Aromatic Units Research Articles

Deuteration as a General Strategy to Enhance Azobenzene‐Based Photopharmacology

AbstractChemical photoswitches have become a widely used approach for the remote control of biological functions with spatiotemporal precision. Several molecular scaffolds have been implemented to improve photoswitch characteristics, ranging from the nature of the photoswitch itself (e.g. azobenzenes, dithienylethenes, hemithioindigo) to fine‐tuning of aromatic units and substituents. Herein, we present deuterated azobenzene photoswitches as a general means of enhancing the performance of photopharmacological molecules. Deuteration can improve azobenzene performance in terms of light sensitivity (higher molar extinction coefficient), photoswitch efficiency (higher photoisomerization quantum yield), and photoswitch kinetics (faster macroscopic rate of photoisomerization) with minimal alteration to the underlying structure of the photopharmacological ligand. We report synthesized deuterated azobenzene‐based ligands for the optimized optical control of ion channel and G protein‐coupled receptor (GPCR) function in live cells, setting the stage for the straightforward, widespread adoption of this approach.

Supercritical CO2 as effective wheat straw pretreatment for subsequent mild fractionation strategies

The efficient utilization of lignocellulosic biomass in biorefineries is pivotal for the transition to a carbon–neutral society, emphasizing the need for environmentally friendly fractionation techniques. While the extensive use of chemicals in biorefinery operations can yield favorable quantities of specific biomass components, adopting less chemically intense conditions is crucial for holistic methodologies that preserve the inherent potential of all biomass constituents. This study comprehensively investigates the use of supercritical carbon dioxide (sc-CO2) as a green pretreatment to improve subsequent mild fractionation on wheat straw. Sc-CO2 at 300 bars, 100 °C and 70% moisture was found to have minimal impact on the chemical composition and the lignin structure, while there were significant morphological changes as heightened surface area and reduced density. Apart from increasing enzymatic saccharification efficiency, the treatment notably enhanced subsequent mild delignification through alkaline and flow-through organosolv extractions. The combination of the pretreatments enhances the lignin solubilization yields from 49 to 79% for alkaline and 74 to 91% for organosolv extractions, while retaining a high β-O-4 conservation of 49 and 59 linkages per 100 aromatic units, respectively. Additionally, the combined use of sc-CO2 with mild dilute acid pretreatment improved xylose solubilization from 59 to 76 % and enzymatic saccharification from 53 to 90%, albeit with increased lignin condensation. In summary, this study demonstrates the potential of sc-CO2 pretreatment as a versatile tool for biomass valorization within the evolving bioeconomy, by combining enhanced extraction yields with minimal lignin structural impact. Our work thereby highlights the promise of the use of sc-CO2 to contribute to the overall economic potential of improved biorefinery processes.

Maximizing the valorization potential of lignin through optimization of the Soda pulping conditions

The valorization potential of lignin is strongly dependent on the yield that can be obtained during the pulping process as well as its chemical structure. Both of these are determined by factors such as the biomass type, the selected extraction strategy and the employed conditions. Within this study, Miscanthus x giganteus biomass was subjected to systematically varying Soda pulping conditions, i.e., temperature (100 °C – 180 °C), OH– concentration (0.158 mol/L – 1.000 mol/L) and time (60 min – 360 min). These pulping conditions can be combined into a single factor, reflecting the processing severity, which in this work varied from approximately 1 to 5. The resulting black liquor, precipitated lignin, lignin stock solution (i.e., lignin dissolved in the solvent used in the subsequent depolymerization step) and product pool after mild reductive catalytic depolymerization (200 °C, 10 bar H2 initial, 4 h) were thoroughly characterized using a plethora of analysis techniques. Increasing the severity factor of the pulping was found to result in an enhancement of the delignification degree from 25.3 ± 2.6 % to 95.4 ± 9.9 %. However, beyond a severity factor of 3, fragmentation of native ether linkages and condensation reactions start to cause unfavourable changes in the chemical structure of the lignin and depolymerization product pool. Furthermore, these reactions significantly reduce the total mass yield from biomass to depolymerization product pool. An Adaboost model with quadratic base estimator was trained against the experimental data, and subsequently used to optimize the pulping conditions, aiming at a maximum total mass yield with minimal fragmentation and, hence, condensation, of the lignin. The optimum was experimentally validated, which resulted in a lignin with high β-O-4 content (42.7 ± 2.8 linkages per 100 aromatic units) and a total mass yield of 30.9 ± 3.4 wt% and a pulp with a residual lignin content of 8.25 ± 0.94 wt%.

