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In this work, the key O O bond formation step in water oxidation catalyzed by a polyoxometalate-based complex [Mn3(H2O)3(SbW9O33)2]12− was theoretically investigated. The MnV-oxo species rather than MnIV-oxo species, is computed to be responsible for O O bond formation via water nucleophilic attack mechanism. During O O bond formation based on MnV-oxo species, two-state reactivity is found and the energy profile switches from the 13et state to the 15et state through a minimum energy crossing point, which significantly reduces the activation barrier. The observed spin inversion phenomenon in O O bond formation is attributed to the exchange-enhanced reactivity for 15et state, but not for 13et state.

The improvement of the photocatalytic performance of cobaltporphyrin as CO2 reduction catalysts by chemical modification has become a current research hotspot. Here, we contrastively investigate th...

In this study, we present the synthesis of Tb3Ga5O12 nanoparticles doped with Er3+, Yb3+, and Sc3+ ions, prepared using a co-precipitation method. These materials have well-defined magnetic-fluorescence properties. The effects of Yb3+ ion concentration on the structural characteristics, morphology, luminescence, and magnetic properties of the nanoparticles were investigated in detail using X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, photoluminescence spectroscopy, and vibrating sample magnetometer measurements. Under 980-nm laser diode excitation, the nanoparticles displayed bright up-conversion luminescence, showing evidence of resonant energy transfer from the Yb3+ to Er3+ ions. Intense green and red emissions located at approximately 526, 548, and 656 nm were attributed to the radiant transitions of 2H11/2 → 4I15/2, 4S3/2 → 4I15/2, and 4F9/2 → 4I15/2 of Er3+, respectively. These observations indicate that Tb3Ga5O12:Er3+, Yb3+, Sc3+ magnetic–fluorescent bifunctional nanoparticles are promising materials for use in bioimaging and magnetic bio-separation applications.

The PDCBT shows much better performance than P3HT in non-fullerene organic solar cell although the former only replaces hexyl by alkoxycarbonyl group compared with the latter. In this work, we will focus on this tiny difference in structure and huge difference in performance between these two polymers from theoretical perspective. Thus we present a comparative study based on the dependent/time-dependent density functional theory (DFT/TDDFT) calculations and molecular dynamic (MD) simulations. The results reveal that PDCBT not only possesses lower molecular orbital energy levels which leads to the increasement of the open circuit voltage (VOC), but also exhibits better planarity and larger hole mobility than P3HT. In particular, comparing with P3HT system, PDCBT system also displays the higher charge separation rate and smaller charge recombination rate both in hole transfer and electron transfer process at the interface, which promote the enhancement of short-circuit current density. Therefore, this work provides a fundamental understanding of the prominent influence of the replacement of hexyl group by alkoxycarbonyl in P3HT on the cell performance and also provides some theoretical guidance for further optimization of donor materials in non-fullerene organic solar cells (OSCs).

The nature of the 2e/12c bond and its conversion to a carbon-carbon single bond in phenalenyl dimers have prompted a great deal of interests recently. In this work, we theoretically investigated a series of π-stacking phenalenyl derivatives with 2e/12c bonding character by density functional theory (DFT) calculations to elucidate origin of this unusual bond conversion. Results show that bond-conversion of the phenalenyl dimer easily occurs at room-temperature both dynamically and thermodynamically. However, bond-conversion of hetero π-stacking adducts, in which the two center carbon atoms were substituted by boron and nitrogen atoms, respectively, is much more difficult, because the 2e/12c bond is stabilized by its charge transfer character. Consequently, the bond-conversion is an endothermic process, albeit with a low conversion barrier. Interestingly, Lewis acid-base interactions would be induced by substitution of the center nitrogen atom to phosphorus atom. The 2e/12c bond is further stabilized by 5.9 kcal mol-1 and its conversion is also thermodynamically unfavorable.

Inkjet printing technology is one of the most attractive methods for the realization of full-color patterning for displays. In this work, we successfully introduce this technology into fabricating pixelated light-emitting electrochemical cells (LECs). By carefully controlling the poly (3,4-ethylenedioxythiophene)-poly (styrenesulfonate), and cationic Ir(III) complexes ink formulation, as well as their inkjet printing properties, patterned LEC pixels in ultrahigh definition TV format was fabricated, leading to a resolution of 73 pixels per inch. The as-resulted inkjet-printed LEC exhibits a maximum luminance and a current efficiency of 3402 cd/m2, and 7.5 cd/A, respectively, which is close to that of the spin-coated one. This work paves a new way for the fabrication of low-cost material-efficient, pixelated light-emitting electrochemical cells.

In this work, iridium complexes 1–8 bearing bipyridine or pyridine-pyrimidine main ligand and picolinate ancillary ligand have been designed by varying the position of –OCH3 and phenyl groups at the ligands aiming at finding a better choice to design blue phosphors. The results indicate that an appropriate combination of –OCH3 and pyridine-pyrimidine ligand makes the emission wavelength a noticeable blue-shift. Moreover, the further introduction of phenyl group shifts the emission wavelength to a shorter region. In terms of the radiative decay rate constant (kr), the position of –OCH3 has a slight influence on it, but the introduction of phenyl group is conductive to enhancing this value. In particular, the 7 has the largest kr among the designed complexes up to 7.68 × 105 s−1. As for the non-radiative process, 1–6 have high barriers between 3MLCT and 3MC, indicating the difficulty of electron relaxation to the non-emissive 3MC structure. There is no transition state of 3MLCT↔3MC is found for 7 and 8 bearing pyridine-pyrimidine ligand. However, the barriers of all complexes for the S0/3MC minimum energy crossing point reaction are high, which is in favor of avoiding the system relaxes to the S0 geometry by non-radiative path.

