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Lead halide perovskites (LHPs) with excellent performance have become promising materials for optoelectrical devices. However, as for the dual-color emission LHPs (DELHPs), the low photoluminescence quantum yield (PLQY) hinders their applications. Herein, a simple low-cost room-temperature post-synthetic modification strategy is used to achieve a near-unity PLQY of DELHPs. It is proven that ZnBr2 plays an important role as an inorganic ligand in reducing surface defects to induce a 95.4% increase in the radiative decay rate and a 99.5% decrease in the nonradiative decay rate in the treated DELHPs compared with the pristine DELHPs. The performance of the blue emission from the surface lattice is greatly improved via the modification of ZnBr2. DELHPs with different ratios of blue and green emissions are obtained by changing the specific surface area and ZnBr2 concentration. The distribution and mechanism of Zn2+ are discussed using the research model based on these DELHPs. The first example of the single-layer dual-color perovskite electroluminescence device is realized from DELHPs. This work provides a new perspective for improving the performance of DELHPs, which will greatly accelerate the development of emission materials of LHPs.

Photocatalytic carbon dioxide reduction (CO2RR) is considered to be a promising sustainable and clean approach to solve environmental issues. Polyoxometalates (POMs), with advantages in fast, reversible, and stepwise multiple-electron transfer without changing their structures, have been promising catalysts in various redox reactions. However, their performance is often restricted by poor thermal or chemical stability. In this work, two transition-metal-modified vanadoborate clusters, [Co(en)2]6[V12B18O54(OH)6]·17H2O (V12B18-Co) and [Ni(en)2]6[V12B18O54(OH)6]·17H2O (V12B18-Ni), are reported for photocatalytic CO2 reduction. V12B18-Co and V12B18-Ni can preserve their structures to 200 and 250 °C, respectively, and remain stable in polar organic solvents and a wide range of pH solutions. Under visible-light irradiation, CO2 can be converted into syngas and HCOO- with V12B18-Co or V12B18-Ni as catalysts. The total amount of gaseous products and liquid products for V12B18-Co is up to 9.5 and 0.168 mmol g-1 h-1. Comparing with V12B18-Co, the yield of CO for V12B18-Ni declines by 1.8-fold, while that of HCOO- increases by 35%. The AQY of V12B18-Co and V12B18-Ni is 1.1% and 0.93%, respectively. These values are higher than most of the reported POM materials under similar conditions. The density functional theory (DFT) calculations illuminate the active site of CO2RR and the reduction mechanism. This work provides new insights into the design of stable, high-performance, and low-cost photocatalysts for CO2 reduction.

The solid-solid conversion of Li2S2 to Li2S is a crucial and rate-controlling step that provides one-half of the theoretical capacity of lithium-sulfur (Li-S) batteries. The catalysts in the Li-S batteries are often useless in the solid-solid conversion due to the poor contact interfaces between solid catalysts and insoluble solid Li2S2. Considering that ultrafine nanostructured materials have the properties of quantum size effects and unconventional reactivities, we design and synthesize for the pomegranate-like sulfur nanoclusters@nitrogen-doped carbon@nitrogen-doped carbon nanospheres (S@N-C@N-C NSs) with a seed-pulp-peel nanostructure. The ultrafine S@N-C subunits (diameter ≈5 nm) and effects of a spatial structure perfectly realize the rapid conversion of ultrafine Li2S2 to Li2S. The S@N-C@N-C seed-pulp-peel NS cathodes exhibit excellent sulfur utilization, superb rate performance (760 mAh g-1 at 10.0 C), and an ultralow capacity decay rate of about 0.016% per cycle over 1000 cycles at 4.0 C. The proposed strategy based on ultrafine nanostructured materials can also inform material engineering in related energy storage and conversion fields.