Evolution mechanism of organic macromolecular structure during lignite pyrolysis

Understanding the mechanisms governing coal pyrolysis reactions, particularly in relation to the coal macromolecular structure, is crucial for improving energy efficiency and facilitating the transition of coal into a clean energy source. This study employs cutting-edge techniques, such as High-Resolution Transmission Electron Microscopy (HRTEM) and Thermogravimetric Analysis coupled with Fourier Transform Infrared Spectroscopy and Mass Spectrometry (TG–FTIR–MS), to analyze lignite and its residual solid samples subjected to pyrolysis across a range of temperatures from 300 °C to 1100 °C. The variational characteristics of the macromolecular structure during coal pyrolysis are examined. Utilizing molecular dynamics simulations, we analyze the evolution mechanism of the macromolecular carbon structure of organic matter during the coal pyrolysis process. The results show that the pyrolysis can be divided into three distinct phases: activation (30–300 °C), pyrolysis (300–650 °C), and condensation (650–1200 °C). During these phases, the coal structure undergoes complex transformations, including folding, twisting, shedding of small molecular side chains, and breaking of macromolecular side chains, ultimately leading to the directional arrangement of structural fragments. The structural units initially undergo decomposition, followed by growth and alignment in a certain direction. The spatial distribution of aromatic structural units evolves from local ordering to complete disordering, culminating in larger-scale, three-dimensional ordering. The order of bond breaking within the macromolecular structure of lignite pyrolysis is: oxygen-containing functional groups (such as C–O and COOH) > aliphatic structure (N–C and C–C) > aromatic structure (CC). By uncovering the reaction intermediates and pathways involved in lignite pyrolysis, this research provides a comprehensive quantitative description of the coal pyrolysis process. These insights offer invaluable theoretical support for the industrial-scale pyrolysis of coal, paving the way for more efficient and sustainable utilization of this crucial energy resource.

Design, Synthesis, and Theoretical Studies on the Benzoxadiazole and Thienopyrrole Containing Conjugated Random Copolymers for Organic Solar Cell Applications.

In this study, six different donor-π-acceptor1-π-donor-acceptor2 type random co-polymers containing benzodithiophene as a donor, benzooxadiazole (BO), and thieno[3,4-c]pyrrole-4,6-dione (TPD) as acceptor, have been synthesized and characterized. In addition to the acceptor core ratio at different values, the effect of aromatic bridge structures on the optical, electronic, and photovoltaic properties of six different random co-polymers is investigated by using thiophene and selenophene structures as aromatic bridge units. To investigate how the acceptor unit ratio and replacement of aromatic bridge units impact the structural, electronic, and optical properties of the polymers, density functional theory (DFT) calculations are carried out for the tetramer models. The open-circuit voltage (VOC), which is strongly correlated with the HOMO levels of the donor material, is enhanced with the increasing ratio of the TPD moiety. On the other hand, the short-circuit current (JSC), which is associated with the absorption ability of the donor material, is improved by the increasing ratio of BO moiety with the π-bridges. BO moiety dominant selenophene π-bridged co-polymer (P4) showed the best performance with a power conversion efficiency (PCE) of 6.26%, a JSC of 11.44mAcm2, a VOC of 0.80V, and a fill factor (FF) of 68.81%.