The design and synthesis of 3d–4f heterometallic coordination polymers have attracted much interest due to the intriguing diversity of their architectures and topologies. Pyridine-2,6-dicarboxylic acid (H2pydc) has a versatile coordination mode and has been used to construct multinuclear and heterometallic compounds. Two isostructural centrosymmetric 3d–4f coordination compounds constructed from pyridine-2,6-dicarboxylic acid and 4,4′-bipyridine (bpy), namely 4,4′-bipyridine-1,1′-diium diaquabis(μ2-pyridine-2,6-dicarboxylato)tetrakis(pyridine-2,6-dicarboxylato)bis[4-(pyridin-4-yl)pyridinium]cobalt(II)dieuropium(III) octahydrate, (C10H10N2)[CoEu2(C10H9N2)2(C7H3NO4)6(H2O)2]·8H2O, (I), and 4,4′-bipyridine-1,1′-diium diaquabis(μ2-pyridine-2,6-dicarboxylato)tetrakis(pyridine-2,6-dicarboxylato)bis[4-(pyridin-4-yl)pyridinium]cobalt(II)diterbium(III) octahydrate, (C10H10N2)[CoTb2(C10H9N2)2(C7H3NO4)6(H2O)2]·8H2O, (II), were synthesized under hydrothermal conditions and characterized by IR and fluorescence spectroscopy, thermogravimetric analysis and powder X-ray diffraction. Both compounds crystallize in the triclinic space group P\overline{1}. The EuIII and TbIII cations adopt nine-coordinated distorted tricapped trigonal–prismatic geometries bridged by three pydc2− ligands. The CoII cation has a six-coordination environment formed by two pydc2− ligands, two bpy ligands and two coordinated water molecules. Adjacent molecules are connected by π–π stacking interactions to form a one-dimensional chain, which is further extended into a three-dimensional supramolecular network by multipoint hydrogen bonds.

Developing pure organic materials with ultralong lifetimes is attractive but challenging. Here we report a concise chemical approach to regulate the electronic configuration for phosphorescence enhancement. After the introduction of d-pπ bonds into a phenothiazine model system, a phosphorescence lifetime enhancement of up to 19 times was observed for DOPPMO, compared to the reference PPMO. A record phosphorescence lifetime of up to 876 ms was obtained in phosphorescent phenothiazine. Theoretical calculations and single-crystal analysis reveal that the d-pπ bond not only reduces the (n, π*) proportion of the T1 state, but also endows the rigid molecular environment with multiple intermolecular interactions, thus enabling long-lived phosphorescence. This finding makes a valuable contribution to the prolongation of phosphorescence lifetimes and the extension of the scope of phosphorescent materials.

The increased needs for sustainable energy storage devices make it urgent to develop novel supercapacitor electrode materials. An ingenious zipper-like NiCo2O4/Ni(OH)2 composite has been successfully grown on nickel foam via a one-pot hydrothermal method free of any template or catalyst. Owing to its close contact with the substrate, its distinguished zipper-like structure and unique ingredients, the specific capacitance of NiCo2O4/Ni(OH)2 was as high as 2721 mF cm−2 at 1 mA cm−2; 2161 mF cm−2 was obtained even at 50 mA cm−2; and it retained 86% capacity after 10000 cycles. The facile synthesis method and remarkable capacitive performance of the zipper-like NiCo2O4/Ni(OH)2 make it attractive for supercapacitor applications.

When one is trying to maintain original advantageous properties of molecule without increasing the difficulty of synthesis and processing, simultaneously, adding more predictable properties is a pr...

A novel porous triazine-based metal-organic framework, ([Cd (Ligand)]∙2DMF) (1) with strong luminescence, has been constructed via multi-carboxyl ligand 5,5′,5''-((1,3,5-triazine-2,4,6-triyl)tris(azanediyl))tris(3-methylbenzoic acid) under solvothermal conditions. Structural analysis revealed that MOF1 has a three-dimensional (3D) framework which is crystallized in the monoclinic system bearingC2/c space group. The high chemical and thermal stability of synthesized MOF1 has been predicted by powder X-ray diffraction and thermogravimetric analysis techniques. Higher selectivity and sensitivity of MOF1 towards Cu2+ions is remarkable with an adsorption capacity of 90.5 mg/g compared with Mg2+, Mn2+, Ni2+, Co2+, Zn2+, Fe2+ and Cr3+ ions. Results reveal that strong emission of MOF1 can be quenched effectively by a trace amount of copper (3 ppm) and nitrobenzene (0.6 ppm), even in the vapor phase. The extraordinary solvatochromic phenomenon of MOF1 is observed by incorporating acetonitrile guest molecules due to host-guest interactions provided by the carboxyl groups of ligand and imino triazine backbone. Thus, owing to the highly selective and sensitive quenching effect in fluorescence and solvatochromic behavior, MOF1 can be used as a potential sensor for Cu2+, NB, and acetonitrile.

To gain a deep understanding on structure-property relationship of all-small-molecule nonfullerene organic solar cells, donor molecules SM1 and SM2 with and without cyano group substituents, respectively, were selected, for which SM1-based device has obvious higher power conversion efficiency (10.11%) than SM2-based device (5.32%) in the same condition. Here a systemic study combining quantum chemistry with molecular dynamics was conducted to explore what improve the performance of SM1-based organic solar cells from the theoretical perspective. The results indicate that the cyano substituents in SM1 not only could induce a redshift absorption spectrum through decreasing the energy gap but also lead to better intramolecular charge transfer, which is beneficial to charge transfer at donor/acceptor interface. More interestingly, the SM1/acceptor interface presents an additional charge transfer state (CT state) below the first optically Frenkel exciton state (FE state) except that its FE state has stronger absorption compared with SM2/acceptor interface, which plays an important role in improving its charge transfer rate (kinter-CT) through increasing electronic coupling of charge transfer (VDA-CT). Thus it is speculated that molecular design considering additional CT states below FE state is a promising strategy in organic solar cells like SM1-based device with good performance.

