Boosting the oxygen reduction activity of non-metallic catalysts via geometric and electronic engineering through nitrogen and chlorine dual-doping.

The development of heteroatom dual-doped porous carbon frameworks with uniform doping is highly desirable for achieving highly efficient oxygen reduction reaction (ORR) activity, due to their tunable chemical and electronic structures. Herein, porous covalent triazine-based frameworks (CTFs) incorporating nitrogen/chorine dual-doped porous carbon networks were fabricated by selecting 1,3-bis(4-cyanophenyl) imidazolium chloride as a building block, in a facile and controllable way via a bottom-up strategy. The resulting nitrogen/chorine dual-doped catalyst CCTF-700 exhibits excellent ORR performance with a more positive onset and half-wave potential (0.85 V vs. RHE), higher diffusion-limited current density and significantly improved stability in comparison with the benchmark commercial 20 wt% Pt/C catalyst. It is worth mentioning that CCTF-700 shows one of the best ORR performances among all the reported metal-free electrocatalysts under alkaline conditions. This work paves the way for a controllable and reliable strategy to craft highly efficient heteroatom dual-doped carbon catalysts for energy conversion.

Promoting the Photoelectrochemical Properties of BiVO4 Photoanode via Dual Modification with CdS Nanoparticles and NiFe-LDH Nanosheets.

Bismuth vanadate (BiVO4) has long been considered a promising photoanode material for photoelectrochemical (PEC) water splitting. Despite its potential, significant challenges such as slow surface water evolution reaction (OER) kinetics, poor carrier mobility, and rapid charge recombination limit its application. To address these issues, a triadic photoanode has been fabricated by sequentially depositing CdS nanoparticles and NiFe-layered double hydroxide (NiFe-LDH) nanosheets onto BiVO4, creating a NiFe-LDH/CdS/BiVO4 composite. This newly engineered photoanode demonstrates a photocurrent density of 3.1 mA cm-2 at 1.23 V vs. RHE in 0.1 M KOH under AM 1.5 G illumination, outperforming the singular BiVO4 photoanode by a factor of 5.8 and the binary CdS/BiVO4 and NiFe-LDH/BiVO4 photoanodes by factors of 4.9 and 4.3, respectively. Furthermore, it exhibits significantly higher applied bias photon-to-current efficiency (ABPE) and incident photon-to-current efficiency (ICPE) compared to pristine BiVO4 and its binary counterparts. This enhancement in PEC performance is ascribed to the formation of a CdS/BiVO4 heterojunction and the presence of a NiFe-LDH OER co-catalyst, which synergistically facilitate charge separation and transfer efficiencies. The findings suggest that dual modification of BiVO4 with CdS and NiFe-LDH is a promising approach to enhance the efficiency of photoanodes for PEC water splitting.

Iodine-doped g-C3N4 modified zinc titanate electron transporting layer for highly efficient perovskite solar cells.

The development of excellent ternary metal oxides as electron transporting layers (ETLs) is highly challenging for perovskite solar cells (PSCs). In this study, ZnTiO3 (ZTO) nanoparticles are synthesized via a facile sol-gel method, and used as an ETL in PSCs. Furthermore, for the first time, iodine-doped g-C3N4 (ICN) is introduced into ZnTiO3-based ETL as additive via a glass-assisted annealing route. Characterizations demonstrate that the ZnTiO3-based ETL with the addition of ICN will enhance the PCE, which is attributed to the improved crystalline quality and more favorable energy level alignment. Moreover, the existence of ICN will strengthen the interfacial cohesion between perovskite layer and ETL as well as retard the perovskite crystals from decomposing, leading to the high quality capping light-harvesting layer upon ICN-modified ZnTiO3 (ZTO-ICN) film. Consequently, a champion device fabricated with ZTO-ICN ETL achieves a maximum PCE of 19.17 % with an open circuit voltage (Voc) of 1.012 V, a short-circuit current density (Jsc) of 26.32 mA cm-2 and a fill factor (FF) of 0.720 under AM 1.5 G sunlight (100 mW cm-2).

Interfacial Assemble of Prussian Blue Analog to Access Hierarchical FeNi (oxy)-Hydroxide Nanosheets for Electrocatalytic Water Splitting.

Developing facile methods for the synthesis of active and stable electrocatalysts is vitally important to realize overall water splitting. Here, we demonstrate a practical method to obtain FeNiOOH nanosheets on nickel foam (NF) as bifunctional electrocatalyst by growing a FeCo Prussian blue analog with further in situ oxidation under ambient conditions. The binder-free, self-standing FeNiOOH/NF electrode with hierarchical nanostructures requires low overpotentials of 260 mV and 240 mV at a current density of 50 mA cm-2 for oxygen evolution reaction and hydrogen evolution reaction, respectively, in 1.0 M KOH solution. Therefore, an alkaline water electrolyzer constructed by bifunctional FeNiOOH/NF electrode as both anode and cathode delivers 50 mA cm-2 under a cell voltage of 1.74 V with remarkable stability, which outperforms the IrO2-Pt/C-based electrolyzer. The excellent performance could be ascribed to the superior FeNiOOH intrinsic activity and the hierarchical structure. This work provides a cost-efficient surface engineering method to obtain binder-free, self-standing bifunctional electrocatalyst on commercial NF, which could be further extended to other energy and environment applications.