Fabricating proton exchange membranes (PEMs) with high ionic conductivity and ideal mechanical robustness through regulation of the membrane microstructures achieved by molecular-level hybridization remains essential but challenging for the further development of high-performance PEM fuel cells. In this work, by precisely hybridizing nano-scaled bismuth oxide clusters into Nafion, we have fabricated the high-performance hybrid membrane, Nafion-Bi12 -3 %, which showed a proton conductivity of 386 mS cm-1 at 80 °C in aqueous solution with low methanol permeability, and conserved the ideal mechanical and chemical stabilities as PEMs. Moreover, molecular dynamics (MD) simulation was employed to clarify the structural properties and the assembly mechanisms of the hybrid membrane on the molecular level. The maximum current density and power density of Nafion-Bi12 -3 % for direct methanol fuel cells reached to 432.7 mA cm-2 and 110.2 mW cm-2 , respectively. This work provides new insights into the design of versatile functional polymer electrolyte membranes through polyoxometalate hybridization.

Developing high-efficieny and selectivity catalysts for CO2 reduction reaction (CO2RR) is significant in converting solar energy to value-added chemicals, and Z-scheme heterostructures are promising materials for photocatalytic CO2 reduction due to their narrower band gaps and stronger redox reactivity. In this work, via first-principles calculations we have focused on the performance of a Z-scheme triazine-based g-C3N4/TiO2 heterostructure for photocatalytic CO2 capture and reduction. The results reveal that the band gap of g-C3N4/TiO2 calculated using the HSE06 method is 2.18 eV, which is smaller than those of g-C3N4 and TiO2. The electrons in the conduction band (CB) of g-C3N4 have a stronger oxidation ability and holes in the valence band (VB) of TiO2 have a stronger reduction ability. The electronic properties indicate that the construction of a heterostructure enhances the catalytic performance. According to the CO2 reduction pathway, the g-C3N4/TiO2 heterostructure has remarkable catalytic activity for CO2 reduction to CH4 and CH3OH; the hydrogenation of CO2 → COOH* with a ΔG of 1.29 eV is identified as the rate determining step. The present work not only emphasizes the significance of the Z-scheme heterostructure, but also paves a promising way for photocatalytic CO2RR.

The efficient activation of the adsorbed N2 is the initial and crucial step in the electrochemical nitrogen reduction reaction (NRR), but remains a long-standing challenge. Attaching long-distance heterometal M and M′ metals from the two ends of NN (like a curved bonding in Ag2C2) is an ingenious strategy to promote the activation and polarization of the intrinsic triple bond during electrocatalysis. Motivated by this strategy and the excellent stability and larger size of the B7-unit, the global-minimum MM′B7 monolayers with elongated heterometal double-sites as promising NRR electrocatalysts have been identified from the 10 179 candidates using high-throughput screening. The TiNbB7 monolayer with a metal distance of 3.56 A exhibits the optimal NRR catalytic activity with the limiting potential of 0.04 V and the kinetic energy barrier of 0.75 eV through the mixed mechanism, together with a strong capability of suppressing the competitive hydrogen evolution reaction and the surface oxidation. The other eight global-minimum systems (NbMoB7, ScHfB7, ScNbB7, ScTaB7, ScZrB7, TiHfB7, TiNbB7 and ZrHfB7) also possess excellent catalytic activity, and the highest limiting potential is only 0.62 V. These data adequately verify that long-distance heterometal double-sites are an excellent strategy to active and polarize the NN triple bond due to the elongated bonding length, asymmetric interaction and favorite orbital matching for the side-on adsorbed N2 molecule on double-sites. Most importantly, this work opens a new avenue to design and develop efficient NRR electrocatalysts with the long-distance heterometal double-sites.

