Molecularly Woven Cationic Covalent Organic Frameworks for Highly Selective Electrocatalytic Conversion of CO2 to CO.

Coupling carbon capture with electrocatalytic carbon dioxide reduction (CO2R) to yield high-value chemicals presents an appealing avenue for combating climate change, yet achieving highly selective electrocatalysts remains a significant challenge. Herein, two molecularly woven covalent organic frameworks (COFs) are designed, namely CuCOF and CuCOF+, with copper(I)-bisphenanthroline complexes as building blocks. The metal-organic helical structure unit made the CuCOF and CuCOF+ present woven patterns, and their ordered pore structures and cationic properties enhanced their CO2 adsorption and good conductivity, which is confirmed by gas adsorption and electrochemical analysis. In the electrocatalytic CO2R measurements, CuCOF+ decorated with extra ethyl groups exhibit a main CO product with selectivity of 57.81%, outperforming the CuCOF with 42.92% CO at the same applied potential of 0.8 VRHE. After loading Pd nanoparticles, CuCOF-Pd and CuCOF+-Pd performed increased CO selectivity up to 84.97% and 95.45%, respectively. Combining the DFT theoretical calculations and experimental measurements, it is assumed that the molecularly woven cationic COF provides a catalytic microenvironment for CO2R and ensures efficient charge transfer from the electrode to the catalytic center, thereby achieving high electrocatalytic activity and selectivity. The present work significantly advances the practice of cationic COFs in real-time CO2 capture and highly selective conversion to value-added chemicals.

Unlocking Fe(III) Ions Improving Oxygen Evolution Reaction Activity and Dynamic Stability of Anodized Nickel Foam.

Fe has been reported to play a crucial role in improving the catalytic activity and stability of Ni/Co-based electrocatalysts for the oxygen evolution reaction (OER), while the Fe effect remains intangible. Here, we design several experiments to identify the activity and stability improvement using porous anodized nickel foam (ANF) as the electrode and 1.0 M KOH containing 1000 µM Fe(III) ions as the electrolyte. Systematic investigations reveal that Ni sites serve as hosts to capture Fe ions to create active FeNi-based intermediates on the surface of ANF to improve the OER activity significantly, and Fe ions regulate catalytic equilibrium and maintain the stability for a long time. The system exhibits 242 and 343 mV overpotentials to reach 10 and 1000 mA cm-2 current densities and a robust stability of 360 h at an industrially suitable current density (1000 mA cm-2). This work expands insights into the Fe(III) catalysis effect on the OER efficiency of Ni-based catalysts and provides an economical and practical way to commercial application.

Silicon photocathode functionalized with osmium complex catalyst for selective catalytic conversion of CO2 to methane.

Solar-driven CO2 reduction to yield high-value chemicals presents an appealing avenue for combating climate change, yet achieving selective production of specific products remains a significant challenge. We showcase two osmium complexes, przpOs, and trzpOs, as CO2 reduction catalysts for selective CO2-to-methane conversion. Kinetically, the przpOs and trzpOs exhibit high CO2 reduction catalytic rate constants of 0.544 and 6.41 s-1, respectively. Under AM1.5 G irradiation, the optimal Si/TiO2/trzpOs have CH4 as the main product and >90% Faradaic efficiency, reaching -14.11 mA cm-2 photocurrent density at 0.0 VRHE. Density functional theory calculations reveal that the N atoms on the bipyrazole and triazole ligands effectively stabilize the CO2-adduct intermediates, which tend to be further hydrogenated to produce CH4, leading to their ultrahigh CO2-to-CH4 selectivity. These results are comparable to cutting-edge Si-based photocathodes for CO2 reduction, revealing a vast research potential in employing molecular catalysts for the photoelectrochemical conversion of CO2 to methane.

Stepwise Toward Pure Blue Organic Light-Emitting Diodes by Synergetically Locking and Shielding Carbonyl/Nitrogen-Based MR-TADF Emitters.

