iodine in nuclear waste is increasingly harmful to the human body and the environment because of its strong radioactivity, high fluidity, easy solubility in water, and long half-life. It is very important to find clean and economical materials to recover and fix radioactive iodine. In this paper, the amino-metal-organic framework was covalently modified to obtain composite materials to improve the recycling of iodine in the environment. These adsorbents are used to adsorb iodine in water, showing outstanding adsorption performance. The adsorption data are in good agreement with the Langmuir isothermal adsorption model and pseudo-second-order kinetic model, indicating that the adsorption process is mainly monolayer adsorption and chemical adsorption. The two materials showed selective adsorption capacity for iodine in the solution containing multiple competing ions. The adsorption capacity of the covalently modified composite increased from 949.52 to 2157.44 mg/g. Compared with the amino-metal-organic framework, the modified composite contains more electron-rich groups as active sites, and forms charge transfer compounds with iodine to realize chemical adsorption. Through the simulated adsorption of ultra-high-pressure micro-jet, the material has certain working ability under high pressure, which provides a theoretical basis for the future recovery and utilization of iodine under high pressure.

Thiophene α-Chain-End-Functionalized Oligo(2-methyl-2-oxazoline) as Precursor Amphiphilic Macromonomer for Grafted Conjugated Oligomers/Polymers and as a Multifunctional Material with Relevant Properties for Biomedical Applications.

Because the combination of π-conjugated polymers with biocompatible synthetic counterparts leads to the development of bio-relevant functional materials, this paper reports a new oligo(2-methyl-2-oxazoline) (OMeOx)-containing thiophene macromonomer, denoted Th-OMeOx. It can be used as a reactive precursor for synthesis of a polymerizable 2,2’-3-OMeOx-substituted bithiophene by Suzuki coupling. Also a grafted polythiophene amphiphile with OMeOx side chains was synthesized by its self-acid-assisted polymerization (SAAP) in bulk. The results showed that Th-OMeOx is not only a reactive intermediate but also a versatile functional material in itself. This is due to the presence of 2-bromo-substituted thiophene and ω-hydroxyl functional end-groups, and due to the multiple functionalities encoded in its structure (photosensitivity, water self-dispersibility, self-assembling capacity). Thus, analysis of its behavior in solvents of different selectivities revealed that Th-OMeOx forms self-assembled structures (micelles or vesicles) by “direct dissolution”.Unexpectedly, by exciting the Th-OMeOx micelles formed in water with λabs of the OMeOx repeating units, the intensity of fluorescence emission varied in a concentration-dependent manner.These self-assembled structures showed excitation-dependent luminescence as well. Attributed to the clusteroluminescence phenomenon due to the aggregation and through space interactions of electron-rich groups in non-conjugated, non-aromatic OMeOx, this behavior certifies that polypeptides mimic the character of Th-OMeOx as a non-conventional intrinsic luminescent material.

Structure-activity relationship in advanced glycation end products formation inhibitory activity of phlorotannins.

The structure and inhibitory activity of advanced glycation end products (AGEs) formation were studied using six model compounds and seven phlorotannins isolated from brown alga Ecklonia stolonifera. As a result, it was inferred that AGEs formation inhibitory activity was stronger when electron-rich groups were present because of the addition of many oxygen atoms to the phlorotannins.

Biomolecular Regulation of Zinc Deposition to Achieve Ultra-Long Life and High-Rate Zn Metal Anodes.