Stereoelectrochemistry of Tetranitrocalix[4]arenes

The present article reveals the differences in voltammetric reduction curves of isomeric nitrocalix[4]arenes (a kind of their “fingerprints”). This observation represents a contribution to a newly introduced utilization of electrochemical approach called “stereoelectro­chemistry” and extends the knowledge on these polycyclic molecules. In stereoelectrochemistry, the electrochemical data (potentials and their shifts, number of individual redox steps, proportions of their currents, reversibility etc.) in correlation with a series of derivatives can offer important information concerning the shape, geometry, conformation and static/dynamic behaviour of studied molecules in solution. Four possible atropoisomers of para-tetranitrocalix[4]arene were investigated by DC polarography and cyclic voltammetry in aprotic media (anhydrous N,N-dimethylformamide). Under such conditions, a typical reduction mechanism of a nitro compound involves a reversible single electron reduction step yielding an anion radical, followed by three-electron irreversible process assisted by protons (from moisture traces). While the already published most symmetric cone-conformer accepts first four electrons in two separated steps (which is in accordance with the “pinched” C2v shape of the molecule), the same behaviour was observed also in the case of 1,3-alt-derivative, the equilibrium geometry of which was predicted to be highly symmetric (S4), with no distinction among the nitro substituents. Hence, the 1,3-alt-molecule must oscillate around the equilibrium geometry (slower than the time scale of electron transfer) to produce a pinched limiting geometry with two different pairs of nitro groups (distal and proximal). The paco-derivative (and also its dinitro analogue) is reduced in three steps, during which the “tilted” aromatic unit is reduced first, followed by the opposite one (distal), and eventually another pair of proximal nitro groups (equivalent) is reduced simultaneously. The least symmetric 1,2-alt-compound (C1) is reduced in four single-electron, difficultly resolved steps due to small differences in the individual nitro groups energy.

Tuning a Cr-Catalyzed Ethylene Oligomerization Product Profile via a Rational Design of the N-aryl PNP Ligands

An approach towards incorporating varied degrees of steric profiles around the ligand’s backbone, which were envisaged to alter the catalytic paths leading to targeted 1-C8/1-C6 olefin products, were explored. Cr-pre-catalysts designed with PNP ligands comprising a fused aryl moiety were delivered at a relatively higher C8 olefin selectivity (up to 74.6 wt% and C8/C6 of 3.4) when the N-connection to the aromatic unit was placed at the 2-position. A relatively higher C6 olefin selectivity (up to 33.7 wt% and C8/C6 of 1.9) was achieved with the PNP unit anchored at the 1- or 6-position. Based on detailed catalytic studies, we confirm the fact that by introducing a controlled degree of bulkiness on the N-site through a judicious selection of the N-aryl moiety of different sizes, the selectivity of the targeted olefin product could be tuned in a rational manner.

Aliphatic hyperbranched polyphosphate: a novel multicolor RTP material with AIE character.

Long-lived photoluminescent probes are emerging as significant luminogens for biological imaging. However, currently, most long-lived luminescent materials contain expensive rare elements or cytotoxic bulky aromatic or conjugated units. Herein, a novel hyperbranched polyphosphate (HBPPE) was synthesized using triethyl phosphate (TEP) and ethylene glycol (EG) through a transesterification polycondensation reaction. The obtained HBPPE P1 can emit bright blue photoluminescence under UV light and show significant AIE character. Interestingly, the average photoluminescence lifetime of P1 is 12.82 μs. This suggests the first phosphorescent material without rare elements or aromatic structures attributed to the covalent-crystal-like structure. Besides, P1 shows an obvious red-shift along with the excitation wavelength, which emits blue, cyan, green, yellow and red photoluminescence, covering nearly all the visible light region. This study not only enriches the species of nonconventional multicolor AIE luminogens but also provides a concise method for the synthesis of HBPPE and demonstrates the possibility for phosphorescent materials without rare elements or bulky aromatic units.