Deep-blue multi-resonance (MR) emitters with stable and narrow full-width-at-half-maximum (FWHM) are of great importance for widening the color gamut of organic light-emitting diodes (OLEDs). However, most planar MR emitters are vulnerable to intermolecular interactions from both the host and guest, causing spectral broadening and exciton quenching in thin films. Their emission in the solid state is environmentally sensitive, and the color purity is often inferior to that in solutions. Herein, a molecular design strategy is presented that simultaneously narrows the FWHM and suppresses intermolecular interactions by combining intramolecular locking and peripheral shielding within a carbonyl/nitrogen-based MR core. Intramolecularly locking carbonyl/nitrogen-based bears narrower emission of 2,10-dimethyl-12,12-diphenyl-4H-benzo[9,1]quinolizino[3,4,5,6,7-defg]acridine-4,8(12H)-dione in solution and further with peripheral-shielding groups, deep-blue emitter (12,12-diphenyl-2,10-bis(9-phenyl-9H-fluoren-9-yl)-4H-benzo[9,1]quinolizino[3,4,5,6,7-defg]acridine-4,8(12H)-dione, DPQAO-F) exhibits ultra-pure emission with narrow FWHM (c.a., 24 nm) with minimal variations (∆FWHM ≤ 3 nm) from solution to thin films over a wide doping range. An OLED based on DPQAO-F presents a maximum external quantum efficiency (EQEmax) of 19.9% and color index of (0.134, 0.118). Furthermore, the hyper-device of DPQAO-F exhibits a record-high EQEmax of 32.7% in the deep-blue region, representing the first example of carbonyl/nitrogen-based OLED that can concurrently achieve narrow bandwidth in the deep-blue region and a high electroluminescent efficiency surpassing 30%.

Thiyl Radical Trapped by Cobalt Catalysis: An Approach to Markovnikov Thiol-Ene Reaction.

In the presence of a thiyl radical species, the catalytic Markovnikov thiol-ene reaction is challenging because it prefers to proceed via a radical pathway, thereby leading to anti-Markovnikov selectivity. In this work, a rare example of thiyl radical engaged in Markovnikov thiol-ene reaction enabled by cobalt catalysis is reported. This protocol features the avoidance of unique oxidants, exclusive regioselectivity, and broad substrate scope. Scalable synthesis and late-stage modification of complex molecules demonstrate the practicability of the protocol.

Molecular Engineering of Perylene Diimide Polymers with a Robust Built-in Electric Field for Enhanced Solar-Driven Water Splitting.

The built-in electric field of the polymer semiconductors could be regulated by the dipole moment of its building blocks, thereby promoting the separation of photogenerated carriers and achieving efficient solar-driven water splitting. Herein, three perylene diimide (PDI) polymers, namely oPDI, mPDI and pPDI, are synthesized with different phenylenediamine linkers. Notably, the energy level structure, light-harvesting efficiency, and photogenerated carrier separation and migration of polymers are regulated by the orientation of PDI unit. Among them, oPDI enables a large dipole moment and robust built-in electric field, resulting in enhanced solar-driven water splitting performance. Under simulated sunlight irradiation, oPDI exhibits the highest photocurrent of 115.1 µA cm-2 for photoelectrochemical oxygen evolution, which is 11.5 times that of mPDI, 26.8 times that of pPDI and 104.6 times that of its counterparts PDI monomer at the same conditions. This work provides a strategy for designing polymers by regulating the orientation of structural units to construct efficient solar energy conversion systems.

Nitrogen-doped carbon dots for efficient deep-blue light-emitting diodes with CIE closely approaching the HDTV standard color Rec.BT.709.

Here, we demonstrate deep-blue carbon dots (CDs) with luminescence centered at 415 nm and PLQY exceeding 60% via nitrogen doping. A bright and high-color-purity CDs-based light-emitting diode (CLED) is achieved with an external quantum efficiency (EQE) of 1.74%, a maximum luminance of 1155.0 cd m-2, and a colour coordinate (0.16, 0.08) closely approaching the HDTV standard color Rec.BT.709 (0.15, 0.06) specification.

Interface-Engineered Ni-Coated CdTe Heterojunction Photocathode for Enhanced Photoelectrochemical Hydrogen Evolution.