Aqueous zinc-ion batteries (ZIBs) have been extensively studied due to their inherent safety and high energy density for large-scale energy storage. However, the practical application is significantly limited by the growing Zn dendrites on metallic Zn anode during cycling. Herein, an environmental biomolecular electrolyte additive, fibroin (FI), is proposed to guide the homogeneous Zn deposition and stabilize Zn anode. This work demonstrates that the FI molecules with abundant electron-rich groups (NH, OH, and CO) can anchor on Zn anode surface to provide more nucleation sites and suppress the side reactions, and the strong interaction with water molecules can simultaneously regulate the Zn2+ coordination environment facilitating the uniform deposition of Zn. As a consequence, only 0.5 wt% FI additive enables a highly reversible Zn plating/stripping over 4000 h at 1mA cm-2 , indicating a sufficient advance in performance over state-of-the-art Zn anodes. Furthermore, when applied to a full battery (NaVO/Zn), the cell exhibits excellent capacity retention of 98.4% after 1000 cycles as well as high Coulombic efficiency of 99%, whereas the cell only operates for 68 cycles without FI additive. This work offers a non-toxic, low-cost, effective additive strategy to solve dendrites problems and achieve long-life and high-performance rechargeable aqueous ZIBs.

A comparative study on the activation of persulfate by mackinawite@biochar and pyrite@biochar for sulfamethazine degradation: The role of different natural iron-sulfur minerals doping

In this work, two novel heterogeneous catalysts were prepared by loading natural mackinawite (FeS) and pyrite (FeS2) particles into peanut shell-derived biochar (i.e., FeS@BC and FeS2@BC), and the persulfate (PS) activation processes by these two composites for sulfamethazine (SMT) degradation were systematically examined. After doping natural iron-sulfur ores, the catalytic removal performance of the above two composites were 37.2%–80.0% and 31.0%–35.2% higher than those of their respective original minerals and primitive biochar. Simultaneously, FeS@BC had better catalytic performance than FeS2@BC. The larger specific surface areas, abundant micropores, higher defect degree, better conductivity and FeS crystals favored the release of more iron, resulting in higher reaction stoichiometric efficiency (RSE) value, excellent catalytic activity, and enhanced SMT mineralization. In the FeS@BC/PS system, surface ketonic groups (C = O), Fe(II), and highly active S-thiophene groups all accounted for PS activation. In the FeS2@BC/PS system, C = O groups, Fe(II), highly reductive S2−/Sn2– species, and graphene structure participated in the catalytic reaction. The electron-rich S-thiophenic groups, S2−/Sn2– species, and ketonic moieties could act as electron donors, prompting the regeneration of Fe(II) in the lattice (≡Fe(II)) and solution (Fe2+) by direct or indirect electron transfer. In view of the higher catalytic activity of FeS@BC, we further investigated different influencing factors on SMT degradation, activation mechanism, and degradation pathway of SMT in the FeS@BC/system. Overall, this study would fill the gap in the research on the difference in the catalytic activity of catalysts prepared by loading different natural iron-sulfur minerals onto biochar for persulfate activation.

Design, Synthesis, and Application in OFET of a Quinoxaline-Based D-A Conjugated Polymer.

A novel alternating donor–acceptor polymer PQ1 is designed and synthesized by palladium-catalyzed Stille coupling between quinoxaline as an electron-deficient unit and indacenodithiophene (IDT) as electron-rich groups. Polymer PQ1 presents not only a strong intramolecular charge transfer effect, which is beneficial for the charge transport within single molecules but also a narrow electrochemical band gap and a high highest occupied molecular orbital (HOMO) energy level. In addition, the optical absorption study indicates that the PQ1 film exhibits good aggregation, which is an advantage for the charge transport between neighboring molecules. As a consequence, PQ1 presents p-type semiconductor properties with a high hole mobility of up to 0.12 cm2 V−1 s−1. This study reveals the great potential of quinoxaline-type chromophores in constructing novel organic semiconductors.

S⋯N Conformational Lock Acceptor Based on Indacenodithiophene (IDT) Structure and High Electronegative Terminal End Group.

