Donor-acceptor Structure Research Articles

Alkyl chain regulation of charge separation efficiency in edge-grafted g-C3N4 with carboxyl-alkyl substituted polythiophene for enhanced 2-mercaptobenzothiazole photodegradation

To investigate the effect of alkyl chain on the charge separation of photocatalyst, three mono-component edge-grafted g-C3N4 with carboxyl-substituted polythiophenes (CN-CSPs) were designed and synthesized, which chemically anchored polythiophenes to the edge of g-C3N4 framework by amide bond. Theoretical calculations reveal that the donor-acceptor (D-A) structure of the CN-CSPs positions the HOMO at the CSP donor and the LUMO at the heptazine ring acceptor, effectively enhancing intramolecular charge separation. Moreover, the alkyl chain connecting thiophene units to carboxyl groups significantly alters the electronegativity of the carboxyl groups, thereby influencing the dipole moment (DM). An increase in DM correlates with stronger intramolecular charge separation. The DM values of the CN-CSPs rank in the following order: CN-Me(5) (without alkyl) < CN-Et(3) (linear alkyl) < CN-Ma(3) (branched alkyl), consistent with the increasing order of their photocatalytic performance. This modification led to a 17-fold increase in the photocatalytic degradation of 2-mercaptobenzothiazole by the modified CN-Ma(3) compared to pure CN, demonstrating significant cyclic stability and overall enhanced performance of the photocatalytic system. The insights from this study offer valuable guidance for the chemical modification of g-C3N4 to boost photocatalytic efficiency.

A new Conjugated mesoporous polymer as fluorescence sensor for the detection of nerve agent simulant dimethyl chlorophosphonate via specific nucleophilic substitution reaction

Conjugated micro/mesoporous polymers (CMPs) represent a category of porous organic materials formed via covalent bonds. Here, DAC-TFP CMP was synthesized using 3,6-diaminocarbazole (DAC) and 2-hydroxy-1,3,5-benzenetricarbaldehyde (TFP) as building blocks. DAC-TFP CMP is a porous conjugation polymer with remarkable thermal and chemical stability. DAC-TFP CMP suspension demonstrates selective "on-off" fluorescence response towards nerve agent simulant dimethyl chlorophosphonate (DMCP) in 1,4-dioxane with exceptionally low detection limits. DMCP and DAC-TFP CMP undergo a nucleophilic substitution reaction, leading to the formation of an N-P bond between N atom on carbazole of DAC-TFP CMP and P atom of DMCP. The new polymer DAC-TFP CMP@DMCP has electron donor-acceptor structure and the fluorescence quenching can be ascribed to the intramolecular charge transfer (ICT) from DAC-TFP CMP unit to DMCP group, as supported by XPS results and DFT calculation. Upon the addition of DMCP to the 1,4-dioxane suspension of DAC-TFP CMP, a subtle blue shift is observed in both the fluorescence emission spectra and UV-vis absorption spectra, providing further validation of the ICT mechanism. DAC-TFP CMP shows excellent recoveries in detecting DMCP in both soil and pesticide samples containing mesotrione and atrazine, highlighting its strong potential as a reliable chemosensor for DMCP detection and analysis.

Dimeric BODIPY Donors Based on the Donor–Acceptor Structure for All-Small-Molecule Organic Solar Cells

Dimeric BODIPY Donors Based on the Donor–Acceptor Structure for All-Small-Molecule Organic Solar Cells

One pot synthesis of donor-acceptor carbon nitride with distinct thiophene rings accelerate photocatalytic hydrogen evolution

Graphitic carbon nitride (g-CN) with a donor-acceptor structure was synthesized by urea and cross-linking thiophene precursors at the terminal sites, achieved through calcination of urea with four different thiophene-based precursors under atmospheric conditions. Among these, UDB-2-1, which incorporates dibenzothiophene-2-carboxyaldehyde (DB-2) 1 mg, demonstrated a hydrogen evolution activity of 650 μmol/g·h, approximately six times higher than pristine graphitic carbon nitride (U). The apparent quantum yield (AQY) was measured to be 4.01 %, 4.89 %, and 3.72 % at 400 nm, 420 nm, and 450 nm, respectively, in the presence of potassium hydrogen phosphate (KPH). This enhanced performance is attributed to increased visible light absorption from the n-π∗ transition introduced by the thiophene ring and enhanced charge separation due to the donor-acceptor (DA) structure, with DB-2 acting as an electron donor. Prepared photocatalysts were characterized by XRD, XPS, FTIR, SEM, TEM, BET, ESR, EIS, Mott-Schottky, DRS, PL, and TRPL measurement. This study provides a simple and effective strategy to improve carbon nitride performance and underscores the importance of functional group positioning and structural isomers in molecular design for solar-energy applications.