Photoredox-mediated iridium/nickel dual catalysis has successfully triggered a series of traditionally challenging carbon–heteroatom cross-coupling reactions. However, detailed mechanisms, such as ...

The symmetry-broken wave function can transform the 1 Σg+ state of C2 from the classic double bonding to the quadruple bonding, where the transformed wave functions of ϕ L and ϕ R are singly occupied by two opposite-spinning electrons. In this article, the effective bond order (EBO) contribution of the fourth bond in C2 is assessed through the overlap integral between ϕ L and ϕ R , namely the value (0.60) is the EBO contribution of the fourth bond in the transformed scheme. Hence, the new EBO is 3.36, which is more equitable than the original EBO (2.15) in the traditional scheme. In addition, the singlet diradical character of the linear polyacetylenic C4 and C6 in the 1 Σg+ state is addressed for the first time. No spin-polarized bonding exists in other linear C2n clusters, because the ionic interaction in the polyacetylenic 1 Σg+ state of C4 is negligible. Moreover, the coupling energy between α and β single electrons in C4 is only 4.0 kcal mol-1 based on the electron spin-flip energy. © 2019 Wiley Periodicals, Inc.

The activity of the biomimetic CoII-based cuboidal water oxidation catalyst (WOC) [CoII4(hmp)4(μ-OAc)2(μ2-OAc)2(H2O)] ([CoII4O4]) and its Ca2+-substitute [CoII3CaO4] were theoretically investigated to evaluate the effect of redox-inactive Ca2+ on water oxidation by CoII-based cuboidal catalyst. Compared with [CoII4O4], the smaller redox potential of [CoII3CaO4] results in the more efficient oxidation-equivalents accumulation for water oxidation. By contrast, the water oxidation by [CoII3CaO4] is identified to be more thermodynamically superior than that for [CoII4O4]. The energy barrier of key O O bond formation step in water oxidation by [CoII3CaO4] is 22.0 kcal/mol and lower than that found for [CoII4O4] (25.0 kcal/mol).

Design and synthesis of metal-organic polyhedra (MOPs) with targeted geometries from predetermined secondary building units (SBUs) is a long-standing challenge in chemistry and material science. Theoretical prediction shows that there are 6 possible polyhedra from the 3-coordinated, 4-coordinated octahedron ((3,4)-c octahedron) to (3,5)-c icosahedron with minimal transitivity (simplest possible). Except for one missing polyhedron (mtr) due to the unfavorable angles, we report five MOPs based on these structures, including an octahedral (3,4)-c VMOP-21 (rdo), an icosahedral (3,5)-c VMOP-25 (trc), and three intermediate derived trinodal (3,4,5)-c VMOP-22-24 (ghm, hmg, xum). Remarkably, all these MOPs obey the minimal transitivity principle and are consistent with geometrical predictions.

Organic solar cells (OSCs) have made rapid advances in power conversion efficiency during the past decades, which is boosted partly by the various designs of new materials, especially in donor mate...

Three new coordination polymers, [Zn(H2L2)(H2O)]n (1), [Cd(H2L2)(H2O)]n (2) and {[Pb(H2L2)]n (3) (H4L = 1,1′-(propane-1,3-diyl)bis(1H-imidazole-4,5-dicarboxylic acid)) have been successfully prepared under hydrothermal conditions. Complexes 1 and 2 are isomorphic and exhibit 2D fes network constructed from interconnected ring-like [M2(H2L)2] (M = Zn or Cd) MBBs. Complex 3 displays a 3D covalent framework with seh-3,5-P21/c net topology built by interconnected ring-like [Pb4(H2L)2] MBBs. Moreover, the thermal stability and fluorescent properties of these complexes were investigated in detail.

In search of high efficient catalysts for the electrochemical reduction of carbon dioxide is of critical importance to convert CO2 into valuable fuels and chemicals. Herein, the CO2 reduction reaction (CO2RR) paths on two dimensional (2D) M3(hexaiminotriphenylezne)2 (M3(HITP)2, M = Fe, Co, Ni, Ru, Rh, and Pd) metal organic frameworks (MOFs) are calculated by means of density functional theory (DFT). The results reveal that the reaction activity of CO2RR depends on the central metal atom of M3(HITP)2 catalyst. Due to the small overpotentials of 0.67 and 0.46 V, Co3(HITP)2 and Rh3(HITP)2 exhibit superior catalytic activity towards CO2 reduction in which the CH3OH is the favorable product. The present work might provide a new strategy to design high efficient electrocatalysts for CO2RR.

Metal-organic polyhedra (MOPs) are promising candidates for many potential applications; however, their use as photocatalysts for hydrogen production has yet to be developed. Herein, the photocatalytic performance of a water-stable Zr-MOP, ZrT-1-NH2 , was evaluated, for the first time, through photocatalytic hydrogen evolution under visible-light irradiation. ZrT-1-NH2 shows clearly enhanced photocatalytic activity (510.42 μmol g-1 h-1 ) for hydrogen production, in comparison with that of other homogeneous crystalline materials. If platinum nanoparticles were introduced into the photocatalytic system, the hydrogen production efficiency of ZrT-1-NH2 could be further improved. For ZrT-1-NH2 , the conspicuous improvement in photocatalysis can be attributed to efficient electron-hole separation, targeted electron transfer, and excellent recombination suppression. Furthermore, ZrT-1-NH2 shows excellent stability during photocatalytic hydrogen evolution over five continuous runs. This work illustrates that MOP-based photocatalysts hold promise for broad applications in the domain of clean energy.

