Engineering Spin States of Isolated Copper Species in a Metal-Organic Framework Improves Urea Electrosynthesis

The catalytic activities are generally believed to be relevant to the electronic states of their active center, but understanding this relationship is usually difficult. Here, we design two types of catalysts for electrocatalytic urea via a coordination strategy in a metal–organic frameworks: Cu^(Ⅲ)-HHTP and Cu^(Ⅱ)-HHTP. Cu^(Ⅲ)-HHTP exhibits an improved urea production rate of 7.78 mmol h^(−1)g^(−1) and an enhanced Faradaic efficiency of 23.09% at-0.6 V vs. reversible hydrogen electrode, in sharp contrast to Cu^(Ⅱ)-HHTP.Isolated CuⅢspecies with S = 0 spin ground state are demonstrated as the active center in Cu^(Ⅲ)-HHTP, different from Cu^(Ⅱ) with S = 1/2 in Cu^(Ⅱ)-HHTP. We further demonstrate that isolated Cu^(Ⅲ)with an empty dx2-y20orbital in Cu^(Ⅲ)-HHTP experiences a single-electron migration path with a lower energy barrier in the C–N coupling process, while Cu^(Ⅱ)with a single-spin state( d_(x2-y2)^(1)) in Cu^(Ⅱ)-HHTP undergoes a two-electron migration pathway.

Spontaneous Symmetry Breaking of Iridium and Ruthenium Metallophosphors for the Constructions of Chiral Light-Harvesting Systems

Symmetry breaking for chirality generation and lightharvesting for solar energy conversion are two momentous topics in natural systems.The construction of a chiral light-harvesting system completely based on symmetry breaking is a formidable challenge.Here,we report the spontaneous chiral symmetry breaking(CSB)of two iridium and ruthenium metallophosphors(IrD and RuA)with the assistance of achiral solvents.The subtle noncovalent intermolecular interactions between complexes and polar solvents play a vital role in the crystallization of homochiral molecules and the resulting CSB.Utilizing a molecular doping strategy,transferred,ampli-fied,and inverted circularly polarized luminescence(CPL)was achieved in the binary microcrystals(MCs)composed of chiral/achiral IrD and achiral/chiral RuA,with large dissymmetry factors(glum,up to 0.06)and enhanced emission quantum yields(over 35%).The use of only 0.05%of chiral RuA in the lattice of achiral IrD led to the chiral amplification with glum of 1×10−2 and morphology transition,while inverted and white CPL were obtained in MCs containing monodispersed chiral RuA in the lattice cavities of another polymorphic crystal of IrD.Diffuse reflection circular dichroism measurements gave information on the chirality transfer mechanisms behind these spin-related chiroptical properties.

Acceptor-Type Singlet Fission Material Based on Strong Absorption Tetracyanothienoquinoid Skeleton

The practical efficiency of singlet fission(SF)-based photovoltaic devices is still far from satisfactory due to the limited scope of SF materials suitable for device application and the scarcity of schemes available for triplet utilization.Most SF materials identi-fied to date are typically electron donors while acceptor-type SF materials remain largely unexplored.Basically,the combination of a conventional electron donor and SF-active electron acceptor could circumvent the competitive energy transfer channel and better play the unique advantages of the SF process,which might be an adequate alternative for practical application.In this work,we presented a new acceptor-type SF material based on a tetracyanothienoquinoid skeleton.Such a quinoid skeleton exhibited strong absorption,ultrafast SF process,and excellent stability.Using transient spectroscopy and multireference calculations(XDWCASPT2),the SF dynamics were examined featuring the rapid generation and subsequent annihilation and/or partial dissociation of multiexciton states.Therefore,our results not only provide a robust acceptor-type SF material but also suggest an adequate donor–acceptor alternative for SF-based solar cells,which could pave the way for the practical application of such a potential process.