Highly Efficient Near-Infrared Luminescent Radicals with Emission Peaks over 750 nm.

Purely organic molecules exhibiting near-infrared (NIR) emission possess considerable potential for applications in both biological and optoelectronic technological domains, owing to their inherent advantages such as cost-effectiveness, biocompatibility, and facile chemical modifiability. However, the repertoire of such molecules with emission peaks exceeding 750 nm and concurrently demonstrating high photoluminescence quantum efficiency (PLQE) remains relatively scarce due to the energy gap law. Herein, we report two open-shell NIR radical emitters, denoted as DMNA-Cz-BTM and DMNA-PyID-BTM, achieved through the strategic integration of a donor group (DMNA) onto the Cz-BTM and PyID-BTM frameworks, respectively. We found that the donor-acceptor molecular structure allows the two designed radical emitters to exhibit a charge-transfer excited state and spatially separated electron and hole levels with non-bonding characteristics. Thus, the high-frequency vibrations are effectively suppressed. Besides, the reduction of low-frequency vibrations is observed. Collectively, the non-radiative decay channel is significantly suppressed, leading to exceptional NIR PLQE values. Specifically, DMNA-Cz-BTM manifests an emission peak at 758 nm alongside a PLQE of 55 %, whereas DMNA-PyID-BTM exhibits an emission peak at 778 nm with a PLQE of 66 %. Notably, these represent the pinnacle of PLQE among metal-free organic NIR emitters with emission peaks surpassing 750 nm.

Construction of g-C3N4-based donor-acceptor conjugated copolymer for photocatalytic selective oxidation of biomass-derived 5-hydroxymethylfurfural under visible light

Donor-acceptor structure porous nanosheets CNSA-x (x denotes the amount of salicylic acid) were prepared by co-thermal condensation polymerization of aromatic compound salicylic acid (SA) and prepolymer melamine. A variety of characterization methods have been used to thoroughly analyze the morphology, structure, optical and electrical features of the synthesized catalysts. It turned out that the introduction of SA promotes the formation of pore structure and an enhanced specific surface area, which resulted in more reactive sites. Moreover, the introduction of SA improves light absorption capacity and effectively adjusts the valence band position. Meanwhile, it also extends the delocalization system, thereby promoting the migration and separation of photogenerated electron-hole pairs. The catalyst exhibited high performance and stability in the photocatalytic oxidation of 5-hydroxymethylfurfural (HMF) under the synergies of these advantages. Additionally, the elucidation of active reaction species and proposed reaction mechanism enriched the understanding of the catalytic process.

Synthesis of Quinone‐Amine‐Linked Covalent Organic Frameworks for Boosting the Photocatalytic Removal of Uranium

AbstractCompared to imine covalent organic frameworks (COFs), the superior stability of amine‐linked COFs renders them more suitable for long‐term harsh real‐world environments. Their numerous amine sites can serve as functional groups or be subjected to post‐modification to further enhance the performance of the material. However, the assortment and abundance of amine‐linked COFs via currently lacking due to restricted monomer varieties and synthetic methods. Herein, this study presents an innovative approach for synthesizing quinone‐amine‐linked COFs by directly combining 2,5‐dihydroxy‐1,4‐benzoquinone (DHBQ) with various amine monomers and introduce a novel photocatalyst, DHBQ‐TAPP‐COF, specifically tailored to efficiently reduce uranium in harsh environments. DHBQ‐TAPP‐COF features a unique donor–acceptor structure, with the DHBQ units serving as acceptors because they contain abundant oxygen atoms that facilitate metal ion coordination, thereby enhancing charge carrier separation, carrier utilization, and uranium reduction efficiency. The quinone‐amine linkages offer improved stability, extended π‐conjugation, heightened local polarity, and conductivity, which enable efficient carrier transfer within the material and thus enhance the overall performance of the uranium photocatalyst. The proposed photocatalyst can efficiently reduce U(VI) without sacrificial agents or decomposition to precipitate UO2 at a recovery rate exceeding 98%. This catalyst provides an efficient and convenient strategy for the stable and high‐performance photocatalytic reduction of uranium.