As compared with the promising near-infrared (NIR) absorbing trans-squaraines (SQ), cis-squaraines (HSQ) possess special absorption spectra showing better performance and are being attracted as promising NIR chromophores in dye-sensitized solar cells (DSSCs). For further extending the absorption toward the NIR region, a rigidified dithiophene spacer 4H-Silolo[3,2-b:4,5-b’]dithiophen/e,4,4,-dimethyl (DTS) was introduced into the skeleton of HSQ (HSQ-DTS). A comprehensive analysis on the light harvesting ability, intramolecular charge separation, interfacial electron injection and dye regeneration were conducted by means of density functional theory (DFT) and time-dependent DFT calculations on the dye@(TiO2)38 system. Our results demonstrated that as compared with HSQ, HSQ-DTS could exhibit panchromatic absorption with more favorable charge separation ability, more injected electrons with inhibited charge recombination process due to the larger distance between the cation hole and the semiconductor surface. The superior performance of dye HSQ-DTS satisfied our original design intent. Therefore, based on these inspiring results, another six different rigidified dithiophene spacers (1-6) were also investigated to screen out more efficient cis-squaraine sensitizers. We find 3 with 4H-Phospholo[3,2-b:4,5-b’]dithiophene,4-ethynyl-,4-oxide possesses the best performance with the maximum short-circuit current ( J s c m a x ) achieved 31.60 mAcm−2, which is expected to support future experimental and theoretical studies.

A highly efficient and low-cost catalyst for the carbon dioxide reduction reaction (CO2RR) is of critical importance to convert CO2 into valuable fuels and chemicals. Herein, the potential of several π-conjugated metal bis(dithiolene) complex nanosheets (M3C12S12, where M denotes Fe, Co, Ni, Ru, Rh, and Pd) as CO2RR electrocatalysts was systemically investigated by means of comprehensive density functional theory (DFT) computations. The results reveal that among the studied candidates, Rh3C12S12 nanosheets exhibit the highest CO2RR catalytic activity due to their low limiting potential (−0.43 V) and activation barrier (1.60 eV). In particular, CH4 is identified as the product, and CHO* formation is the potential/rate-determining step. Thus, by carefully controlling the type of metal atoms, M3C12S12 can be utilized as a promising electrocatalyst for the CO2RR, which may provide a new avenue to design novel metal organic framework (MOF)-based electrocatalysts.

A family of lanthanide-based MOFs (Ln-MOFs) with high thermal and chemical stability have been successfully synthesized by a solvothermal method. Owing to the intrinsic robustness of the framework and temperature-dependent luminescence behaviour of lanthanides, Eu3+/Tb3+-mixed MOFs ([(CH3)2NH2]Eu0.036Tb0.964BPTC) have also been successfully synthesized and targeted for developing excellent luminescent thermometers. The obtained mixed Ln-MOF exhibits ratiometric temperature sensing based on the distinguished characteristic emission of lanthanides with a wide temperature range from 77 K to 377 K. Particularly, the temperature sensor shows good linear responses from 220 K to 310 K with the maximum relative sensitivities (Sm) of 9.42% per K at 310 K. This value is comparable to those of the most excellent Ln-MOF thermometers reported. Besides, the temperature-dependent luminescent colours could also be systematically tuned from green, through yellow to red with increasing temperature, which can be clearly and directly observed even by the naked eye or a camera, thus also allowing colorimetric luminescence thermometry.

During the different clinical manifestations and periods in the treatment of hepatocellular carcinoma (HCC), the species and doses of drugs could be optimized to realize personalized therapy for an individual patient. Here, we firstly reported Yin Yang-like ultrasmall nanoparticles-stacked oleic acid–NaYF4:Yb,Er@hollow porous SiO2 nanoparticles (Yin Yang-like OA–UCNPs@HPS NPs) with a hydrophobic eccentric hollow structure and hydrophilic exterior surface possessing a wide pore size distribution via a novel method. The obtained NPs achieved the loading of multiple varisized hydrophobic/hydrophilic guests into the discrete rooms and the release of each one from the independent channels to reduce the undesirable adverse effects of different guests, which greatly favors the selection of drugs for an individual patient and enhances synergistic theranostics. The in vitro and in vivo (cell line-derived xenograft and patient-derived xenograft models) results demonstrated that the HCPT/DOX-loaded NPs could act as excellent theranostics agents for multimodal imaging-guided synergic dual-drug cancer therapy of HCC. Meanwhile, the potential mechanisms of action of the HCPT/DOX-loaded NPs after endocytosis by HCC cells were evaluated. The nanocomposite could further motivate the progress of new architectures of nanocarriers for varisized guest delivery and personalized treatment.

The research of developing new proton-conducting materials via a simple and cost-effective method is vital in fuel cell technology. In this study, two new supramolecular hydrogen-bonded organic networks (SHONs) have been synthesized via a traditional aqueous solution synthesis or an environmentally friendly grinding synthesis method by using sulfonate and N-donor ligands without a solvent. Discrepancies in particle size and micro-morphology were presented in these SHONs synthesized via different synthetic methods, resulting in obvious distinction of proton conductivity in the corresponding compound. Contact angle measurements and field-emission scanning electron microscopy were also used to explain the intrinsic and extrinsic discrepancies in proton conductivity of each compound synthesized by different methods. Density functional theory calculations proved that the polar charge interactions spurred the formation of hydrogen-bonded networks and compound 2 should have a little higher proton conductivity. The formed SHONs exhibited a high proton conductivity value of up to 10−2 S cm−1 under 97% RH, which can potentially be used in proton-exchange membrane fuel cells.

Herein, we presented a series of Be2X4Y2 clusters (X = Li, Na and Y = Li, Na, K) containing Be[triple bond, length as m-dash]Be triple bonds, which were constructed by six alkali metals as electron-donating ligands. By virtue of the electrostatic potential mapping of the precedent Be[double bond, length as m-dash]Be double-π bonded D4h-Be2X4 clusters, the Be2X4Y2trans-bent geometries and the Be[triple bond, length as m-dash]Be triple bonds inside were both well interpreted. More remarkably, we first identified a perfect classical Be[triple bond, length as m-dash]Be triple bond in D4h-Be2Na4K2 and its Wiberg bond index of Be-Be (WBIBe-Be) reached up to 2.43. Meanwhile, our strategy provides a new approach to explain the trans-bent structure caused by terminal coordination.