Circularly polarized phosphorescence and photon transport of micro/nanocrystals of ruthenium and iridium complexes with chiral anions

Materials with efficient circularly polarized phosphorescences(CPPs) are of potential use in advanced data encryption and anticounterfeiting, bioimaging, optoelectronic devices and so forth. Herein, a simple method is presented for the preparations of CPP-active micro/nanocrystals with large luminescence dissymmetry factors(glum), high phosphorescence quantum efficiencies(Φ_(P)) and tunable emission colors. Diastereomeric Ir^(Ⅲ) and Ru^(Ⅱ) complexes with chiral(±)-camphorsulfonate counter-anions are readily synthesized and assembled into crystalline microrods, microplates or nanofibers with ordered morphologies. The chirality information of chiral counter-anions is efficiently transferred to the metal components to afford CPPs with cyan, green,yellow, or red emission colors and Φ_(P)in the range of 5%–85%. The number of chiral anions is found to play a role in influencing the CPP magnitudes of these crystals. The dicationic Ru^(Ⅱ) and tricationic Ir^(Ⅲ) complexes show glumvalues in the 10^(-2)order, which are much larger with respect to those of monocationic Ir^(Ⅲ) complexes. Single crystal X-ray analysis is performed to obtain information on the chirality transfer of these materials. In addition, circularly polarized photonic signal waveguiding is demonstrated using the microcrystals of an Ir^(Ⅲ)complex. This work demonstrates an appealing strategy of constructing chiral micro/nano-architectures for potential applications in chiral nanophotonics.

Spin-Enhanced C-C Coupling in CO_(2)Electroreduction with Oxide-Derived Copper

Electrocatalytic reduction of carbon dioxide(CO_(2))to multicarbon(C2+)products involves intricate multiple protons and electron transfer of C-C coupling,which is dictated by not only the intrinsic reactivity but also the spin states of electrons in the catalyst.Here,we observe spin-enhanced CO_(2)reduction(CO_(2)RR)electrocatalytic activity on an oxidederived copper(OD-Cu)catalyst due to the existence of a specific Cu*site that carried the magnetic moments.Due to the correlation of magnetic and catalytic properties in OD-Cu,the current density through the OD-Cu electrode increases by nearly 10%at 350 mT.The field strength and angle dependence of such magnetic field effect(MFE),together with the time-resolved measurements proved that it originated from the alignment of magnetic moments on Cu*sites.The MFE on the electrocatalytic process enabled an enhancement(up to 15%)of the CO_(2)RR Faradaic efficiency using the OD-Cu catalyst.Importantly,the enhancement was attributed to the spinantiparallel alignment of electrons to promote C-C coupling on asymmetric Cu*-Cu sites;consequently,the optimal bias was reduced by∼0.2 V under the magnetic field for C2 products with Faradaic efficiency>30%and selectivity>75%.Our work uncovers a new paradigmfor spin-enhanced catalysis applicable to a broad range of chemical reactions involving spin singlet products.

Aromaticity Concerto in Polycyclic Conjugated Hydrocarbons:Fusion Pattern on Combined Aromaticity Strategy Leads to Distinctive Excited State Photophysics of Dinaphthopentalenes

Understanding the structure-property relationships in polycyclic conjugated hydrocarbons(PCHs)is crucial in controlling their electronic properties and developing new optically functional materials.Aromaticity is a fundamentally important and intriguing property of numerous organic chemical structures and has stimulated a myriad of experimental and theoretical investigations.Exploiting aromaticity rules for the rational design of optoelectronic materials with the desired photophysical characteristics is a challenging yet fascinating task.Herein we present an in-depth computational and spectroscopic study on the structure-property relationships of dinaphthopentalenes(DNPs).Results highlight that the different fusion patterns between 4nπand 4n+2πunits endow these PCHs with the tunable aromaticity in the ground state/excited state,which leads to the diverse electronic structures and consequently the distinctive excited state photophysics.Accordingly,we propose a combined aromaticity design strategy for rationally modulating and tailoring electronic and optical properties of PCH skeletons.These outcomes not only present a full picture of the excited state dynamics of the DNP system and afford a new class of efficient singlet fission-active materials but also provide some basic guidelines for exploiting aromaticity rules to design and develop new optical function materials.