Antibiotics as newly emerging organic pollutants are arousing more and more serious environmental issues. Meantime, metal–organic frameworks (MOFs) are considered as promising adsorbents to remove antibiotics. To overcome the limitations of large-scale applications for MOFs in the powder form, herein, we proposed a strategy of in-situ growth ZIF-67 onto polyaniline (PANI) modified regenerated cellulose aerogel (RCA). First, RCA was obtained by chemical cross-linking and physical cross-linking method. Then, PANI played the role of metal chelated layers, which were coated on RCA by in-situ polymerization. Finally, ZIF-67 nanocrystals were in-situ growth on the surface of the PANI coated regenerated cellulose aerogel to synthesise the composite adsorbent ZIF-67/PANI/RCA. The loading mass ratios of ZIF-67 on RCA and PANI/RCA were 25.39% and 42.38%, respectively, which indicates that PANI as interface layers can effectively promote the in-situ growth of ZIF-67 compared with pure RCA. The obtained composite adsorbent (ZIF-67/PANI/RCA) was applied for the adsorption of tetracycline (TC) with high adsorption capacity (409.55 mg·g−1) and good recycling ability. After six cycles of adsorption–desorption, the removal efficiency toward TC was still over 94%. This strategy may provide an effective and versatile pathway to increase MOF loading mass on aerogel and sequentially branch out their applications in pollutant treatment fields.

Ferroelectricity has an excellent reversible polarization conversion behavior under an external electric field. Herein, we propose an interesting strategy to alleviate the shuttle effect of lithium-sulfur battery by utilizing ferroelectric metal-organic framework (FMOF) as a host material for the first time. Compared to other MOF with same structure but without ferroelectricity and commercial carbon black, the cathode based on FMOF exhibits a low capacity decay and high cycling stability. These results demonstrate that the polarization switching behaviors of FMOF under the discharge voltage of lithium-sulfur battery can effectively trap polysulfides by polar-polar interactions, decrease polysulfides shuttle and improve the electrochemical performance of lithium-sulfur battery.

The development of inexpensive and efficient bifunctional electrocatalysts is significant for widespread practical applications of overall water splitting technology. Herein, a one-pot solvothermal method is used to prepare hollow porous MnFe2 O4 spheres, which are grown on natural-abundant elm-money-derived biochar material to construct MnFe2 O4 /BC composite. When the overpotential is 156 mV for both the oxygen evolution reaction and the hydrogen evolution reaction, the current density reaches up to 10 mA cm-2 , and its duration is 10 h. At 1.51 V, the overall water decomposition current density of 10 mA cm-2 can be obtained in 1 m KOH. This work proves that elm-money-derived biochar is a valid substrate for growing hollow porous spheres. MnFe2 O4 /BC give a promising general strategy for preparing the effective and stable bifunctional catalysis that can be expand to multiple transition metal oxide.

Systematic design and self-assembly of metal-organic polyhedra with predictable configuration has been a long-standing challenge in crystal engineering due to the difficulty of finding suitable building units. Herein, we are focused on a concave polyoxovanadate cluster [V6O6(OCH3)9(SO4)4]5- that can be generated in situ under the exact reaction conditions. Based on this cluster, a potential trivalent molecular building block [V6O6(OCH3)9(SO4)(CO2)3]2- can be obtained by the bridging-ligand-substitution strategy that possesses appropriate angle information for the design of molecular cubes. Utilizing the face-directed assembly of the trivalent molecular building block and a diverse set of tetratopic carboxylate linkers, a series of metal-organic cubes VMOC-1 to VMOC-5 with the same topology but different functionalities and dimensions are designed and constructed. The inclusion study made with VMOC-3 as an example has shown that they are potential molecular receptors and can selectively capture size-matching polycyclic aromatic hydrocarbon guest molecules.

The search for highly stable hydrogen evolution reaction (HER) catalysts with high activity, multiple active sites, and excellent electrical conductivity is crucial to promote the development of hy...

For high reactivity but poor stability of homogeneous metal complexes in CO2 photoreduction, development of durable systems is still a big challenge. Herein, pentanuclear Co(II) complex [Co5(btz)6(NO3)4(H2O)4] (1, btz = benzotriazolate) is explored for converting CO2 to syngas which shows high stability and reactivity in both pure and diluted CO2. Compared with mononuclear structure, multinuclear complex exhibits 212-fold enhancement in reactivity, up to ~2748 TONs, with wide adjustability of H2/CO ratio from 16:1 to 2:1. This reactivity could be maintained over 200 h which is an order of magnitude higher than the durability of mononuclear complex and exceeds most reported homogeneous molecular catalysts. High reactivity is also achieved in extreme low CO2 content (5%). Structural analysis and density functional theory (DFT) calculations support that multinuclear structure and the low energy barrier for photocatalytic intermediate may account for the durable and efficient performance of complex 1. The multinuclear strategy is also adopted to nickel complex. This work probes origin of metal-node-dependent performance for CO2 photoreduction, providing new insights in design of durable and efficient metal complexes for photocatalysis and other applications.