High-performance organic semiconductors should have good spectral absorption, a narrow energy gap, excellent thermal stability and good blend film morphology to obtain high-performance organic photovoltaics (OPVs). Therefore, we synthesized two IDTz-based electron acceptors in this research. When they were blended with donor PTB7-Th to prepare OPV devices, the PTB7-Th:IDTz-BARO-based binary OPVs exhibited a power conversion efficiency (PCE) of 0.37%, with a short-circuit current density (Jsc) of 1.24 mA cm−2, a fill factor (FF) of 33.99% and an open-circuit voltage (Voc) of 0.87 V. The PTB7-Th:IDTz-BARS-based binary OPVs exhibited PCE of 4.39%, with Jsc of 8.09 mA cm−2, FF of 54.13% and Voc of 1.00 V. The results show the strong electronegativity terminal group to be beneficial to the construction of high-performance OPV devices. Highlights: (1) Two new acceptors based on 5,5′-(4,4,9,9-tetrakis (4-hexylphenyl)-4,9-dihydro-s-indaceno [1,2-b:5,6-b′] dithiophene-2,7-diyl) dithiazole (IDTz) and different end groups (BARS, BARO) were synthesized; (2) BARS and BARO are electron-rich end groups, and the electron acceptors involved in the construction show excellent photoelectric properties. They can properly match the donor PTB7-Th, and show the appropriate surface morphology of the active layer in this work; (3) Compared with IDTz-BARO, IDTz-BARS has deeper LUMO and HOMO energy levels. In combination with PTB7-Th, it shows 4.39% device efficiency, 8.09 mA cm−2 short-circuit current density and 1.00 V open circuit voltage.

Conformational Switch of Benzanilide Derivative Induced by Acid; Effect of Pentafluorobenzoyl Group.

Amide-based molecular switches had its limitation on structural diversities. In this work, we designed and synthesized a series of pentafluorobenzoyl-based benzanilide compounds. The conformational ratio of these compounds in solution was correlated linearly with Hammett's σp value of the substituent on the anilide ring, reflecting the repulsive interaction between the carbonyl group and the electron-rich aryl group. The addition of acid into the solution of 6, bearing pentafluorobenzoyl group, switched the stable amide conformation. In addition, the sizeable rotational barrier of 6 induced by the pentafluorobenzoyl moiety enabled us to monitor the conformational transition by means of 1H NMR spectroscopy.

A tailored ceramic composite separator with electron-rich groups for high-performance lithium metal anode

Ceramic composite separator is more competitive than traditional polyolefin separator in the field of power supply for superior thermal stability and wettability of liquid electrolyte. In this study, we develop a two-steps method that modifies SiO2 with acrylamide (AM) by grafting process and prepare a functional SiO2 composite separator (PE/SiO2-AM). This kind of composite separator exhibits similar size-shrinkage (8.8%) to that of PE/SiO2 composite separator at the tested temperature, lower than 18.1% of bare PE separator, and is electrochemically stable below 4.5 V (vs. Li/Li+). In addition, the Li-symmetric cells employing PE/SiO2-AM composite separator have the lowest overpotential and an improved lithium-ion transference number of 0.44. It is demonstrated from DFT calculation that the electron-rich species of imide group is able to uniformly disperse lithium-ion flux at the interface of electrolyte/lithium anode, and contributes to lithium-ion transport process. After assembling the LiCoO2/Li half cells, the cell with PE/SiO2-AM composite separator displays better cycle performance and higher discharge capacity when compared with other separators. Therefore, functional ceramic separator would be more attractive for next-generation lithium metal battery with high energy density.

Adsorption-photocatalysis processes: The performance and mechanism of a bifunctional covalent organic framework for removing uranium ions from water

Photocatalytic reaction could become an effective way to solve the energy crisis and environmental restoration and governance. Herein, we reported a covalent organic framework (COF-TpBpy) was connected by polyhydroxy-containing unit (Tp) and bipyridine unit (Bpy), which was utilized as photocatalytic semiconductor for photocatalytic detoxification of U(VI). Firstly, TpBpy was comprehensively characterized by physical chemistry (PXRD, SEM, TEM, FT-IR, BET, EA) and photoelectrochemistry (Vis-DRS, M-S plots, photocurrent-time, EIS, PL). Hereafter, the adsorption capacity of TpBpy for U(VI) was investigated by batch adsorption experiment, reaching 455 mg/g within 60 min. The adsorption experimental data conformed to the second-order kinetics, suggesting the chemisorption or surface complexation mechanism. Following that, TpBpy exhibited the narrower optical band gap (Eg = 2.2 V, ECB = -0.95 and EVB = 1.25 V vs. NHE) due to its extended π-conjugation system and electron-rich units of the skeleton (N-14.56%, O-27.73%). After visible light irradiation for 420 min, the photoreduction removal rate of U(VI) by TpBpy was about 55.4%. ESR spectra corroborated that O2– radicals and photoelectrons were the main active species involved in the photoreduction process. XPS analysis revealed the formation of NU bond and UO bond, whether in the process of adsorption or photoreduction. In short, the structure of TpBpy possessed strong coordination ability with U(VI) ions, and promoted the transfer of electrons from electron-rich groups to U(VI), thereby reducing to U(IV). As a multifunctional material, TpBpy possess the advantage in eliminating nuclear waste streams.