The photoreduction of carbon dioxide (CO2) into a valuable energy gas (CO and H2) is an efficient approach to address the fossil fuel crisis and mitigate the global warming effect. The development of effective photocatalysts for CO2 reduction is still desirable and challenging. Herein, two novel polyoxometalate-based hybrids with multinuclear cobalt clusters, [Co2.67(SiW12O40)(H2O)4(Htrz)4]·Cl1.33 (Htrz = 1,2,4-triazole) (1) with a binuclear cobalt cluster and [Co3(SiW12O40)(H2O)3(Htrz)6Cl]·Cl·6H2O (2) with a trinuclear cobalt cluster, were synthesized under hydrothermal conditions. Both of them were characterized by single-crystal X-ray diffractions, PXRD, IR, TG and UV–vis spectra. Compound 1 exhibited a 3D structure with 4-connected [SiW12O40] and 3-connected [Co2(Htrz)3(H2O)3] secondary building units (SBUs). The 1D chain of compound 2 was constructed from [SiW12O40] and [Co3(Htrz)6(H2O)3Cl] SBUs. Furthermore, the photoreduction of CO2 under visible light by the two cobalt-based POMs was investigated using [Ru(bpy)3]Cl2·6H2O as a photosensitizer. The CO yields of compounds 1 and 2 were 15 705 and 18 501 μmol g−1 for the CO2 photocatalytic reduction under three hour irradiation at 293 K, respectively. The difference in the photocatalytic performance of 1 and 2 was explained by comparing the energy of the valence band, band gaps and conduction band. The results showed that the photocatalysts incorporated with multinuclear Co clusters could effectively improve photocatalytic activities, thus providing a valuable view to design high performance and cost-acceptable molecular catalysts for CO2 photoreduction.

Two novel orange-emitting iridium (III) complexes (nbi)2Ir (bisq) (1) and (nbi)2Ir (dmbisq) (2) utilizing 2-naphthalen-1-yl-phenyl-1H-benzimidazole as cyclometalated ligands were successfully synthesized and characterized. The effect of substituent groups in the ancillary ligands on their emission properties was systematically investigated. The experimental results indicate that complex 2 modified by introduction of methyl groups into its ancillary ligand exhibited higher photoluminescence and electroluminescence efficiencies than 1 without methyl groups. Such improved emission efficiencies were tentatively attributed to the suppressed intermolecular interactions in the solid state caused by the introduction of the methyl groups. Although the obtained efficiencies herein are not high, this work enlightens us to manipulate the photoluminescence and electroluminescence properties of iridium (III) complexes via reasonable modification in the ancillary ligand.

Two o-carborane derivatives 1 and 2 exhibiting both aggregation induced emission (AIE) and thermally activated delayed fluorescence (TADF) properties were investigated by combining density functional theory with molecular dynamics simulation. The reason for their TADF property was explored. Besides, taking 1 as an example, the AIE phenomenon was also probed by simulating the aggregation process and comparing the photophysical properties of the molecules in different aggregation states (including crystals, water, and films) with the isolated molecule. The results manifest that the separated orbital occupations of the HOMO and LUMO at the respective donor and acceptor units result in a small singlet–triplet energy gap and a favorable TADF feature, which is similar to many typical TADF molecules. In the AIE phenomenon, a much smaller structural change of donor and acceptor units between S1 and S0 states was experienced for the molecules in all aggregate states compared with that for the isolated molecule, decreasing the energy dissipation substantially and enhancing the luminescence efficiency. In addition, o-carborane is conjectured to help in the free rotation of donor and acceptor units for the isolated molecule, which may contribute to AIE. What's more, on the basis of 1 and 2, we designed 3–6 by means of replacing the triphenyltriazine group with other electron-withdrawing groups having lower LUMO energy levels, aiming to obtain this kind of red light emitting material. The results indeed proved our assumption that 3–6 not only present the feature of red light emission but also have both TADF and AIE properties in films.

A metal–organic framework (MOF) {[(CH3)2NH2]2[Cd3(NTB)2(BDC)]}·4DMF (NTB = 4,4′,4′′-nitrilotrisbenzoic acid; BDC = benzenedicarboxylic acid; DMF = N,N-dimethylformamide) (1) was synthesized via the solvothermal method. In 1, [Cd3(CO2)6] SBUs are linked by NTB3− to form a perfectly 2D planar Cd(NTB) sheet, which is further pillared by BDC, resulting in a 3D pillared layer network. It displays highly selective and recyclable properties in the detection of nitroaromatic explosives such as nitrobenzene (NB), 1,2-dinitrobenzene (1,2-DNB), 1,3-dinitrobenzene (1,3-DNB), 1,4-dinitrobenzene (1,4-DNB) and picric acid (PA, also called 2,4,6-trinitrophenol). Additionally, through the comparison of quenching efficiencies, we can differentiate nitroaromatic explosives with different numbers and locations of –NO2 groups. According to the experimental results, 1 has great potential to be a favorable sensor for selective detection of nitroaromatic explosives, especially PA.