Defective g-C_(3)N_(4)supported Ru_(3)single-cluster catalyst for ammonia synthesis through parallel reaction pathways

Designing catalyst to achieve ammonia synthesis at mild conditions is a meaningful challenge in catalysis community.Defective g-C_(3)N_(4)nanosheet supported single-cluster ruthenium and iron catalysts were investigated for their ammonia synthesis performance.Based on density functional theory(DFT)calculations and microkinetic simulations,Ru_(3)single-cluster anchored on defective g-C3N4 nanosheet(Ru_(3)/Nv-g-C_(3)N_(4))has a turnover frequency(TOF)5.8 times higher than the Ru(0001)step surface at industrial reaction conditions of 673 K and 100 bar for ammonia synthesis.In other words,similar TOFs could be achieved on Ru_(3)/Nv-g-C_(3)N_(4)at much milder conditions(623 K,30 bar)than on Ru(0001)(673 K,100 bar).Our computations reveal the reaction proceeds parallelly on Ru_(3)/Nv-g-C_(3)N_(4)through both dissociative and alternative associative mechanisms at typical reaction conditions(600–700 K,10–100 bar);N–N bond cleavage of*N2 and*NNH from the two respective pathways controls the reaction collectively.With increasing temperatures or decreasing pressures,the dissociative mechanism gradually prevails and associative mechanism recedes.In comparison,Fe_(3)/Nv-g-C_(3)N_(4)catalyst shows a much lower catalytic activity than Ru3/Nv-g-C_(3)N_(4)by two orders of magnitude and the reaction occurs solely through the dissociative pathway.The finding provides a prospective candidate and deepens the mechanistic understanding for ammonia synthesis catalyzed by single-cluster catalysts(SCCs).

Tuneable red,green,and blue single-mode lasing in heterogeneously coupled organic spherical microcavities

Tuneable microlasers that span the full visible spectrum,particularly red,green,and blue(RGB)colors,are of crucial importance for various optical devices.However,RGB microlasers usually operate in multimode because the mode selection strategy cannot be applied to the entire visible spectrum simultaneously,which has severely restricted their applications in on-chip optical processing and communication.Here,an approach for the generation of tuneable multicolor single-mode lasers in heterogeneously coupled microresonators composed of distinct spherical microcavities is proposed.With each microcavity serving as both a whispering-gallery-mode(WGM)resonator and a modulator for the other microcavities,a single-mode laser has been achieved.The colors of the single-mode lasers can be freely designed by changing the optical gain in coupled cavities owing to the flexibility of the organic materials.Benefiting from the excellent compatibility,distinct color-emissive microspheres can be integrated to form a heterogeneously coupled system,where tuneable RGB single-mode lasing is realized owing to the capability for optical coupling between multiple resonators.Our findings provide a comprehensive understanding of the lasing modulation that might lead to innovation in structure designs for photonic integration.

High-efficiency quaternary polymer solar cells enabled with binary fullerene additives to reduce nonfullerene acceptor optical band gap and improve carriers transport

The polymer/small-molecule electron donor and nonfullerene organic electron acceptor are of structural similarity with both donor and acceptor molecules consisting of polycyclic fused-ring backbone and being decorated with alkyl-chains.In this study,we report that the introduction of binary fullerenes(C_(60)-/C_(70)-PCBM and C_(60)-/C_(70)-ICBA)into a nonfullerene binary system PBDB-T:ITIC reduces the polymer-nonfullerene acceptor intermixing,obtaining higher crystallinity with(100)crystal coherence length from 28 to 29–33 nm for the ITIC,and from 14 to 20–24 nm for the PBDB-T,and improved electron and hole mobilities both.Unprecedentedly,such a protocol reduces the ITIC optical band gap from 1.59 to 1.55 eV.As consequences,higher short-circuit current-density(17.8–18.4 vs.15.8 m A/cm^2),open-circuit voltage(0.92 vs.0.90 V)and fill-factor(0.72–0.73 vs.0.68)are simultaneously obtained,which ultimately afford higher efficient quaternary polymer solar cells with power conversion efficiencies(PCEs)up to 12.0%–12.8%comparing to the host binary device with 9.9%efficiency.For the polymer,ITIC,and ICBA/PCBM ternary blends,11%PCEs were recorded.The use of PCBM leads to larger red-shifting in thin film absorption and external quantum efficiency(EQE)response.Such effect is more pronounced when ICBA:PCBM mixture is used.These results indicate the size and shape of C_(60)and C_(70)as well as the substituent position of the second indene unit on C_(60)-/C_(70)-ICBA affect not only the blend morphology but also the electronic coupling in BHJ mixtures:the quaternary device performance increased in sequences of C_(70)-PCBM:C_(70)-ICBA→C_(70)-PCBM:C_(60)-ICBA→C_(60)-PCBM:C_(70)-ICBA→C_(60)-PCBM:C_(60)-ICBA.The resonant soft X-ray scattering(RSoXS)data indicated the most refined phase separation in the C_(60)-PCBM:C_(60)-ICBA based blend,corresponding to its best device function among the quaternary devices.These results indicate that the using of binary fullerenes as the acceptor additives allows for tuning nonfullerene blended film’s optical properties and filmmorphologies,shedding light on the designing high-performance multi-acceptor polymer solar cells.