Unit-Emitting Carbon Dots.

Understanding the photoluminescence mechanisms of carbon dots (C-dots) is of importance for both fundamental science and their corresponding applications. In this study, we verify the emitting-unit model of C-dots by an upgraded "contrastive analysis" research paradigm. Employing preparative thin-layer chromatography, we recently developed polyamide column chromatography separation techniques, and four kinds of highly correlative C-dots are obtained from a homologous sample made from ortho-aminophenol precursors. Combining comprehensive experimental characterizations, especially the direct evidence from electrospray ionization mass spectrometry, we demonstrate that the photoluminescence of the four C-dots comes from the same polycyclic aromatic hydrocarbon units (named as emitting units) indeed, although these C-dots have substantially different chemical compositions.

Click estradiol dimers with novel aromatic bridging units: synthesis and anticancer evaluation

Estradiol dimers (EDs) possess significant anticancer activity by targeting tubulin dynamics. In this study, we synthesised 12 EDs variants via copper-catalysed azide-alkyne cycloaddition (CuAAC) reaction, focusing on structural modifications within the aromatic bridge connecting two estradiol moieties. In vitro testing of these EDs revealed a marked improvement in selectivity towards cancerous cells, particularly for ED1–8. The most active compounds, ED3 (IC50 = 0.38 μM in CCRF-CEM) and ED5 (IC50 = 0.71 μM in CCRF-CEM) demonstrated cytotoxic effects superior to 2-methoxyestradiol (IC50 = 1.61 μM in CCRF-CEM) and exhibited anti-angiogenic properties in an endothelial cell tube-formation model. Cell-based experiments and in vitro assays revealed that EDs interfere with mitotic spindle assembly. Additionally, we proposed an in silico model illustrating the probable binding modes of ED3 and ED5, suggesting that dimers with a simple linker and a single substituent on the aromatic central ring possess enhanced characteristics compared to more complex dimers.

Palladium‐Catalyzed Direct C(sp3)−H Arylation of 5H‐Imidazo[2,1‐a]isoindole Scaffolds With Arylbromides

AbstractThe study of Pd(0)‐catalyzed C−H bond arylation of methyl 5H‐imidazo[2,1‐a]isoindole‐3‐carboxylates with aryl bromides is reported. This methodology gives ready access to a wide range of methyl 5H‐imidazo[2,1‐a]isoindole‐3‐carboxylates that are monoarylated at their benzylic sites. The C(sp3)−H bond arylation methodology is driven by regioselectivity under weakly basic conditions avoiding remarkably side C(sp2)−H poly‐arylation of the (hetero)aromatic unit. The process was applied to the preparation of novel imidazo[2,1‐a]isoindole‐based neurotransmitter Neuropeptide S antagonist analog.

One-Step Catalyst-Transfer Macrocyclization: Expanding the Chemical Space of Azaparacyclophanes.

In this paper, we report on a one-step catalyst-transfer macrocyclization (CTM) reaction, based on the Pd-catalyzed Buchwald-Hartwig cross-coupling reaction, selectively affording only cyclic structures. This route offers a versatile and efficient approach to synthesize aza[1n]paracyclophanes (APCs) featuring diverse functionalities and lumens. The method operates at mild reaction temperatures (40 °C) and short reaction times (∼2 h), delivering excellent isolated yields (>75% macrocycles) and up to 30% of a 6-membered cyclophane, all under nonhigh-dilution concentrations (35-350 mM). Structural insights into APCs reveal variations in product distribution based on different endocyclic substituents, with steric properties of exocyclic substituents having minimal influence on the macrocyclization. Aryl-type endocyclic substituents predominantly yield 6-membered macrocycles, while polycyclic aromatic units such as fluorene and carbazole favor 4-membered species. Experimental and computational studies support a proposed mechanism of ring-walking catalyst transfer that promotes the macrocycle formation. It has been found that the macrocyclization is driven by the formation of cyclic conformers during the oligomerization step favoring an intramolecular C-N bond formation that, depending on the cycle size, hinges on either preorganization effect or kinetic increase of the reductive elimination step or a combination of the two. The CTM process exhibits a "living" behavior, facilitating sequential synthesis of other macrocycles by introducing relevant monomers, thus providing a practical synthetic platform for chemical libraries. Notably, CTM operates both under diluted and concentrated regimes, offering scalability potential, unlike typical macrocyclization reactions usually operating in the 0.1-1 mM range.