Porous covalent organic frameworks (COFs), as an emerging material, have the characteristics of high stability, large series of components, easy synthesis, modification, and adjustable amplitude. They have the potential to become good catalysts. Bromine, as a halogen, has attracted intensive interest for the modification of photocatalysts for photocatalytic reactions. It is feasible to enhance the activity and selectivity of the material by facile functionalization of the reticular parent structure's electron-withdrawing groups. In addition, the conjugation effect of bromine, further delocalizing the electrons of the COF, is beneficial to the progress of many photocatalytic reactions. Reports on the modification of COFs by bromine functional groups to improve the catalytic performance have not been found so far. Here, TAPP [5,10,15,20-tetrakis(4-aminophenyl)porphyrin] and 2,5-dibromo-1,4-benzenedialdehyde instead of terephthalaldehyde were chosen to synthesize a porphyrin-based COF (TAPBB-COF) by the solvothermal method. As expected, the valence band (VB) of TAPBB-COF is thus adjusted to a more suitable position. Additionally, the CO production when using TAPBB-COF under full-wavelength light for 12 h was 295.2 μmol g-1 , which was three times that of COF-366, and the new material has good recycling stability and selectivity (95.6 %). Theoretical calculations indicate that the nitrogen of the porphyrin ring and the Schiff base, and the bromine in TAPBB-COF contribute greatly to the activation of H2 O and the conversion of CO2 in the photoreaction.

At present, the fixation of CO2 always requires it to be extracted from the atmosphere first, which leads to more energy consumption. Thus, direct photoreduction of low-concentration CO2 to useful chemicals (e.g., syngas) under sunlight is significant from an energy-saving and environmentally friendly perspective. Here, the design and fabrication of a [Ru(bpy)3 ]/[Co20 Mo16 P24 ] composite is demonstrated for visible-light-driven syngas production from diluted CO2 (3-20 %) gas with a high yield of approximately 1000 TONs (turnover number of syngas). This activity is an order of magnitude higher than the reported system with [Ru(bpy)3 ]2+ participation. With evidence from ultrafast transient absorption, GC-MS, 1 H NMR spectroscopy and in situ transient photovoltage tests, a clear and fundamental understanding of the highly efficient photoreduction of CO2 by the [Ru(bpy)3 ]/[Co20 Mo16 P24 ] composite is achieved. Making use of the structure and property designable polyoxometalates towards the photo-fixation of CO2 is a conceptually distinct and commercially interesting strategy for making useful chemicals and environmental protection.

Zn=Zn double bonded-especially double-π bonded-systems are scarce due to strong Coulomb repulsion caused by the Zn atom's internally crowded d electrons and very high energy of the virtual π orbitals in Zn2 fragments. It is also rare for Zn atoms to exhibit negative oxidation states within reported Zn-Zn bonded complexes. Herein, we report Zn=Zn double-π bonded octahedral clusters Zn2 M4 (M=Li, Na) bridged by four alkali metal ligands, in which the central Zn atom is in a negative oxidation state. Especially in D4h -Zn2 Na4 , the natural population analysis shows that the charge of the Zn atom reaches up to -0.89 |e| (-1.11 |e| for AIM charge). Although this cooperation inevitably increases the repulsion between two Zn atoms, the introduction of the s1 -type ligands results in occupation of degenerated π orbitals and the electrons being delocalized over the whole octahedral framework as well, in turn stabilizing the octahedral molecular structure. This study demonstrates that maintaining the degeneracy of the π orbitals and introducing electrons from equatorial plane are effective means to construct double-π bonds between transitional metals.