Hybrid Three-Dimensional Spiral WSe2 Plasmonic Structures for Highly Efficient Second-Order Nonlinear Parametric Processes

Two-dimensional(2D)layered materials,with large second-order nonlinear susceptibility,are currently growing as an ideal candidate for fulflling tunable nanoscale coherent light through the second-order nonlinear optical parametric processes.However,the atomic thickness of 2D layered materials leads to poor feld confnement and weak light-matter interaction at nanoscale,resulting in low nonlinear conversion efciency.Here,hybrid three-dimensional(3D)spiral WSe2 plasmonic structures are fabricated for highly efcient second harmonic generation(SHG)and sum-frequency generation(SFG)based on the enhanced light-matter interaction in hybrid plasmonic structures.Te 3D spiral WSe2,with AA lattice stacking,exhibits efcient SH radiation due to the constructive interference of nonlinear polarization between the neighboring atomic layers.Tus,extremely high external SHG conversion efciency(about 2.437×10−5)is achieved.Moreover,the ease of phase-matching condition combined with the enhanced light-matter interaction in hybrid plasmonic structure brings about efcient SHG and SFG simultaneously.Tese results would provide enlightenment for the construction of typical structures for efcient nonlinear processes.

Flat-Panel Laser Displays Based on Liquid Crystal Microlaser Arrays

Laser displays,benefiting from the characteristic merits of lasers,have led to the revolution of next-generation display technologies owing to their superior color expression.However,the acquisition of pixelated laser arrays as self-emissive panels for flat-panel laser displays remains challenging.Liquid crystal(LC)materials with excellent processability and optoelectronic properties offer considerable potential for the construction of highly ordered multicolor laser arrays.Here,we demonstrate flat-panel laser displays on LC microlaser pixel arrays through a microtemplate-assisted inkjet printing method.Individual organic red-green-blue(RGB)microlaser pixel arrays were obtained by doping dyes into LCs with photonic band edges to obtain single-mode RGB lasing,leading to a much broader color gamut,compared with the standard RGB color space.Then we acquired periodically patterned RGB pixel matrices by positioning LC microlasers precisely into highly ordered arrays,according to the well-organized geometry of the microtemplates.Subsequently,we demonstrated full-color flat-panel laser displays using the LC microlaser pixel matrices as self-emissive panels.These results provide valuable enlightenment for the construction of next-generation flat-panel laser display devices.

Wavelength-Tunable Single-Mode Microlasers Based on Photoresponsive Pitch Modulation of Liquid Crystals for Information Encryption

Information encryption and decryption have attracted particular attention;however,the applications are frequently restricted by limited coding capacity due to the indistinguishable broad photoluminescence band of conventional stimuli-responsive fluorescent materials.Here,we present a concept of confidential information encryption with photoresponsive liquid crystal(LC)lasing materials,which were used to fabricate ordered microlaser arrays through a microtemplate-assisted inkjet printing method.LC microlasers exhibit narrow-bandwidth single-mode emissions,and the wavelength of LC microlasers was reversibly modulated based on the optical isomerization of the chiral dopant in LCs.On this basis,we demonstrate phototunable information authentication on LC microlaser arrays using the wavelength of LC microlasers as primary codes.These results provide enlightenment for the implementation of microlaser-based cryptographic primitives for information encryption and anticounterfeiting applications.