Heterocycle- and Amine-Free Electrochromic and Electrofluorochromic Molecules for Energy-Saving See-Through Smart Windows and Displays.

Electrochromic (EC) smart windows are an elegant alternative to dusty curtains, blinds, and traditional dimming devices. The EC energy storage smart windows and displays received remarkable attention in the optoelectronic industry as they hold promise for high energy efficiency, low power consumption, reversibility, and swift response to stimuli. However, achieving these properties remains challenging. Moreover, most EC molecules do not exhibit electrofluorochromism, which is highly essential for smart displays because its EC property can modulate the solar heat entering the building, and its electrofluorochromic (EFC) aspects can create lighting during the night. In this work, a structure-property relationship is utilized to develop new electrochromes that can store the injected charge, and these molecules indeed exhibit electrofluorochromism. The compounds are synthesized from tetrabenzofluorene with two aromatic acceptor units, and avoids the use of widely studied heterocycles and amine derivatives. The electrochromes switches from yellow to dark hue in solution, solid, and gel state. The compounds display exceptional electrochemical stability and reversibility in 1000 cycles and capacity retention of 93-100 % in 300 charging-discharging cycles. The proof-of-concept device fabrication of the self-dimming EC smart window presented here demonstrates that it can furnish visual comfort, modulate transmitted light and glare, and reduce energy usage.

Adamantylated Calix[4]arenes Bearing CuAAC-Ready 2-Azidoethyl or Propargyl Functionalities

1,3-Alternate calix[4]arenes were prepared, having bulky adamantyl groups in the p-positions of all four aromatic units of the macrocycles and pairs of propargyl or 2-azidoethyl groups alternating with n-propyl groups at the phenol oxygen atoms. The step-wise syntheses were carried out through a selective distal alkylation of the parent p-adamantylcalix[4]arene with propargyl bromide or 1,2-dibromoethane, resulting in calix[4]arenes bearing pairs of propargyl or 2-bromoethyl groups at their narrow rims. The bromine atoms were replaced by azide groups, and then both calix[4]arene diethers were exhaustively alkylated at the remaining OH-groups with 1-iodopropane under stereoselective conditions to fix the macrocycles in an 1,3-alternate shape. The structures of the prepared p-adamantylcalix[4]arenes were confirmed by NMR and HRMS data, and, for the 1,3-alternate dipropargyl ether, the X-ray diffraction data were also collected. Preliminary data on the reactivity of the prepared calixarenes under the CuAAC conditions suggested a strong steric hampering created by the adamantane units nearby the reacting alkyne or azide groups that affected the outcome of the two-fold cycloaddition involving the calixarene bis(azides) or bis(alkynes) as complementary partners.