Many interesting multifunctional materials are obtained under the application of an external electric field, which arouses extensive interest of experimental and theoretical researchers. In the pre...

Developing highly stable materials for harmful ion detection in a water environment is of much importance and challenging. Here, two three-dimensional porous structures (termed as Eu-MOF and Tb-MOF) were successfully constructed by the strategy of anchoring Eu3+/Tb3+ and rigid 1,2,4,5-benzenetetracarboxylic acid (H4BTEC) imidazole units (H3ICA) onto its frameworks. The obtained Eu-MOF and Tb-MOF display high water stability and fluorescence stability up to 30 days. Furthermore, luminescent studies reveal that Eu-MOF and Tb-MOF show rapid, recursive, and simultaneous sensing Fe3+ and Cr2O72-/CrO42- ions in water. In addition, the sensing function possesses remarkable cyclicity and selectivity even with the existence of other analogous ions.

The physical confinement and chemical catalysis of lithium polysulfides (LiPSs) are effective approaches to improve the performance of lithium–sulfur (Li–S) batteries. How to effectively combine physical confinement and chemical catalysis has become the focus of research. Herein, micro–mesoporous carbon (MMC) embedded with well-dispersed ultrafine CoS2 (uCoS2) nanocrystals as an efficient sulfur host is presented. As expected, the obtained S/uCoS2@MMC cathode can achieve a synergistic effect of physical confinement and chemical catalysis of LiPSs through micro–mesoporous structures and well-dispersed uCoS2 nanocrystals. Furthermore, the MMC with a high conductive specific surface area, uniform pore size and micro–mesoporous structure can realize homogeneous loading of sulfur and physical adsorption of LiPSs. Owing to these excellent qualities, the S/uCoS2@MMC cathode delivers outstanding initial capacities up to 1227 mA h g−1 at 0.1C. More significantly, a capacity of 606 mA h g−1 is maintained after 1000 cycles at 1C (a very low capacity decay rate of only 0.032% per cycle). It can be seen that the MMC embedded with well-dispersed uCoS2 nanocrystals as the sulfur host has great application prospects in Li–S batteries.

Light irradiation can affect electronic properties of catalysts and the introduction of appropriate light into electrocatalysts may have a significant impact on the electrocatalytic process; however, this has not been fully studied. Herein, we propose a photo-activated process cascaded electrocatalysis for CO2 reduction to produce syngas over a core–shell ZIF-8@Co/C catalyst. Under light irradiation, the onset potential and overpotential of ZIF-8@Co/C positively shift by 40 and 200 mV, and the syngas production is enhanced 5.2-fold at a bias potential of −0.9 V vs. RHE. It is noteworthy that the electric energy efficiency is enhanced by 30%. Deducting syngas generated by electricity, the solar-to-syngas conversion efficiency (joule to joule) is as high as 5.38%, which outperforms reported photoelectrochemical systems. These devices also relatively maintain high efficiency in neutral pH aqueous solution. Dedicated experiments and in situ transient photovoltage studies demonstrate that the cascaded photo-activation of CO2 and H+ in electrocatalysis accounts for the outstanding catalytic performance.

Adequate studies have confirmed that polyoxometalates (POMs) are preeminent multi-electron donors and metalloporphyrins are electrochemically generated active catalysts for the CO2 reduction reaction. Integrating electron-rich POMs with metalloporphyrins in a metallic and stable organic framework can create facile and fascinating heterogeneous electrochemical catalysts by merging their complementary advantages and extensive promising possibilities. Herein, we designed and screened a series of stable and metallic two-dimensional (2D) polyoxometalate–metalloporphyrin organic frameworks (TM–PMOFs, TM in porphyrin = Fe, Co, Ni, Cu, Zn, Ru, Rh, Pd, Os, Ir, or Pt) constructed by linking reductive Lindqvist-type hexamolybdate ([Mo6]2e/2H) with 4-connected tetra-(4-aminophenyl) metalloporphyrin (TM-TAPP) building structs through the MoN triple bond, whose CO2 electrochemical reduction performances and processes are studied in detail by means of density functional theory (DFT). Our computations reveal that the Lindqvist-type clusters [Mo6]2e/2H act as multi-electron regulators for the reduction reaction, and then the most promising catalyst for the reduction from CO2 to CH4 has the lowest theoretical driven potential (0.41 V). Moreover, the [Mo6]2e/2H units inside are easily reduced from the [Mo6] with a driven potential (0.08 V). Our work will encourage more experimental studies to further explore metallic 2D PMOF materials for CO2 electrochemical reduction.