Investigating perimidine precursors for the synthesis of new multiredox polymers

We present a new simple approach for electrochemical synthesis of semi-condensed ambipolar perinone polymers with phthaloperine (p1) or phenanthroline (p2) skeleton from available and cheap perimidine precursors. Polymerization of perimidine derivatives varies in efficiency depending on the monomer, but overall is highly efficient, especially when electropolymerization is used. Electrooxidation is well controllable and provides a certain characteristic share of new bonds in the structure of perimidine polymers: semi-ladder bis-perimidine unit, ladder bis-perimidine unit, and protonated bis-perimidine unit. Polymer p2 obtained with higher efficiency was put through broader analysis (UV–Vis, IR, ESR and quantum-chemical calculations). As indicated, donor–acceptor structure and specific intermolecular interactions of p2 assure its electrical conductivity and complex redox activity. Although protonated bonds break π-conjugation in the structure of the macromolecule, there is also a diradical state that favors intermolecular interactions and intermolecular π-conjugation channels within bis-perimidine segments. It has been proven that there is a diradical state which appears as an intermediate state between the oxidized and reduced states of the protonated polymer unit. This work positions perimidine polymers as a versatile ambipolar multiredox p- and n-type conductor, indicating a potential for expanding perinone-based perylene-diperimidine polymers for innovative electronics and (bio)sensors.

Aggregation-Induced Enhanced Electrochemiluminescence Resonance Energy Transfer Biosensor for Ultrasensitive Detection of Carcinoembryonic Antigen Based on Donor-Acceptor Organic Nanoparticles.

Aggregation-induced electrochemiluminescence (AIECL) combines the merits of aggregation-induced emission (AIE) and electrochemiluminescence (ECL), which has become a research hot spot in recent years. Therefore, we synthesized a novel AIE compound (Z)-3-(4-(2-butyl-1,3-dioxo-2,3-dihydro-1H-benzo[de]isoquinolin-6-yl)phenyl)-2-(4-(1,2,2-triphenylvinyl)phenyl)acrylonitrile (TPENI) with a donor-acceptor (D-A) structure, that is, a simple peripheral modification of 4-(2-butyl-1,3-dioxo-2,3-dihydro-1H-benzo[de]isoquinolin-6-yl) benzaldehyde (NI-CHO) with AIE-active tetraphenylethylene (TPE) to achieve the transition of NI-CHO from aggregation-caused quenching (ACQ) to an AIE molecule. When TPENI was in the aggregated state, the luminescence intensity was significantly enhanced due to the TPE structural unit restricting the free rotation of the intramolecular benzene ring, as well as the π-π stacking interactions of the molecules, which was conducive to the preparation of TPENI NPs as ECL materials. Satisfactorily, we found that the ECL intensity of TPENI NPs was increased by about 4.8-fold compared with that of the molecules dispersed in organic solution, and the stability reached about 1000 s. Based on the excellent ECL properties of TPENI NPs, an "on-off-on" ECL biosensor with a wider detection range (1 fg/mL to 100 ng/mL) and a lower detection limit of 0.20 fg/mL (S/N = 3) was proposed for sensitive analysis of a carcinoembryonic antigen (CEA). Overall, this work provided a new approach to the realization of AIECL and laid the foundation for the application of naphthalimide derivatives in ECL.

Highly crystalline benzothiadiazole covalent organic framework for enhanced Cr(VI) photocatalytic reduction by constructing donor-acceptor structure