Photoelectrochemical (PEC) water splitting for hydrogen production using the CdTe photocathode has attracted much interest due to its excellent sunlight absorption property and energy band structure. This work presents a study of engineered interfacial energetics of CdTe photocathodes by deposition of CdS, TiO2, and Ni layers. A heterostructure CdTe/CdS/TiO2/Ni photocathode was fabricated by depositing a 100-nm n-type CdS layer on a p-type CdTe surface, with 50 nm TiO2 as a protective layer and a 10 nm Ni layer as a co-catalyst. The CdTe/CdS/TiO2/Ni photocathode exhibits a high photocurrent density (Jph) of 8.16 mA/cm2 at 0 V versus reversible hydrogen electrode (VRHE) and a positive-shifted onset potential (Eonset) of 0.70 VRHE for PEC hydrogen evolution under 100 mW/cm2 AM1.5G illumination. We further demonstrate that the CdTe/CdS p-n junction promotes the separation of photogenerated carriers, the TiO2 layer protects the electrode from corrosion, and the Ni catalyst improves the charge transfer across the electrode/electrolyte interface. This work provides new insights for designing noble metal-free photocathodes toward solar hydrogen development.

Minisci reaction of heteroarenes and unactivated C(sp3)-H alkanes via a photogenerated chlorine radical.

Here, an efficient Minisci reaction of heteroarenes and unactivated C(sp3)-H alkanes was achieved using an inexpensive FeCl3 as a photocatalyst. The photogenerated chlorine radical contributed to the HAT of C-H and subsequently initiated this reaction. Surprisingly, salt water and even seawater can act as a chlorine radical source, which provided an enlightening idea for future organic synthesis methods.

Enhanced Photoelectrochemical Water Splitting of Black Silicon Photoanode with pH-Dependent Copper-Bipyridine Catalysts.

Since the water oxidation half-reaction requires the transfer of multi-electrons and the formation of O-O bond, it's crucial to investigate the catalytic behaviours of semiconductor photoanodes. In this work, a bio-inspired copper-bipyridine catalyst of Cu(dcbpy) is decorated on the nanoporous Si photoanode (black Si, b-Si). Under AM1.5G illumination, the b-Si/Cu(dcbpy) photoanode exhibits a high photocurrent density of 6.31 mA cm-2 at 1.5 VRHE at pH 11.0, which is dramatically improved from the b-Si photoanode (1.03 mA cm-2 ) and f-Si photoanode (0.0087 mA cm-2 ). Mechanism studies demonstrate that b-Si/Cu(dcbpy) has improved light-harvesting, interfacial charge-transfer, and surface area for water splitting. More interestingly, b-Si/Cu(dcbpy) exhibits a pH-dependent water oxidation behaviour with a minimum Tafel slope of 241 mV/dec and the lowest overpotential of 0.19 V at pH 11.0, which is due to the monomer/dimer equilibrium of copper catalyst. At pH ∼11, the formation of dimeric hydroxyl-complex could form O-O bond through a redox isomerization (RI) mechanism, which decreases the required potential for water oxidation. This in-depth understanding of pH-dependent water oxidation catalyst brings insights into the design of dimer water oxidation catalysts and efficient photoanodes for solar energy conversion.

Regulable cross-coupling of alcohols and benzothiazoles via a noble-metal-free photocatalyst under visible light.

Here, we realize a regulable cross-coupling reaction using alcohols as alkylating reagents to functionalize benzothiazoles. Two types of cross-coupling products are obtained with the highest isolated yields of up to 99% and 90% for alkyl- and acetyl-derived benzothiazoles, respectively, which opens up a broad research prospect for expanding alcohols as alkylating reagents.

Deep-Blue OLEDs with Rec.2020 Blue Gamut Compliance and EQE Over 22% Achieved by Conformation Engineering.

To achieve high-efficiency deep-blue electroluminescence satisfying Rec.2020 standard blue gamut, two thermally activated delayed fluorescent (TADF) emitters are developed: 5-(2,12-di-tert-butyl-5,9-dioxa-13b-boranaphtho[3,2,1-de]anthracen-7-yl)-10,10-diphenyl-5,10-dihydrodibenzo[b,e][1,4]azasiline (TDBA-PAS) and 10-(2,12-di-tert-butyl-5,9-dioxa-13b-boranaphtho[3,2,1-de]anthracen-7-yl)-9,9-diphenyl-9,10-dihydroacridine (TDBA-DPAC). Inheriting from their parented organoboron multi-resonance core, both emitters show very promising deep-blue emissions with relatively narrow full width at half-maximum (FWHM, ≈50 nm in solution), high photoluminescence quantum yield (up to 92.3%), and short emission lifetime (≤2.49 µs) with fast reverse intersystem crossing (>106 s-1 ) in doped films. More importantly, replacing the spiro-centered sp3 C atom (TDBA-DPAC) with the larger-radius sp3 Si atom (TDBA-PAS), enhanced conformational heterogeneities in bulky-group-shielded TADF molecules are observed in solution, doped film, and device. Consequently, OLEDs based on TDBA-PAS retain high maximum external quantum efficiencies ≈20% with suppressed efficiency roll-off and color index close to Rec.2020 blue gamut over a wide doping range of 10-50 wt%. This study highlights a new strategy to restrain spectral broadening and redshifting and efficiency roll-off in the design of deep-blue TADF emitters.