Surface assisted laser desorption/ionization mass spectrometry of lithium cationized lignans – A tool for rapid screening of plant extracts

Lignans are one of the most widespread classes of plant secondary metabolites possessing unique biological activities. The search for new sources of such compounds, their screening and identification in plant biomass is an urgent task, requiring the use of advanced analytical methods. In the present study, matrix-free surface assisted laser desorption/ionization (SALDI) mass spectrometry was proposed for its solution. The combination of carbon nanocoating sputtered on a target plate with lithium cationization allowed obtaining high-quality mass spectra of eight coniferous wood lignans with different bonds between aromatic units (secoisolariciresinol, matairesinol, 7-hydroxymatairesinol, nortrachelogenin, pinoresinol, guaiacylglycerol-β-guaiacyl ether, dehydrodihydrodiisoeugenol, and divanillin). Three types of fragmentation methods (post-source decay, high- and low-energy collision induced dissociation) for the first time were implemented on two types of MALDI instruments. Regardless of tandem mass spectrometry technique, lignans demonstrated the similar fragmentation patterns including the cleavage of bonds between aromatic units with the formation of mostly lithiated product ions. The low-energy collision induced dissociation in quadrupole ion trap provided the most informative tandem mass spectra and multi-stage fragmentation capabilities in structural studies. On this basis, an approach to rapid, high-throughput, and low-cost screening and tentative identification of lignans including isomeric compounds in plant biomass was developed and successfully tested on real samples of pine, fir, spruce, and larch knotwood extracts.

Structure and Chiroptical Properties of Anthra[1,2-a]anthracene-1-yl Dimers as New Biaryls.

Dimers of anthra[1,2-a]anthracene-1-yl units and its mesityl derivative were synthesized by Ni(0)-mediated coupling of the corresponding chloro derivatives as new biaryls. The X-ray analysis and DFT calculations revealed that two polycyclic aromatic units with nonplanar deformations took a twisted conformation about the single bond as a chiral axis. Enantiomers of the nonsubstituted compound were resolved by chiral HPLC, and the enantiopure samples showed intense Cotton effects at 321 nm in the circular dichroism (CD) spectra and emission bands at 449 nm in the circularly polarized luminescence (CPL) spectra with dissymmetry factor of |glum| 3.6×10-3. The absolute stereochemistry of this biaryl was determined by the theoretical calculation of CD spectrum by the time-dependent DFT method. The barrier to enantiomerization was determined to be 108 kJ mol-1 at 298 K. The dynamic process proceeded via a stepwise mechanism involving the helical inversion of each aromatic unit and the rotation about the biaryl axis as analyzed by the DFT calculations.

Poly(butylene oxalate-co-terephthalate): A PBAT-like but rapid hydrolytic degradation plastic

Concerns over worldwide plastic pollution have led to the development of biodegradable polyester materials with excellent physical and chemical properties through the copolymerization of poly(butylene oxalate) (PBOx). As a result, poly(butylene oxalate-co-terephthalate)s (PBOTs) with varying compositions, were prepared by incorporating aromatic units. Studies have indicated that PBOT-47 (with a 47% molar terephthalate), exhibits exceptional mechanical properties. With an elongation at break of 1160% and a tensile strength that remains above 30 MPa, similar to or even better than those of the commercial biodegradable plastic poly(butylene adipate-co-terephthalate) PBAT-47 (47% molar terephthalate). Moreover, the permeability coefficients of PBAT-47 for H2O, CO2 and O2 were 5.8, 50.6 and 5.6 times higher than that of PBOT-47, revealing the superior barrier properties of PBOT. Through experimental research and theoretical simulation, the mechanism of the copolymer hydrolysis was elucidated. The readily hydrolytic nature of the oxalate unit endows it with the capacity for rapid degradation, possessing the potential to be a short-term degradable material with physical properties similar to PBAT.

Thermodynamically Stable Functionalization of Microporous Aromatic Frameworks with Sulfonic Acid Groups by Inserting Methylene Spacers.