A Novel BODIPY-Based Low-Band-Gap Small-Molecule Acceptor for Efficient Non-fullerene Polymer Solar Cells

We report herein an efficient A^1-C=C-A^2-C=C-A^1 type small-molecule 4,4＇-difluoro-4-bora-3a,4a-diaza-sindacene （BODIPY） acceptor （A^1= BODIPY and A^2= diketopyrrolopyrrole （DPP）） by following the A-to-A excited electron delocalization via the BODIPY meso-position, the inherent directionality for the excited electron delocalization. The lowest unoccupied molecular orbital （LUMO） delocalizes across over whole the two flanking A^1 and the central A^2, and the highest occupied molecular orbital （HOMO） localizes dominantly on the -C=C-DPP-C=C- segment. The excited electron upon light excitation of the DPP segment delocalizes over both the BODIPY and DPP segments. The acceptor in chloroform shows an unprecedented plateau-like broad absorption between 550 and 700 nm with a large FWHM value of 195 nm. Upon transition into solid film, the acceptor shows absorption in the whole near ultraviolet-visible-near infrared wavelength region （300-830 nm） with a low band gap of 1.5 eV and a maximum absorptivity of 0.85 × 10^5 cm^-1. Introduction of the ethynyl spacer between the A^1 and A^2 and the close BODIPY-to-DPP LUMO energy levels are crucial for the excited n-electron delocalization across over whole the conjugation backbone. A power conversion efficiency of 6.60% was obtained from the ternary non-fullerene solar cell with PTB7-Th：p-DTS（FBTTh2）2 （0.5 ; 0.5） as the donor materials, which is the highest value among the non-fullerene organic solar cells with BODIPY as the electron acceptor material.

An Optically Reconfigurable Förster Resonance Energy Transfer Process for Broadband Switchable Organic Single-Mode Microlasers

Miniaturized lasers with multicolor output and high spectral purity are indispensable for various ultracompact photonic devices.Here,we propose an optically reconfigurable Förster resonance energy transfer(FRET)process to realize broadband switchable single-mode lasing based on in situ activation of acceptors.The stoichiometric ratio of the donor and acceptor in the ready-made microstructures could be modulated readily by precisely activating the acceptors through a photoisomerization process,leading to a reconstructed FRET process to achieve dynamically switchable lasing.Furthermore,dual-color switchable single-mode lasing was realized by selectively constructing the FRET process in an identical coupled microdisks system.These results advance a comprehensive understanding of excited-state dynamics in organic composite material systems,thereby providing new ideas for the rational design of miniaturized photonic materials and devices with desired performances.

Revealing the Role of d Orbitals of Transition-Metal-Doped Titanium Oxide on High-Efficient Oxygen Reduction

Precise catalysis is critical for the high-quality catalysis industry.However,it remains challenging to fundamentally understand precise catalysis at the atomic orbital level.Herein,we propose a new strategy to unravel the role of specific d orbitals in catalysis.The oxygen reduction reaction(ORR)catalyzed by atomically dispersed Pt/Co-doped Ti_(1−x)O_(2) nanosheets(Pt_(1)/Co_(1)-Ti_(1−x)O_(2))is used as a model catalysis.The z-axis d orbitals of Pt/Co-Ti realms dominate the O2 adsorption,thus triggering ORR.In light of orbital-resolved analysis,Pt_(1)/Co_(1)-Ti_(1−x)O_(2) is experimentally fabricated,and the excellent ORR catalytic performance is further demonstrated.Further analysis reveals that the superior ORR performance of Pt_(1)-Ti_(1−x)O_(2) to Co_(1)-Ti_(1−x)O_(2) is ascribed to stronger activation of Ti by Pt than Co via the d-d hybridization.Overall,this work provides a useful tool to understand the underlying catalytic mechanisms at the atomic orbital level and opens new opportunities for precise catalyst design.