Recent Advances in Visible-Light Photoredox Catalysis for the Thiol-Ene/Yne Reactions.

Visible-light photoredox catalysis has been established as a popular and powerful tool for organic transformations owing to its inherent characterization of environmental friendliness and sustainability in the past decades. The thiol-ene/yne reactions, the direct hydrothiolation of alkenes/alkynes with thiols, represents one of the most efficient and atom-economic approaches for the carbon-sulfur bonds construction. In traditional methodologies, harsh conditions such as stoichiometric reagents or a specialized UV photo-apparatus were necessary suffering from various disadvantages. In particular, visible-light photoredox catalysis has also been demonstrated to be a greener and milder protocol for the thiol-ene/yne reactions in recent years. Additionally, unprecedented advancements have been achieved in this area during the past decade. In this review, we will summarize the recent advances in visible-light photoredox catalyzed thiol-ene/yne reactions from 2015 to 2021. Synthetic strategies, substrate scope, and proposed reaction pathways are mainly discussed.

Carbon Dots/α-Fe2O3-Fe3O4 nanocomposite: Efficient synthesis and application as a novel electrochemical aptasensor for the ultrasensitive determination of aflatoxin B1.

Developing an effective method for the detection of aflatoxin B1 (AFB1) remains an arduous task due to the high toxicity of AFB1 to a health concern. In this study, a sensitive and reliable electrochemical aptasensor based on carbon dots/α-Fe2O3-Fe3O4 nanocomposite (CDs/α-Fe2O3-Fe3O4) is constructed for the determination of AFB1. The CDs have good electrical conductivity and large specific surface areas to improve the aptasensor's sensitivity. The α-Fe2O3-Fe3O4 can not only improve the catalytic performance of the aptasensor but also have magnetism, which can realize the recovery of CDs/α-Fe2O3-Fe3O4 to avoid material waste and environmental pollution. This electrochemical aptasensor can achieve a good linear (0.001-100.0 nM) and excellent detection limit (0.5 pM) for the determination of AFB1. In addition, the aptasensor was also applied to determine AFB1 in beer, rice, and peanuts, all results were in good agreement with HPLC, indicating that the electrochemical aptasensor has a broad application prospect.

Photoinduced Radical Cascade Cyclization: A Metal-Free Approach to Access Difluoroalkylated Dioxodibenzothiazepines.

A simple and mild photoredox catalytic approach to access difluoroalkylated dioxodibenzothiazepines in high regioselectivity via radical cascade cyclization has been described herein. In contrast to previous methods, this strategy does not involve the use of transition-metal catalysts and avoids the potential disadvantages of inevitable toxicity and the tedious removal process of metal catalysts. The commercially available and inexpensive CF2 precursors, wide substrate scope, and mild reaction conditions demonstrate the practicability of this approach.

Constructing Highly Efficient Blue OLEDs with External Quantum Efficiencies up to 7.5 % Based on Anthracene Derivatives.