Porous aromatic frameworks (PAFs) are an auspicious class of materials that allow for the introduction of sulfonic acid groups at the aromatic core units by post-synthetic modification. This makes PAFs promising for proton-exchange materials. However, the limited thermal stability of sulfonic acid groups attached to aromatic cores prevents high-temperature applications. Here, we present a framework based on PAF-303 where the acid groups were added as methylene sulfonic acid side chains in a two-step post-synthetic route (SMPAF-303) via the intermediate chloromethylene PAF (ClMPAF-303). Elemental analysis, NMR spectroscopy, electrochemical impedance spectroscopy and X-ray photoelectron spectroscopy were used to characterize both frameworks and corroborate the successful attachment of the side chains. The resulting framework SMPAF-303 features high thermal stability and an ion-exchange capacity of about 1.7 mequiv g-1. The proton conductivity depends strongly on the adsorbed water level. It reaches from about 10-7 S cm-1 for 33% RH to about 10-1 S cm-1 for 100% RH. We attribute the strong change to a locally alternating polarity of the inner surfaces. The latter introduces bottleneck effects for the water molecule and oxonium ion diffusion at lower relative humidities, due to electrolyte clustering. When the pores are completely filled with water, these bottlenecks vanish, leading to an unhindered electrolyte diffusion through the framework, explaining the conductivity rise.

Synchronous Regulation of Donor and Acceptor Microstructure using Thiophene‐Derived Non‐Halogenated Solvent Additives for Efficient and Stable Organic Solar Cells

AbstractSolvent additives are pivotal for enhancing the morphology, efficiency, and stability of organic solar cells (OSCs). However, the widely used additive, 1,8‐diiodooctane (DIO), has drawbacks like harmful halogen content and potential OSC degradation. To address these issues, novel non‐halogenated, thienyl‐alkyl‐thienyl structural solvent additives—DTP, DTH, and DTN—featuring varying alkyl linker lengths of (CH2)3, (CH2)6, and (CH2)9, respectively are introduced. Additives with longer alkyl linkers, DTH and DTN, effectively dissolve and strongly interact with both the donor polymer PM6 and acceptor L8‐BO. This dual interaction enables precise tuning of their microstructures, resulting in enhanced crystallinity. Upon incorporating DTH as an additive in OSCs (PM6:L8‐BO), a minimal voltage loss is observed, leading to an impressive efficiency of 18.51%, surpassing the 17.90% achieved with DIO. Furthermore, DTH‐based devices demonstrated superior photostability. In a ternary blend system (PM6:D18‐Cl:L8‐BO), an efficiency of 19.07% is attained, outperforming previous non‐halogenated solvent additive‐based OSCs. Furthermore, employing a non‐halogenated processing solvent combination of toluene and carbon disulfide, a high PCE of 18.82% is achieved. These results underscore the efficacy of designing solvent additives with aromatic and alkyl units, enabling tailored interactions with the donor and acceptor, thereby presenting a robust strategy for optimizing OSC performance and stability.

Transient-State Self-Bipolarized Organic Frameworks of Single Aromatic Units for Natural Sunlight-Driven Photosynthesis of H2O2.

Constructing π-conjugated polymer structures through covalent bonds dominates the design of organic framework photocatalysts, which significantly depends on the selection of multiple donor-acceptor building blocks to narrow the optical gap and increase the lifetimes of charge carriers. In this work, self-bipolarized organic frameworks of single aromatic units are demonstrated as novel broad-spectrum-responsive photocatalysts for H2O2 production. The preparation of such photocatalysts is only to fix the aromatic units (such as 1,3,5-triphenylbenzene) with alkane linkers in 3D space. Self-bipolarized aromatic units can drive the H2O2 production from H2O and O2 under natural sunlight, wide pH ranges (3.0-10.0) and natural water sources. Moreover, it can be extended to catalyze the oxidative coupling of amines. Experimental and theoretical investigation demonstrate that such a strategy obeys the mechanism of through-space π-conjugation, where the closely face-to-face overlapped aromatic rings permit the electron and energy transfer through the large-area delocalization of the electron cloud under visible light irradiation. This work introduces a novel design concept for the development of organic photocatalysts, which will break the restriction of conventional through-band π-conjugation structure and will open a new way in the synthesis of organic photocatalysts.