Direct CO2 conversion from flue gas into high-value products is of great significance not only in relieving environmental burden but alleviating the energy crisis by a low-cost and energy-saving avenue, yet few studies in this aspect have been reported. Herein, we report metal-node-dependent catalytic performance for solar-energy-powered CO2 reduction to formate in simulated flue gas by bimetallic Ni/Mg-MOF-74. The yield of HCOO− with Ni0.75Mg0.25-MOF-74 as a catalyst in pure CO2 is 0.64 mmol h−1 gMOF−1 which is higher than that of Ni-MOF-74 (0.29 mmol h−1 gMOF−1) and Ni0.87Mg0.13-MOF-74 (0.54 mmol h−1 gMOF−1), whereas monometallic Mg-MOF-74 is almost inactive, indicating that reactivity relies on metal nodes. In simulated flue gas without water vapor at 20 °C, ∼80% of the reactivity in pure CO2 is retained, with HCOO− generation reaching 0.52 mmol h−1 gMOF−1. This activity is comparable to that of the best MOF catalysts in pure CO2, demonstrating that Ni/Mg-MOF-74 not only overcomes the limitation from CO2 concentration, but also has good resistance to other gas components in flue gas at 20 °C. DFT calculations reveal the high output for HCOO− from two crucial factors: strong CO2 binding affinity of Mg sites, and the synergistic effect of Mg and Ni leading to the stabilization of the key *OCOH intermediate with an appropriate energy barrier. This work paves a new route for double-metal MOFs to enhance the CO2 photoreduction reactivity in flue gas.

The electronic properties of dyes can be readily tuned by modifying the structure. Herein, the polyoxometalate (POM)-based dyes derived from dye XW11 with new patterns, donor-acceptor-π linker-acceptor (D-A-π-A) structure (dye 1), and D-π-A-π-A structure (dye 2) were designed by inserting a POM moiety besides the extensively exploited D-π-A structure (dye 3). Based on density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations, the configuration effect on the designed dyes was investigated. The results indicate that dye 3 possesses the largest short-circuit photocurrent density JSC due to the red-shifted absorption spectra, superior intramolecular charge transfer (ICT) parameters and the largest electron injection efficiency. At the same time, dye 1 with a D-A-π-A structure not only benefits the conduction band energy shift, but also retards the charge recombination and dye aggregation effect, which is beneficial for open-circuit photovoltage VOC. Moreover, the dynamics analysis of interfacial electron transfer shows that the electrons in dye 1 are almost completely injected after 14 fs, while it takes a long time for dyes 2 and 3. The present work is expected to establish a structure-property relationship for future dye design.

In this work, the mechanism of water oxidation catalyzed by a tricopper-containing polyoxometalate (POM) [(SbW9O33)2CuII3(H2O)3]12− ([POM-CuII2CuII OH2]12−), including (i) the deprotonation oxidation and (ii) O O bond formation steps, was theoretically investigated for the first time. Calculations suggest that the Cu center is redox-inert and remains bivalence throughout the catalytic reaction. This is significantly different from the Ru-, Co- and Mn-containing POM-based water oxidation catalysts in which the metal centers (Ru, Co, Mn) are sequentially oxidized and reduced during catalytic reaction. In deprotonation oxidation step, two hydrogen atoms are removed from one water ligand. Therefore, an unusual metal-oxyl-radical species [POM-CuII2CuII O ]12− is obtained, in which two unpaired electrons are assigned to the active O center. A monocopper-containing keggin POM [CuII(O )SbW11O39]5− ([POM-CuII O ]5−) was selected as the model to explore the O O bond formation mediated by [POM-CuII2CuII O ]12−. The O O bond formation was proposed to proceed via the single electron transfer-water nucleophilic attack (SET-WNA) mechanism. Two electrons from the incoming water molecule is step by step transferred to the oxyl-radical ligand of [POM-CuII O ]5−. Furthermore, the SET-WNA process is characterized by two-state reactivity and the observed spin inversions between two potential energy surfaces effectively reduce the activation barrier. Therefore, the present work would provide the promising information for further designing water oxidation catalysts (WOCs).