Covalent organic frameworks (COFs) have gained significant attention in environmental remediation. In this paper, we synthesized two sp2 carbon-conjugated COFs (HDU-107 and HDU-108) using [1,1′:4′,1''-terphenyl]-4,4''-dicarbonitrile and 2,2′-(benzo[c][1,2,5]thiadiazole-4,7-diylbis(4,1-phenylene))diacetonitrile as the core, and benzo[1,2-b:3,4-b′:5,6-b″]trithiophene-2,5,8-tricarbaldehyde as the linker, for efficient photocatalytic reduction of Chromium (VI) (Cr(VI)). HDU-108 successfully constructed an electron donor-acceptor (D-A) structure using electron-rich thiophene as the electron donor and benzothiadiazole as the acceptor, exhibiting excellent photocatalytic ability due to its structure, which facilitated the spatial separation of charge carriers and reduced charge complexation. This ability was far superior to that of HDU-107. For 10 mg of HDU-108, the efficiency of Cr(VI) reduction in 120 minutes was more than 99.9 %. And the cycle experiments confirmed its good reusability and stability. e- played a dominant role in the photoreduction of Cr(VI). Moreover, density-functional theory (DFT) simulations indicated that constructing D-A structures was an effective strategy for modulating photocatalytic activity. The charge separation was triggered by the polarization of the electron-rich BTT nucleus to the local charge density, while the cyanine conjugation provided the active center to concentrate the electronegativity. In conclusion, HDU-108, is expected to be a highly efficient photocatalytic material for environmental remediation.

Donor-acceptor type of triazine-based conjugated organic polymers with excellent charge separation for efficient photocatalytic production of hydrogen peroxide

Hydrogen peroxide (H2O2) was widely utilized as an environmentally friendly and efficient chemical in various fields. The photocatalytic production of H2O2 using conjugated organic polymers as photocatalysts is promising. However, conjugated organic polymers have limited applications due to the high recombination rate of photogenerated carriers, poor electron mobility rate, and long synthesis time. Herein, we rapidly prepared a novel triazine-based conjugated organic polymer (CTP-TT) for efficient photocatalytic production of H2O2 using a facile sonochemical method. The H2O2 photosynthesis rate of CTP-TT reached 3383 μmol · g−1·h−1 in pure water without the addition of sacrificial agents. The experimental and characterization results confirmed that CTP-TT possessed dual H2O2 production pathways of 2e− oxygen reduction reaction (ORR) and 2e− water oxidation reaction, with 2e− ORR dominating. The theoretical calculations indicated that the excellent charge separation efficiency of CTP-TT was due to its unique donor–acceptor structure. This study provides novel design ideas for improving the photocatalytic performance of conjugated organic polymers, which is expected to promote the development of photocatalytic production of H2O2 applications and the rational design and preparation of organic semiconductor photocatalysts.

Boosting photocatalytic performance of polymeric carbon nitride by adjusting its donor-acceptor structure via functional group modification strategy

Solar-driven photodegradation of pollutant is attractive for environmental remediation. Herein, we designed and synthetized a new kind of group-modified polymeric carbon nitride (PCN) photocatalyst with urea and 4-Nitro-o-phenylenediamine by one-pot method and applied to degrade bisphenol A (BPA) in aqueous solution. The light response range of photocatalyst had been extended a lot due to conjugation and electron-withdrawing properties of nitrobenzene. Physical analysis shows that 4-Nitro-o-phenylenediamine grafting brings an improved charge separation capacity. EPR and DFT results demonstrate the charge separation is significantly affected by the donor-acceptor structure of PCN, which can be altered via aromatic electron-withdrawing group. The kinetic constant of photocatalytic degradation for BPA was promoted by 8.8-times greater than unmodified PCN and a good recyclability was achieved. To verify the universality of group modification strategies, we prepared other two kinds of photocatalysts via electron-withdrawing group modification strategy and their photocatalytic performance all had been improved obviously.

Boosting visible-light photocatalytic performance of graphitic carbon nitride by regulating its donor-acceptor structure via maleamide

Graphitic carbon nitride (GCN) has attracted much attention due to its many advantages as a kind of photocatalyst, including low cost, easy to prepare, eco-friendly and so on. However, GCN suffers from limited light-absorption capacity and rapid recombination of photogenerated charge carriers. Herein, a new kind of photocatalyst based on GCN has been synthesized by introducing a small molecule compound (maleamide) through a facile thermal polycondensation method (550 ℃ for 180 min) and applied it to photocatalytic removal of bisphenol A (BPA). The optimized GCN-20 (20 mg maleamide in 10 g urea) exhibits the best BPA degradation performance and good stability. The UV–vis test shows that the introduction of maleamide broadens the optical response threshold of GCN from 435 nm to 460 nm. The promoted photocatalytic performance is mainly attributed to enhanced donor-acceptor structure by electron-withdrawing group, which accelerates charge separation and inhibits recombination of free holes and electrons. The active species including superoxide radicals (⋅O2-), hydrogen peroxide (H2O2) and hydroxyl radicals (⋅OH), play dominant roles in the photocatalytic degradation process.