Unravelling the mechanism of cobalt (II) catalyzed O-arylation reaction between aryl halides and phenols: A DFT study

A detailed theoretical investigation into the mechanism of the cobalt (II) catalyzed O-arylation reaction of phenols with aryl iodides has been carried out with the aid of the Density Functional Theory method at the UB3LYP-D3 level of theory. The naturally occurring amino acid, l-valine was taken as the ancillary ligand for modeling the reaction mechanism. A tetrahedral, l-valine ligated cobalt (II) phenoxide complex in the quartet state, was found to be the active catalytic species. Unlike the Cu-catalyzed C-X (X = O, S, N) cross-coupling and Co-catalyzed CN coupling, the reaction proceeds through a facile σ – bond metathesis mechanism through the concerted breaking of Csp2 – I bond and the formation of Csp2 – O bond. The high reaction barrier (33.60 kcal/mol) obtained for the model system agrees with the experimental requirement of an elevated temperature [1]. To rationalize the experimentally observed selectivity of electron-deficient aryl iodides, we have investigated the electronic effects of various functional groups in the substrate molecules on the activation barrier of the reaction. This was contemplated by using Hammett correlation studies and Frontier Molecular Orbital analysis (FMO). The FMO analysis suggested that substitution by electron-withdrawing groups (EWG) at the para-position of the aryl iodides, decreases the LUMO energy, thereby decreasing the activation barrier of the reaction. However, in the case of substitution at the para-position of the phenolic moiety in the cobalt-phenoxide complex, the electron-rich groups are more favorable than the electron-withdrawing groups due to the rise in the HOMO energy of the substrate by the former. Thus, the present study can throw light on designing better catalytic systems for O-arylation reactions.

The reaction of an amino-functionalized DPP with acrolein

An aminophenyl-functionalized diketopyrrolopyrrole (DPP) was designed and synthesized to react with acrolein. The cyclization reaction between acrolein and the aminophenyl group resulted in an increase in fluorescence at 612 nm in the emission spectrum, along with an 18 nm blue-shift from 630 to 612 nm. This phenomenon occurred because the formation of a quinolyl group led to the disturbance of photoinduced electron transfer from the electron-rich amine group to the electron-poor DPP core.

Synthesis of electron-rich thiophene triphenylamine based organic material for photodiode applications

In this paper, a new electron-rich π-conjugated organic material, 4,4'-(thiophene-3,4-diyl)bis(N,N-diphenylaniline) (bisTPAT), which contain thiophene skeleton as the central core with bistriphenylamine side groups as the electron-rich unit and/or donor groups at the 3- and 4-positions, was designed for photodiode application. The bisTPAT was efficiently synthesized via the Pd-catalyzed Suzuki coupling reaction between 3,4-dibromo-thiophene (3) and (4-(diphenylamino)phenyl)boronic acid 4. Structural, optical, and chemical features of the bisTPAT material and thin film form -was characterized by NMR, FTIR, HRMS, UV–Vis spectroscopy, and SEM/EDX analysis techniques. Subsequently, bisTPAT/n-Si device fabrication was carried out by using the spin coating method. Current-voltage (I–V) measurements were performed to determine the characteristic properties of the device under different operating conditions. According to I–V measurements taken under illumination conditions, the fabricated device has photoresponse characteristics in the reverse bias region. Therefore, the fabricated device can be employed as a photodiode for optoelectronic applications. Additionally, the photodiode parameters, such as ideality factor (n), barrier height (Φb), series resistance (Rs), photosensitivity (S), photoresponsivity (R), photodetectivity (D*), open-circuit voltage (Voc), and short-circuit current (Isc), were analyzed under the light intensity of 100 mWcm−2. Finally, capacitance-voltage (C–V) measurements were carried out to obtain important information about the diode's interfacial characteristics at different frequencies. The results show that the calculated parameters such as diffusion potential (Vd) and carrier concentration are sensible to frequency changes.