A covalent organic framework (COF) featuring a unique light porous structure and silver nanoparticles shows high efficiency in the degradation of environmental pollutants. However, the combination of a COF with silver nanoparticles has never been reported until now. Toward this end, 2,4,6-tris-(4-formylphenoxy)-1,3,5-triazine (TPT-CHO) and hydrazine hydrate were selected as the construction units of the COF material (TPHH-COF), which possesses rich nitrogen and oxygen sites. Then a new type of composite catalyst (Ag@TPHH-COF) was successfully obtained by solution infiltration. The obtained materials were also fully characterized by standard methods. The results showed that the silver nanoparticles (with diameters of 5 ± 3 nm) were uniformly dispersed on the surface and in the interlayer gaps of the TPHH-COF substrate. Catalytic studies showed that Ag@TPHH-COF could catalyze the reduction of the various nitroaromatic compounds (NACs) with high efficiency, such as 4-nitrophenol, 2-nitrophenol, 4-nitroaniline, nitrobenzene, 4-nitrotoluene and 1-butyl-4-nitrobenzene. Ag@TPHH-COF could also catalyze the reduction of organic dyes such as Rhodamine B (RhB), Methylene Blue (MB), Methyl Orange (MO) and Congo Red (CR). Moreover, Ag@TPHH-COF has good reusability and high recovery.

Dye-sensitized solar cells (DSSCs) are the third generation of photovoltaic cells developed by Grätzel and O'Regan. They have the characteristics of low cost, simple manufacturing process, tunable optical properties, and higher photoelectric conversion efficiency (PCE). With an ever increasing energy crisis, there is an urgent need to develop highly efficient, environmentally benign, and energy-saving cell materials. Polyoxometalates (POMs), a kind of molecular inorganic quasi-semiconductor, are promising candidates for use in different parts of DSSCs due to their excellent photosensitivity, redox, and catalytic properties, as well as their relative stability. Following a brief introduction to the development of DSSCs and the potential virtues of POMs in DSSCs, we attempt to make some generalizations about the energy level regulation of POMs that is the underlying theoretical basis for their application in DSSCs, and then we summarize the research progress of POMs in DSSCs in recent years. This is organized in terms of the properties of POMs, namely, electron acceptor, photosensitivity, redox and catalysis, based on the accumulation of our research into POMs over many years. Meanwhile, in view of the fact that the properties of POMs depend primarily on their electronic structural diversity, we keep this point in mind throughout the article with a view to revealing their structure-property relationships. Finally we provide a short summary and remarks on the future outlook. This review may be of interest to synthetic chemists devoted to designing POMs with specific structures, and researchers engaged in the extension of POMs to photoelectric materials.

CsPbBr3 is widely used in solar cells and LEDs for its excellent photoelectric properties that are also attractive for CO2 photoreduction, but it is less used in the photocatalytic reduction of CO2 mainly owing to its limited charge separation efficiency. To alleviate this issue, herein, all-inorganic orthorhombic CsPbBr3 was combined with graphitic carbon nitride (g-C3N4) and the resultant composite (CsPbBr3@g-C3N4) showed enhanced activity in CO2 photoreduction. Under the irradiation of AM1.5 filter for 12 h, CO2 was converted into CH4 and CO with high selectivity to methane (91%) and the total amount of gaseous products up to ∼300 μmol g-1. This reactivity is 6-fold and 4-fold higher than that of pure g-C3N4 and CsPbBr3, respectively. CsPbBr3@g-C3N4 also shows excellent catalytic activity at low concentrations of CO2. Studies of energy band level and steady-state and transient photoluminescence spectroscopy indicated that the incorporation of CsPbBr3 and g-C3N4 increases charge separation, which may result in sharply enhanced catalytic efficiency. This study has provided opportunities for the combination of CsPbBr3 and other semiconductor catalysts for the photocatalytic reduction of CO2.

Development of efficient, selective and low-cost photocatalysts, ideally constructed from Earth-abundant elements, is still a big challenge for CO2 photoreduction. Herein, adopting mixed halides strategy, the activity of all-inorganic perovskites toward CO2 reduction is enhanced sharply under simulated sunlight without photosensitizer, meanwhile maintaining high selectivity of CO and CH4 production. Via regulating ratio of Br and Cl, the yield of CO and CH4 changes obviously and the optimized catalyst is CsPb(Br0.5/Cl0.5)3 with a total yield of CO and CH4 up to 875 μmol/g (selectivity of 99%) which outperforms any other reported halide perovskites and is 4.5 and 9.1 folds higher than that of CsPbBr3 and CsPbCl3 under the same condition. The efficient charge separation and moderate stability in mixed-halide perovskites may account for the excellent performance in CO2 reduction. This study may provide a new strategy in design of high performance and low-cost halide perovskite materials for photocatalysis.

Dinuclear Ir(III) complexes have recently emerged with great promise for organic electroluminescent devices owing to their unique merits such as increased spin–orbit coupling and adjustable photophysical properties. However, most of them require sophisticated doping processes for their engineering, resulting in high production costs. Herein, we developed novel dinuclear Ir(III) complexes, which become weak phosphors in solution but exhibit intensified emission in the solid state. The intermolecular interaction-caused quenching was suppressed perfectly, and the carrier transport abilities were modulated simultaneously, leading to high emission efficiencies in the neat film and balanced charge carrier transport. The green-emitting single-layer nondoped device achieved promising efficiencies with an external quantum efficiency (EQE) of 11.6% and current efficiency (CE) of 40.0 cd A−1. The orange-emitting device realized an EQE of 12.9% and CE of 38.4 cd A−1, which are the highest efficiencies reported to date for solution-processed single-layer nondoped devices and even comparable to that of most reported multilayer doping devices.