Inorganic/organic hybrid interfacial internal electric field modulated charge separation of resorcinol-formaldehyde resin for boosting photocatalytic H2O2 production

The strategy of inorganic/organic semiconductor material hybridization is of great significance for the development of highly active photocatalysts. Resorcinol-formaldehyde (RF) resin with a special donor-acceptor (D-A) structure shows excellent performance in the photocatalytic production of H2O2. However, the lack of an internal driving force for the separation and transfer of photogenerated electrons and holes in RF resin greatly limits the performance of H2O2 production. Herein, an inorganic/organic hybrid core-shell structure ZnS@RF photocatalyst was prepared by directionally induced coating of RF resin shells of different thicknesses on the surface of monodisperse ZnS nanospheres. Consequently, the photocatalytic H2O2 performance of ZnS@RF with the optimal RF resin shell thickness reaches 367.9 μmol L−1, which is 69 and 2 times that of ZnS and HRF, respectively. Density functional theory (DFT) calculations and related characterization results collectively demonstrate that the excellent photocatalytic H2O2 production performance of ZnS@RF photocatalyst is mainly attributed to the internal electric field (IEF) formed at the hybrid interface of ZnS and RF heterojunction and the optimization of RF shell thickness, which significantly enhances the separation and transfer of photogenerated carriers and modulates the interfacial catalytic reaction kinetics. This work opens up an avenue for designing inorganic/organic hybrid heterojunction photocatalyst materials with excellent photocatalytic activity.

Deep-blue electroluminescence with orthogonal donor-acceptor structure: The role of charge-transfer excited state component in hybrid local and charge-transfer (HLCT) excited state

In this work, three orthogonally bonded phenanthroimidazole based donor-acceptor (D-A) structured blue-emissive materials N-SBPMCN, N-ABPMCN and N-TBPMCN with different donor moieties are designed synthesized. Theoretical combined experimental researches proved that the involving of weak donor (spiro-fluorene and anthracene) and strong donor triphenylamine can form different locally-emissive (LE) dominated hybrid local and charge-transfer (HLCT) excited state, which can contribute to their high photoluminescent quantum yield (PLQY), satisfied electroluminescence performance and blue purity. Specifically, N-TBPMCN with strong donor triphenylamine that possesses more CT excited state components demonstrates the best electroluminescence performance and blue purity among the three materials, revealing that the molecular design of orthogonal D-A structure is of great potential in blue-emissive functional materials. Additionally, we also discovered that intermolecular CT state can also contribute to high exciton utilization.

(Invited) Synthesis and Optical Properties of Chiral Spiro π-Conjugated Compounds with Donor–Acceptor Structure

Chiral spiro π-conjugated compounds with donor–acceptor structures were synthesized. Carbazol-9-yl, 9,9-dimethylacridin-10-yl, phenoxazin-10-yl donor units were introduced on the spiro-fused acceptor unit with sulfonyl groups. The donor units were found to have great impact on the longest absorption maximum and emission maximum. The chiral spiro π-conjugated compounds with 9,9-dimethylacridin-10-yl or phenoxazin-10-yl donor units showed delayed fluorescence. All of three compounds exhibited circularly polarized luminescence both in solution and solid states.

Vinyl-bearing sp2 carbon-conjugated covalent organic framework composites for enhanced electrochemical performance in hydrogen evolution reaction and lithium–sulfur batteries