Electrocatalytic reduction of nitrogen (N2) is considered as a simple, green, and sustainable method for producing ammonia (NH3). Inspired by the recent experimental synthesis of a two-dimensional intrinsically conductive Ni-based covalent organic framework (Mirica et al., J. Am. Chem. Soc., 2019, 141, 11929–11937), here, on the basis of density functional theory (DFT), we explore the electrocatalytic performance of a series of stable and conductive two-dimensional (2D) TM-based covalent organic frameworks (TM-COFs, TM = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Nb, Mo, Ru, Rh, Pd, Ag, W, Ir, Pt, and Au, respectively) toward the N2 reduction reaction (NRR), which are constructed by the robust linkage between 2,3,9,10,16,17,23,24-octaamino-metallophthalocyanine and pyrene-4,5,9,10-tetraone. The computational results show that the 2D conductive Mo-COF exhibits the highest electrocatalytic performance for N2 fixation with a very low overpotential of 0.16 V among the 20 candidates, and can effectively inhibit the competitive hydrogen evolution reaction (HER). The outstanding NRR activity and selectivity of the Mo-COF stem from its inherent superiorities, such as excellent electrical conductivity, significant positive charge and large spin moment on the Mo atom, and appropriate adsorption strength for NRR species. This work will promote more experimental research in this field to discover more highly active COF-based catalysts for advancing sustainable NH3 production.

The performance of MnII/III-monosubstituted heteropolytungstates [MnIII(H2O)GeW11O39]5– ([GT-MnIII-OH2]5–, where GT = GeW11O39) and [MnII(H2O)GeW11O39]6– ([GT-MnII-OH2]6–) as water oxidation catalysts at pH 9 was explored using density functional theory calculations. The counterion effect was fully considered, in which five and six Na+ ions were included in the calculations for water oxidation catalyzed by [GT-MnIII-OH2]5– and [GT-MnII-OH2]6–, respectively. The process of water oxidation catalysis was divided into three elemental stages: (i) oxidative activation, (ii) O–O bond formation, and (iii) O2 evolution. In the oxidative activation stage, two electrons and two protons are removed from [Na5-GT-MnIII-OH2] and three electrons and two protons are removed from [Na6-GT-MnII-OH2]. Therefore, the MnIV-O• species [Na5-GT-MnIV-O•] is obtained. Two mechanisms, (i) water nucleophilic attack and (ii) oxo–oxo coupling, were demonstrated to be competitive in O–O bond formation triggered from [Na5-GT-MnIV-O•]. In ...

Poly(3-hexylthiophene) (P3HT)-based organic solar cells (OSCs) have been developed in recent years because of their advantages such as easy production, low cost, and large-area manufacture. However...

Single-ionic conducting electrolytes are important for the improvement of lithium metal batteries with high energy density and safety. Herein, we propose a new strategy to anchor a large anionic group on the skeleton of metal-organic frameworks (MOFs) and achieve preeminent single-ionic conducting electrolytes. Utilizing a postsynthetic modification method, the trifluoromethanesulfonyl group is covalently coordinated to the amino groups of the UiO-66-NH2 framework. Such a single-ionic conducting solid-state electrolyte (SSE) has a high ionic conductivity (2.07 × 10-4 S cm-1 at 25 °C), a low activation energy of 0.31 eV, a wide electrochemical window up to 4.52 V, as well as a high Li+ transference number of 0.84. Simultaneously, it can effectively inhibit the formation of lithium dendrite. Solid-state batteries assembled with LiFePO4 as the cathode exhibit outstanding rate performance and cyclic stability, especially for low-temperature Li-metal batteries at 0 °C with trace amounts of propylene carbonate as wetting agents. More importantly, the corresponding all-solid-state batteries based on an MOF-based SSE also have nearly 100% Coulombic efficiency at different current densities.