Selective degradation of parachlorophenol using Fe/Fe3O4@CPPy nanocomposites via the dual nonradical/radical peroxymonosulfate activation mechanisms

Metal-carbon composite materials have been regarded as emerging catalysts for peroxymonosulfate (PMS) activation by combining the advantages of both parties. Nevertheless, these novel catalysts usually face the side effect of the complex water matrix, and the PMS activation mechanism need to be further clarified. Herein, we rational synthesized the Fe/Fe3O4@CPPy nanocomposites, and the catalytic performance of PMS activation was evaluated by parachlorophenol (4-CP) degradation. The elevated catalytic activity was observed in the optimal Fe/Fe3O4@CPPy-4/PMS system over a wide temperature (10–45 °C) and pH range (3–9), in which the 4-CP removal rate could achieve up to 98.64% within 10 min, as well as the low leakage of iron (49.0 μg/L). Notably, the normal concentrations of coexisting irons and humic acid in surface water matrix could hardly affect the 4-CP removal efficiency, demonstrating the superior selective oxidation capacity of Fe/Fe3O4@CPPy nanocomposites. A positive correlation was displayed between k values and the content of electron-rich carbonyl group (CO), and the pyridinic N, graphitic N and Fe species also participated in the 4-CP removal, which synergistically resulted in the outstanding performance. Moreover, the O2−, 1O2 and direct electron transfer pathways played a primary role in 4-CP elimination, whereas the SO4−/OH displayed the secondary contribution. Therefore, a dual non-radical/radical PMS activation mechanism was unveiled in the Fe/Fe3O4@CPPy-4/PMS system. This work not only provides a high-activity and well-adjusted PMS catalyst for complicated water matrix, but also elucidates PMS activation mechanism in the metal–carbon composite materials.

Activation of Main‐Group Antimony Atomic Sites for Oxygen Reduction Catalysis

The catalytic activity of main-group metal is hard to promote because of the intrinsic lack of host d orbitals available to be combined. Herein, under the guidance of theoretical predictions, we find atom-dispersed antimony sites (Sb-N4 moieties) can be activated to achieve high oxygen reduction reaction (ORR) activity using a functional group regulation strategy. Correspondingly, we manage to synthesize a main-group Sb single-atom catalysts (SACs) that comprises Sb-N4 active moieties functionalized by epoxy groups in the second microenvironment and incorporated in N-doped graphene (Sb1 /NG(O)). The electron-rich epoxy group can adjust the electronic structure of Sb-N4 active moieties, thereby optimizing the adsorption of the intermediate. The Sb SACs are comparable to industrial Pt/C under alkaline conditions. This discovery provides new opportunities to manipulate and improve the catalytic activity of main-group-element electrocatalysts.