Vinyl-bearing triazine-functionalized covalent organic frameworks (COFs) have emerged as promising materials for electrocatalysis and energy storage. Guided by density functional theory calculations, a vinyl-enriched COF (VCOF-1) featuring a donor–acceptor structure was synthesized based on the Knoevenagel reaction. Moreover, the VCOF-1@Ru without pyrolysis was obtained through chemical coordination interactions between VCOF-1 and RuCl3, exhibiting enhanced electrocatalytic performance in the hydrogen evolution reaction when exposed to 0.5 M H2SO4. The results demonstrated that the protonation of VCOF-1@Ru enhanced the electrical conductivity and accelerated the generation of H2 on the catalytically active site Ru. Additionally, VCOF-1@CNT with a tubular structure was prepared by uniformly wrapping VCOF-1 onto carbon nanotubes (CNTs) and using it as a cathode for lithium–sulfur batteries by chemically and physically encapsulating S. The enhanced performance of VCOF-1@CNT was attributed to the effective suppression of lithium polysulfide migration. This suppression was achieved through several mechanisms, including the inverse vulcanization of vinyl on VCOF-1@CNT, the enhancement of material conductivity, and the interaction between N in the materials and Li ions. This study demonstrated a strategy for enhancing material performance by precisely modulating the COF structure at the molecular level.

An efficient “hot exciton” fluorophore based on a dicyanophenanthrene-triphenylamine hybrid

The study presents the design, synthesis, and characterization of DCNP-2TPA, a novel “hot exciton” fluorophore featuring a donor-acceptor structure combining dicyanophenanthrene and triphenylamine. Through a comprehensive analysis including structural examination, theoretical modeling, and optical assessments, the suitability of DCNP-2TPA for integration into organic light-emitting diodes (OLEDs) is evaluated. Comparative to existing dicyanophenanthrene-based emitters, DCNP-2TPA demonstrates significantly enhanced luminescence efficiency, by virtue of the incorporation of two triphenylamine moieties with moderate electron-donating strength. Furthermore, DCNP-2TPA exhibits aggregation-induced emission (AIE) properties and showcases hybridized local and charge-transfer (HLCT) excited states, offering an efficient "hot exciton" channel for triplet harvesting. Employing DCNP-2TPA as the emissive core, OLED devices achieve a noteworthy external quantum efficiency of 8.42 %, highlighting the promise of DCNP-2TPA as an efficient candidate for OLED applications.

Construction and Electrochromic Properties of Two-Dimensional Covalent Organic Frameworks with Donor-Acceptor Structures of Triphenylamine and Bipyridine

The stacking between layers of a two-dimensional covalent organic framework (COF) leads to overlapping π orbitals, which enables charge carriers to be transported quickly through these pre-designed π orbitals. The two-dimensional COF featuring donor-acceptor interactions represents a straightforward approach for fabricating a high-performance organic electrochromic device. In this paper, N, N, N’, N’-tetrad(4-aminophenyl)−1,4-phenylenediamine (TPDA) with electron-rich structure and 2,2’-bipyridine-5,5’-dialdehyde (BPDA) with strong electron absorption ability were used as the construction unit. COFTPDA-BPDA electrochromic materials with donor-acceptor structure were synthesized by Schiff base reaction, which can achieve reversible switching from red to dark gray. The color/fade time of the film at 474 nm wavelength is 6.8 s/11.9 s. The contrast retention rate of the film can reach 97.6% after 20 potential cycles, the memory time is as long as 4278 s. The present study demonstrates that constructing a donor-acceptor (D-A) structural unit with conjugated triphenylamine as the electron donor linked to bipyridine electron-withdrawing groups enhances charge transfer and redox reactions. With the success of this design strategy, the construction of the D-A structure is an important methodology for improving the electrochromic properties of materials.

Strategy to Efficient Photodynamic Therapy for Antibacterium: Donor-Acceptor Structure in Hydrogen-Bonded Organic Framework.

While the construction of a donor-acceptor (D-A) structure has gained great attention across various scientific disciplines, such structures are seldomly reported within the field of hydrogen-bonded organic frameworks (HOFs). Herein, a D-A based HOF is synthesized, where the adjacent D-A pairs are connected by hydrogen bonds instead of the conventionally employed covalent bonds. This structural feature imparts material with a reduced energy gap between excited state and triplet state, thereby facilitating the intersystem crossing (ISC) and boosting the generation rate of single oxygen (quantum yield = 0.98). Consequently, the resulting material shows high performance for antimicrobial photodynamic therapy (PDT). The impact of D-A moiety is evident when comparing this finding to a parallel study conducted on an isoreticular HOF without a D-A structure. The study presented here provides in-depth insights into the photophysical properties of D-A pair in a hydrogen-bonded network, opening a new avenue to the design of innovative materials for efficient PDT.