Herein, the electronic structures and absorption spectra of a series of transition-metal-substituted polyoxometalates (TMSPs) were systematically investigated to screen promising candidates for the POM/TiO2 nanocomposite film used in DSSCs using the density functional theory (DFT) and time-dependent DFT (TD-DFT) methods. The highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) gaps (H–L gaps) of the studied TMSPs were remarkably influenced by the substituted transition metals in different periods. Specifically, the H–L gaps increase as the atomic number of the substituted transition metals increases in the same period such as Mn4+ < Fe2+ < Co2+ < Ni2+ (the fourth row) and Re6+ < Os6+ (the sixth row). Considering that the LUMO energy levels of all the studied TMSPs were higher than the conduction band (CB) of TiO2 (−4.00 eV), the TMSPs could quickly transport the photoinduced electrons as long as the LUMO energy levels of the used dyes were higher than those of the TMSPs. SiW11X4− (X = Mn6+, Ru6+ and Os6+) may perform well in DSSCs using the metal-free organic dye D149 due to the proper LUMO energy levels between the CB of TiO2 and the LUMO energy of D149 (−2.41 eV). The absorption spectra of SiW11X4− (X = Mn6+, Ru6+ and Os6+) exhibit broad absorptions in the UV–vis region that are more conducive to extend the range of light captured; this contributes to enhancing the photo-to-electric conversion efficiency. Moreover, the absorption of SiW11Mn4− red-shifts when compared with that of SiW11X4− (X = Ru6+ and Os6+), which results from the smallest H–L gap; this indicates that SiW11Mn4− will be a promising high-performance material-modified photoanode. This study opens new opportunities for the development of potential TiO2-modified materials for DSSCs.

A series of cyanide-bridged coordination polymers (CPs), [CuI2(CN)2(bbi)3]n (1, 1D), [{CuII(CN)2}{CuI2(CN)2}(bimb)3] (2, 2D), (H2dip)[CuI4(CN)6] (3, 3D), [{CuI2(CN)2}(bix)]n (4, 3D), and [CuI2(CN)2(bib)] (5, 2D), (bbi = 4,4′-bis(imidazoly)biphenyl, bimb = 1,4-bis(imidazole-l-yl)butane, dip = 1,5-di(1H-imidazol-l-yl)pentane, bix = 1,4-bis(imidazol-1-ylmethyl)benzene, bib = 1,4-bis(1-imidazolyl)benzene), with controllable dimensions have been prepared under hydrothermal conditions by using different types of rigid and flexible bis-(imidazole) ligands. The characterization of all the polymers has been performed by elemental analyses, infrared spectroscopy (IR), thermogravimetric analyses (TGA), powder X-ray diffraction (PXRD), and single crystal X-ray diffraction. 1 displays two noncovalently-bonded parallel one-dimensional (1D) chains, which are woven to produce a three-dimensional (3D) supramolecular architecture by intermolecular forces. For 2, bimb ligands stabilize the copper(I) and copper(II) mixed-valence states to from a (2,6)-connected two-dimensional (2D) network, which then results in a 3D supramolecular network via intermolecular forces. 3 generates an interesting 3D open framework and the protonated dip ligands as templates and charge compensating agents are encapsulated in the tunnel. In 4, bix ligands act as linkers bridging adjacent 2D networks to generate a 3D coordination framework. 5 is a 2D network structure consisting of [CuCN]n zigzag chains and bib ligands. Moreover, 1–5 show thermal stabilities and luminescence properties in the solid state at room temperature.

Seeking novel two-dimensional (2D) materials with a planar hypercoordinate motif is always an attractive theme, especially to meet the demand for specific functional applications. Here, we identify entirely planar pentacoordinate carbon (ppC) transition-metal carbide (α-TMC, TM = Co, Ni, and Cu) monolayers in their ground states through the swarm-intelligence structure search method and first-principles calculations. In these TMC monolayers, each carbon atom is bound with four transition-metal atoms and one neighboring carbon atom, forming a hexagonal C2@TM6 subunit in a novel topology. Their excellent structural stability is confirmed by the superior cohesive energy and the positive phonon modes. The lower cohesive energy and thermal stability of the CuC monolayers than those of the CoC and NiC monolayers is interpreted by higher electron transfer and lower electron donation/back-donation between TM and C atoms, which is also confirmed by the SSAdNDP analysis. Their magnetic character is distinct at the spin-polarized hybrid HSE06 level. The CoC monolayers are antiferromagnetic, the NiC monolayers are ferromagnetic and the CuC monolayers are non-magnetic. More interestingly, the unusual C2@TM6 subunit determines the excellent mechanical stabilities of TMC monolayers. Therefore, these three TMC monolayers with diverse electronic and magnetic properties are anticipated to be synthesized and applied in spintronics, electronics and mechanics.

The photocatalytic reduction of CO2 to value-added methane (CH4) has been a promising strategy for sustainable energy development, but it is challenging to trigger this reaction because of its necessary eight-electron transfer process. In this work, an efficient photocatalytic CO2-to-CH4 reduction reaction was achieved for the first time in aqueous solution by using two crystalline heterogeneous catalysts, H{[Na2K4Mn4(PO4) (H2O)4]⊂{[Mo6O12(OH)3(HPO4)3(PO4)]4[Mn6(H2O)4]}·16H2O (NENU-605) and H{[Na6CoMn3(PO4)(H2O)4]⊂{[Mo6O12(OH)3(HPO4)3(PO4)]4[Co1.5Mn4.5]}·21H2O (NENU-606). Both compounds have similar host inorganic polyoxometalate (POM) structures constructed with strong reductive {P4Mo6V} units, homo/hetero transition metal ions (MnII/CoIIMnII) and alkali metal ions (K+ and/or Na+). It is noted that the {P4Mo6V} cluster including the six MoV atoms served as a multi-electron donor in the case of a photocatalytic reaction, while the transition metal ions functioned as catalytically active sites for adsorbing and activating CO2 molecules. Additionally, the presence of alkali metal ions was believed to assist in the capture of more CO2 for the photocatalytic reaction. The synergistic combination of the above-mentioned components in NENU-605 and NENU-606 effectively facilitates the accomplishment of the required eight-electron transfer process for CH4 evolution. Furthermore, NENU-606 containing hetero-metallic active sites finally exhibited higher CH4 generation selectivity (85.5%) than NENU-605 (76.6%).