Efficient destruction of humic acid with a self-purification process in an Fe0-FeyCz/Fex-GZIF-8-rGO aqueous suspension

Natural organic matter (NOM) has diverse negative impacts on water purification, however, preventing them occurrence very difficult. Herein, humic acid (10 mg/L), as the main component of NOM, is completely destructed within 120 min in the Fe0-FeyCz/Fex-GZIF-8-rGO air-saturated aqueous suspension without additional energy input, while its mineralization is followed by three kinetic constants within 480 min. During the process, HA was first complexed with Fe0-FeyCz/Fex-GZIF-8-rGO by π-π interaction and H-bonding interaction and cleaved to aromatic compounds and then to alkanes and alcohols with some small acids before 120 min. The electron paramagnetic resonance (EPR) analysis and density functional theory (DFT) calculations confirmed that a strongly polarized alkane-alcohol complex was formed after 150 min with an electron-rich hydroxyl group area in alcohol and an electron-poor alkane area. Moreover, the more electrons of alkane in the complex are delocalized and trapped by O2, with the adsorption of the alkane-alcohol complex on the catalyst surface based on the analyses of both electrochemical impedance spectroscopy (EIS) and chronoamperometry, greatly promoting the surface cleavage and hydrolytic process of alkane in the complex and producing more •OH for pollutant degradation than it does from the HA surface complex, which results in the highest mineralization rate in the period of 150–390 min. Our findings demonstrated that the current system is very promising for complex mixture-containing water purification without additional energy.

Highly Selective Detection of Paraoxon in Food Based on the Platform of Cu Nanocluster/MnO2 Nanosheets.

Selective and sensitive identification of paraoxon residue in agricultural products is greatly significant for food safety but remains a challenging task. Herein, a detection platform was developed by integrating Cu nanoclusters (Cu NCs) with MnO2 nanosheets, where the fluorescence of Cu NCs was effectively quenched. Upon introducing butyrylcholinesterase and butyrylcholine into the system, their hydrolysate, thiocholine, leads to the decomposition of the platform through a reaction between the MnO2 nanosheets and thiol groups on thiocholine. The electron-rich groups on thiocholine can further promote the fluorescence intensity of Cu NCs through host–guest interactions. Adding paraoxon results in the failure of fluorescence recovery and further promotion, which could be utilized for the quantitative detection of paraoxon, and a limit of detection as low as 0.22 ng/mL can be achieved. The detection platform shows strong tolerance to common interference species, which endows its applications for the detection of paraoxon in vegetables and fruit. These presented results not only open a new door for the functionalization of metal nanoclusters but also offer an inspiring strategy for analytic techniques in nanomedicine and environmental science.

Programmed Polyene Cyclization Enabled by Chromophore Disruption.

A new polyene cyclization strategy exploiting β-ionyl derivatives was developed. Photoinduced deconjugation of the extended π-system within these chromophores unveils a contrathermodynamic polyene that engages in a Heck bicyclization to afford [4.4.1]-propellanes. This cascade improves upon the limited regioselectivity achieved using existing biomimetic tactics and tolerates both electron-rich and electron-deficient (hetero)aryl groups. The utility of this approach was demonstrated with the diverted total synthesis of taxodione and salviasperanol, two isomeric abietane diterpenes that were previously inaccessible along the same synthetic pathway.

Identification of a Self-Photosensitizing Hydrogen Atom Transfer Organocatalyst System.

We developed organocatalyst systems to promote the cleavage of stable C-H bonds, such as formyl, α-hydroxy, and benzylic C-H bonds, through a hydrogen atom transfer (HAT) process without the use of exogenous photosensitizers. An electronically tuned thiophosphoric acid, 7,7'-OMe-TPA, was assembled with substrate or co-catalyst N-heteroaromatics through hydrogen bonding and π-π interactions to form electron donor-acceptor (EDA) complexes. Photoirradiation of the EDA complex induced stepwise, sequential single-electron transfer (SET) processes to generate a HAT-active thiyl radical. The first SET was from the electron-rich naphthyl group of 7,7'-OMe-TPA to the protonated N-heteroaromatics and the second proton-coupled SET (PCET) from the thiophosphoric acid moiety of 7,7'-OMe-TPA to the resulting naphthyl radical cation. Spectroscopic studies and theoretical calculations characterized the stepwise SET process mediated by short-lived intermediates. This organocatalytic HAT system was applied to four different carbon-hydrogen (C-H) functionalization reactions, hydroxyalkylation and alkylation of N-heteroaromatics, acceptorless dehydrogenation of alcohols, and benzylation of imines, with high functional group tolerance.