Organic composite materials:Understanding and manipulating excited states toward higher light-emitting performance

Organic composite materials have been attracting extensive research interest for light-emitting applications.A wide variety of luminescent organic composite materials have been synthesized,which are of great significance for both the investigation of basic photophysics and the realization of high-performance photonic devices.Function-oriented syntheses of luminescent organic composite materials rely on the understanding and manipulating of molecular excited states.In this review,we focus on the discussion about the structure design and dynamics modulation of the electronic excited states in the organic composite materials.The excited-state structures and dynamics involve singlet/triplet levels,vibronic transition,charge transfer,and energy transfer,and so on,while the light-emitting behaviors include fluorescence,phosphorescence,persistent luminescence,electroluminescence,and lasing.We aim to give insight into the relationship between light-emitting properties and excited states of organic composite materials,which is beneficial for reaching higher tiers of design and applications of luminescent organic composite materials.

Editorial

Welcome to a New Year and the first issue of Volume 4 of CCS Chemistry.We begin this new year having learned much and with a great deal to look forward to for CCS and CCS Chemistry!2022 is the 90th Anniversary of CCS.The society has a rich history that is strongly tied to the development of chemistry in China.

Achieving high short-circuit current and fill-factor via increasing quinoidal character on nonfullerene small molecule acceptor

Recently, the fused-ring based low band gap （LBG） small molecule acceptors （SMAs） have emerged as efficient nonfullerene acceptors. So far, these LBG SMAs are mainly designed with IC （2-methylene-（3- （1,1 -dicyanomethylene）indanone）） or its analogs, the benzo-type electron-accepting （A） units. Compared to benzene, thiophene is less aromatic and thus the thiophene-involving semiconducting molecule has more quinoidal character, which effectively reduces the energy gap between the highest occupied molecular orbit （HOMO） and the lowest unoccupied molecular orbit （LUMO）. Herein, we show that replacing the IC units in ITIC with the CT （cyclopenta[c]thiophen-4-one-5-methylene-6-（1,1-dicyano- methylene））, a thiophene-fused A unit, the quinoidal character is enhanced from 0.0353 on ITIC to 0.0349 on ITCT, the CT-ended SMA. The increase in the quinoidal character reduces the optical band gap and enhances the near IR absorptivity. When blended with the wide band gap （WBG） polymer donor, PBDB-T, an average power conversion efficiency of 10.99% is obtained with a short-circuit current-density （Jso） of 17.88 mA/cm2 and a fill-factor （FF） of 0.723. For comparisons, theJsc is of 16.92 mA/cm2, FF is of 0.655 and PCE is of 9.94% obtained from the ITIC：PBDB-T device. This case indicates that the replacement of the benzene ring on the IC unit with a more polarizable five-member ring such as thiophene is an effective way to enhance the absorption of the near IR solar photons towards designing high-performance nonfullerene polymer solar cells.

Editorial

Time has come to celebrate the one-year birthday of CCS Chemistry!One year ago,we published the inaugural issue of our flagship journal.A lot has happened in the short time since the journal launch,not the least of which has been the global outbreak of the COVID-19 pandemic.We live in an increasingly interconnected world which makes it essential to work together and share our collective knowledge across boarders for the betterment of society.

Triarylamines with branched multi-pyridine groups： modulation of emission properties by structural variation, solvents,and tris(pentafluorophenyl)borane

Six triarylamine derivatives 1–6 with branched multi-pyridine substituents were prepared and characterized. These compounds are distinguished by the substituent on one of the phenyl group with NO2 for 1, CN for 2, Cl for 3, p-C6 H4 OMe for 4, OMe for 5,and NMe2 for 6, respectively. As revealed by single crystal X-ray analysis, these substituents play an important role in determining the configuration of the triarylamine framework and the crystal packing of 1–6. The emission properties of these compounds were examined in different solvents(toluene, CH2 Cl2, acetone, tetrahydrofuran(THF), and N,N-dimethylformamide(DMF)) and in solid states. Distinct dual emissions from the localized emissive state and the intramolecular charge transfer state were observed for compound 5 in CH2 Cl2. Compounds 1 and 6 show apparent aggregated enhanced emissions in acetone/H2 O.The emission properties of these compounds were further modulated by the addition of tris(pentafluorophenyl)borane. In addition, density functional theory(DFT) and time-dependent DFT(TDDFT) calculations have been performed on the ground and singlet excited states to complement the experimental findings.