Three new high-dimensional cucurbit[6]-based metal-organic rotaxane frameworks [Co2(PR43)(BDC)2Cl2]·4H2O (1), [Co2(PR43)(BTC)2]·6H2O (2) and [Co2(PR43)(BPT)2]·20H2O (3) were obtained via the hydrothermal synthesis method. Compound 1 comprised a two-dimensional layered structure, while compounds 2 and 3 exhibited three-dimensional pillared structures. All the compounds showed good thermal stabilities. Furthermore, the magnetic properties of compounds 1-3 were also investigated in detail.

In this study, a triazine-based nanoporous metal–organic framework (MOF1) using the tricarboxyl ligand 5,5′,5′′-((1,3,5-triazine-2,4,6-triyl)tris(azanediyl))tris(2-methylbenzoic acid) was solvothermally synthesized. High thermal and chemical stability of MOF1 was established by thermogravimetric and powder X-ray diffraction analysis. Owing to its porous structure with potential nitrogen chelating sites, MOF1 could selectively adsorb the Cu2+ ions over the Mn2+, Ni2+, Co2+, and Zn2+ ions, and the chromatographic separation of the Co2+ ion was achieved from a mixed solution containing Co2+ and Cu2+. Moreover, MOF1 could selectively adsorb and separate cationic dyes on the basis of ionic selectivity rather than size selectivity. Furthermore, the nanoporous MOF1 was used as a host to encapsulate luminescent species, and it displayed a characteristic luminescent color (green for Tb3+ and red for Eu3+); moreover, we tuned the luminescence properties of the MOF1 to achieve white light emission with good color quality.

A metal–oxygen cluster (Fe28) was certified to show inherent peroxidase-like performance, which could catalyze the oxidation of the peroxidase substrate 3,3′,5,5′-tetramethylbenzidine (TMB) using H2O2 in aqueous solution for the first time. The compound Fe28 as a peroxidase mimic displayed multi-functional applications in the detection of H2O2, glucose and dopamine. The TMB/Fe28/H2O2 system supplied a simple colorimetric approach for the detection of H2O2 and glucose with good sensitivity and had a linear range from 2.62 × 10−5 mol L−1 to 1.57 × 10−4 mol L−1 and 3.92 × 10−6 mol L−1 to 3.14 × 10−5 mol L−1, respectively. Moreover, the Fe28 cluster could detect dopamine without H2O2 with a linear range from 4.62 × 10−5 mol L−1 to 4.16 × 10−4 mol L−1. Moreover, the Fe28 cluster was low-priced, easy to synthesize and extremely effective in a colorimetric assay, which could lead to new opportunities for the development and application of metal–oxygen clusters.

An external electric field (EEF), as a metal-free catalyst, catalyzing the Markovnikov hydrosilylation of styrene was studied for the first time. As compared to the field-free situation, the barrier height was almost halved upon the application of EEF with a field strength of 180 × 10−4 a.u. in the direction perpendicular to the “bond axis”. Therefore, the use of EEF not only resolved the questions of the separation of homogeneous catalysts from the reaction mixture, but also facilitated the reaction by decreasing its barriers. Furthermore, we found that the lower the energy of the transition state (TSX) and the higher the energy of the HOMO of the reactant (R1′), the lower the barrier height of hydrosilylation. Hopefully, this study can provide guidance toward experiments involving an external electric field.

The recent discovery of a class of desirable anode materials in metallic two-dimensional (2D) transition-metal (TM) carbides has reignited great interest in the search for high-performance rechargeable lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs). Using an unbiased structure search combined with first-principles calculations, here we identify an entirely planar NiC3 monolayer as a highly symmetric anode material that fully utilizes the active adsorption sites in the NiC4 unit and maintains the original active adsorption sites in the n-biphenyl unit. The outstanding stability of the NiC3 monolayer is confirmed by its superior cohesive energy, positive phonon modes, high thermal stability and strong mechanical stability. Intriguingly, the current design of entirely planar NiC3 monolayer demonstrates extraordinary ultrahigh storage capacity, fast charge/discharge capability and low open-circuit voltage. In particular, the capacity for Li and Na storage on the NiC3 monolayer reaches 1698 mA h g−1, ∼33% higher than the previously reported record (1278 mA h g−1 in puckered TiC3 monolayer) for 2D materials. The present results have broad implications for other 2D carbides as reversible anode materials for LIBs and SIBs that likely harbor similar novel functional performance.

A newly prepared tetraphenylethylene-based (TPE-based) covalent organic polymer (COP) named COP-1 exhibits high selectivity for sensing Fe3+ and the limit of detection (LOD) for Fe3+ is 0.42 μM, which is lower than the reported metal-free porous polymers. Furthermore, a WLED is fabricated and the CIE coordinates are (0.32, 0.33), very close to pure white light. The COP-1 shows potential applications in biosensors of Fe3+ and preparation of WLEDs.

The production of hydrogen via electrochemical water splitting combined with fuel cells is a promising way to realize sustainable energy systems. Herein, we report a simple one-step, scalable glucose-blowing method to synthesize substrate-free porous molybdenum carbide nanoparticles coated with an N-doped porous carbon shell, termed Gb-Mo2C@PC. This catalyst exhibited a good hydrogen evolution reaction (HER) performance with overpotentials of 169 and 188 mV at a current density of 10 mA cm−2 and long-term stability in basic and acid electrolyte, respectively. The HER activity can be ascribed to the fact that the high surface area of its carbon shell can effectively prevent the aggregation of the Mo2C nanoparticles, and their uniform distribution favourably exposes abundant active sites. Moreover, the porous carbon shell coating can accelerate the charge transfer during the process of hydrogen generation and protect the Mo2C nanoparticles from corrosion. Furthermore, this strategy may provide a versatile route for the scaled-up production of cost-effective materials for electrochemical applications.