Recently, solution-processable PhOLEDs have been attracting great interest for their low cost and high productivity relative to the vacuum-deposited devices. Similar to vacuum-deposited OLEDs, however, they usually suffer from serious efficiency roll-offs, especially in high brightness. Finding a feasible way and/or designing novel materials to increase efficiencies and reduce roll-offs simultaneously are highly desired. Herein, a new family of solution-processable cyclometalated iridium(III) phosphors with carbazole (

The biodegradable nanoparticles hold tremendous potential in the field of nanomedicine because of the negligible toxicity concerns in healthy tissues/organs. We reported a simple route for the synthesis of pH-responsive biodegradable ZnO nanospheres (ZnO NSs) assembled from ultrasmall particles (sizes ranging from 4 to 8 nm, average 6 nm) with a suitable size. The nanoplatform could be responsively decomposed into small fragments under the weak acid environment to meet the requirement for pH-stimulus drug release and in favor of the biodegradation. The confocal laser scanning microscopy (CLSM) studies showed that the ZnO NSs could be efficiently internalized by cancer cells, and the loaded doxorubicin (DOX) in the NSs could be successfully released under acidic intracellular environment. Notably, the cell viabilities of DOX-loaded NSs with different sizes towards HepG-2 and HeLa cells for different incubation time were investigated, which exhibited dose-dependent and time-dependent effects. Furthermore, in vivo experiments showed that the DOX-loaded NSs displayed a significant antitumor effect (79% average inhibition rate relative to the control group) without distinct side effects. All in all the designed NSs as drug delivery systems not only achieved the excellent cancer chemotherapy but also could be rapidly decomposed or metabolized to reduce their toxicity.

Three nanoscale Nb/W mixed-addendum polyoxometalates, Cs14K4[(Si4W36Nb12O156)Cu(H2O)2]·47H2O, Cs10K8[(Si4W36Nb12O156)Zn(H2O)2]·28H2O, and Cs16[(H2Si4W36Nb12O156)Cd(H2O)2]·75H2O involving [SiNb3W9O40]7− fundamental building unit, have been synthesized, which all show photocatalytic hydrogen evolution activities. Furthermore, molecules 1, 2, and 3 are stable in the photocatalytic hydrogen evolution system. The embedding transition-metal cations into Nb/W mixed-addendum POMs can improve the photocatalytic H2 evolution activity.

Nanostructured molybdenum disulfide (MoS2) is successfully embedded in the N-doped porous carbon to form micro-sized MoS2/N-C particles via a simple one-pot solution reaction. Yolk, a biomass carbon source with rich nitrogen and oxygen, makes a success to the heteroatom self-doping. The obtained N-doped porous carbon coating layers largely improve the conductivity and electrochemical activity. Moreover, the unique structure of MoS2 nanodots embedded in the porous carbon effectively combines the advantages of nanoscale MoS2 and micron scale N-doped C, which addresses the issues of MoS2 in lithium ion batteries (e.g., poor conductivity, sulfur loss and easy conglomeration). Interestingly, MoS2/N-C composite shows the first discharge/charge capacities of 1002 and 724 mAh g−1 at 0.1 A g−1 and stabilizes around 805 mAh g−1 after 100 cycles. Especially, it still remains at 630 mAh g−1 even under 0.5 A g−1 after 500 cycles, exhibiting excellent lithium ion (Li+) storage and cycle-to-cycle durability. This desired performance of MoS2/N-C is mainly resulted from the unique embedded structure, which effectively improves ion/electron transportation, ensures high sulfur reservation and prevents the conglomeration or accumulation during lithiation/delithiation reaction.

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 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.