Acquiring desirable device performance with deep-blue color purity that fulfills practical application requirements is still a challenge. Bipolar fluorescent emitters with hybrid local and charge transfer (HLCT) state may serve to address this issue. Herein, by inserting anthracene core in the deep-blue building blocks, the authors successfully developed two highly twisted D-π-A fluorescent emitters, ICz-An-PPI and IP-An-PPI, featuring different acceptor groups. Both exhibited superb thermal stabilities, high photo luminescent quantum yields and excellent bipolar transport capabilities. The non-doped OLEDs using ICz-An-PPI and IP-An-PPI as the emitting layers showed efficient blue emission with an external quantum efficiency (EQEmax ) of 4.32 % and 5.41 %, and the CIE coordinates of (0.147, 0.180) and (0.149, 0.150), respectively. In addition, the deep blue doped device based on ICz-An-PPI was achieved with an excellent CEmax of 5.83 cd A-1 , EQEmax of 4.6 % and the CIE coordinate of (0.148, 0.078), which is extremely close to the National Television Standards Committee (NTSC) standard. Particularly, IP-An-PPI-based doped device had better performance, with an EQEmax of 7.51 % and the CIE coordinate of (0.150, 0.118), which was very impressive among the recently reported deep-blue OLEDs with the CIEy <0.12. Such high performance may be attributed to the hot exciton HLCT mechanism via T7 to S2 . Our work may provide a new approach for designing high-efficiency deep-blue materials.

Photoredox/cobaloxime co-catalyzed allylation of amines and sulfonyl hydrazines with olefins to access α-allylic amines and allylic sulfones.

Herein, we reported a dual-catalytic platform for the allylation of amines and sulfonyl hydrazines with olefins to selectively access α-allylic amines and allylic sulfones in good yields by combining photoredox catalysis and cobaloxime catalysis. This strategy avoided the use of a stoichiometric amount of terminal oxidant and the use of pre-functionalized allylic precursors, representing a green and ideal atom- & step-economical process. Good substrate scope and gram-scale synthesis demonstrated the utility of this protocol. Mechanistic studies revealed that a radical process is probably involved in this reaction.

Light-Promoted and Tertiary-Amine-Assisted Hydroxysulfenylation of Alkenes: Selective and Direct One-Pot Synthesis of ß-Hydroxysulfides.

A light-promoted and tertiary-amine-assisted strategy for efficient hydroxysulfenylation of both electron-rich and electron-deficient alkenes with thiophenols to selectively and directly access ß-hydroxysulfides in one pot is described herein. In contrast to the previously reported thiol-oxygen co-oxidation reactions, this simple and sustainable approach features mild reaction conditions, high efficiency, and excellent functional group tolerance.

Multifunctional Materials Serving as Efficient Non-Doped Violet-Blue Emitters and Host Materials for Phosphorescence.

Efficient multifunctional materials acting as violet-blue emitters, as well as host materials for phosphorescent OLEDs, are crucial but rare due to demand that they should have high first singlet state (S1 ) energy and first triplet state (T1 ) energy simultaneously. In this study, two new violet-blue bipolar fluorophores, TPA-PI-SBF and SBF-PI-SBF, were designed and synthesized by introducing the hole transporting moiety triphenylamine (TPA) and spirobifluorene (SBF) unit that has high T1 into high deep blue emission quantum yield group phenanthroimidazole (PI). As the results, the non-doped OLEDs based on TPA-PI-SBF exhibited excellent EL performance with a maximum external quantum efficiency (EQEmax ) of 6.76 % and a violet-blue emission with Commission Internationale de L'Eclairage (CIE) of (0.152, 0.059). The device based on SBF-PI-SBF displayed EQEmax of 6.19 % with CIE of (0.159, 0.049), which nearly matches the CIE coordinates of the violet-blue emitters standard of (0.131, 0.046). These EL performances are comparable to the best reported non-doped deep or violet-blue emissive OLEDs with CIEy<0.06 in recent years. Additionally, the green, yellow and red phosphorescent OLEDs with TPA-PI-SBF and SBF-PI-SBF as host materials achieved a high EQEmax of about 20 % and low efficiency roll-off at the ultra-high luminance of 10 000 cd m-2 . These results provided a new construction strategy for designing high-performance violet-blue emitters, as well as efficient host materials for phosphorescent OLEDs.

Directing-Group-Assisted Markovnikov-Selective Hydrothiolation of Styrenes with Thiols by Photoredox/Cobalt Catalysis.

In contrast with the well-developed radical thiol-ene reaction to access anti-Markovnikov-type products, the research on the catalytic Markovnikov-selective hydrothiolation of alkenes is very restricted. Because of the catalyst poisoning of metal catalysts by organosulfur compounds, limited examples of transition-metal-catalyzed thiol-ene reactions have been reported. However, in this work, a directing-group-assisted hydrothiolation of styrenes with thiols by photoredox/cobalt catalysis is found to proceed smoothly to afford Markovnikov-type sulfides with excellent regioselectivity.