Approach toward Iron(II) Coordination Polymers Based on Chain Motifs with Thiolate or Mixed Thiolate/Carboxylate Bridges: Structures and Magnetic Properties.

The search for iron-sulfur-based coordination polymers (CPs) has become an attractive field in recent years. Here we demonstrate how it is possible to synthesize new iron-sulfur-based CPs by solvothermal reactions of [CpFe(CO)2]2 (Cp = cyclopentadienyl) with two positional isomeric ligands 6-mercaptonicotinic acid (6-H2mna) and 2-mercaptoisonicotinic acid (2-H2mina) in different mixed-solvent systems. The reactions afforded, in moderate yields, a variety of desired CPs, namely, [Fe(6-Hmna)2] (1), [Fe3(6-Hmna)2(6-mna)2] (2), [Fe2(6-mna)2]·H2O (3), and [Fe(2 mina)(H2O)] (4 and 5). The structures of these compounds have been characterized by single-crystal X-ray diffraction, which reveals that they all contain 1D chain motifs of iron held together in different ways by thiolate or mixed thiolate/carboxylate bridges. These chains are further connected through the ligand backbones to form 3D networks of 1-3 and 5 and a 2D sheet of 4. Moreover, magnetic investigations indicate that both 1 and 4 display canted antiferromagnetic behavior with weak ferromagnetism, while 2 and 5 possess short-range antiferromagnetic order at ∼20 K. CP 3 exhibits paramagnetic behavior down to 2 K with strong spin frustration.

Ytterbium-Doped CsPbCl3 Quantum Cutters for Near-Infrared Light-Emitting Diodes.

Exploring highly efficient near-infrared (NIR) emitting materials is desirable for the advancement of next-generation smart NIR light sources. Different from most reported Cr3+-doped emitters with far-red emissions, Yb3+-activated phosphors are expected to yield pure NIR (∼1000 nm) light. Herein, a new hot-injection route using all metal-oleate salts to fabricate Yb3+-doped CsPbCl3 perovskite nanocrystals (PeNCs) is reported for the first time, which produce PeNC-sensitized Yb3+ NIR emission with photoluminescence quantum yields (PLQYs) higher than 100%. With the help of temperature-dependent PL spectra, femtosecond transient absorption spectra, and time-resolved PL spectra, it is evidenced that the in situ produced intrinsic shallow trap states in a CsPbCl3 host play a key role in facilitating the picosecond nonradiative cooperative energy transfer from PeNCs to two Yb3+ dopants simultaneously. Using the optimized Yb3+:CsPbCl3 quantum cutters, a phosphor-converted NIR light-emitting diode (pc-NIR-LED) is fabricated, exhibiting an external quantum efficiency of 2%@28 mA, a high NIR output irradiance of 112 mW/cm2@400 mA, and excellent long-term stability. Finally, the designed pc-NIR-LED is demonstrated to have great potential as an invisible night-vision light source.

A pentanuclear {Co5} cluster motif forming a capped breathing kagomé lattice.

A new pentanuclear {Co5} cluster motif is found to have a D3h oblate trigonal bipyramidal geometry, which is extended into a 3D triangle network, forming a unique capped breathing kagomé lattice. Magnetic results confirmed a paramagnetism down to 2 K, accompanying the disappearance of two-thirds of the spin moment at low-temperature and the appearance of a 1/5 magnetization plateau.

A novel series of giant cobalt-calixarene macrocycles: ring-expansion and modulation of pore apertures through recrystallization.

The design and synthesis of metallomacrocycles can be quite challenging because the assemblies of such molecular cycles are difficult to control and the products are usually unpredictable. In this work, a novel series of metallomacrocycles, denoted as {Co30-A}, {Co30-B} and {Co32-A} have been synthesized via self-assembly of p-tert-butylthiacalix[4]arene (H4TC4A) and 3,5-pyrazoledicarboxylic acid (H3pdc) with Co2+ ions under solvothermal conditions. Recrystallization of {Co32-A} under different conditions was found to form {Co32-B} and {Co32-C} that have a similar ring structure to that of {Co32-A} but have different molecular packing modes in the lattices, as well as a 40-membered ring {Co40}. These complexes represent the highest-nuclearity metallocalixarene coordination wheels reported to date. Crystallographic studies indicate that all these metallomacrocycles feature wheel-like structures with apertures varing from 11.4 to 20.3 Å. It is noteworthy that {Co32-A} exhibited good efficiency in removing RhB even at low initial concentration (10 ppm) and also excellent adsorption selectivity towards RhB over Na2Fl (RhB = Rhodamine B, Na2Fl = disodium fluorescein). This work not only makes a breakthrough in the synthesis of metallocalixarene macrocycles with high nuclearity and large apertures, but also provides a simple recrystallization approach to realize the ring-expansion and regulation of molecular packing modes of the metallomacrocycles.

In situ synthesis of g-C3N4 by glass-assisted annealing route to boost the efficiency of perovskite solar cells.

TiO2-based electron transport layers (ETLs) show tremendous advantages in constructing efficient perovskite solar cells (PSCs), but the power conversion efficiency (PCE) needs further improvements. Thus, in this study, graphitic carbon nitride (g-C3N4), a typical two-dimensional material, was synthesized in-situ and introduced into TiO2-based ETLs as an additive via a facile glass-assisted annealing route. The results demonstrated that the addition of g-C3N4 positively influenced the crystalline quality of the perovskite layers, as well as the conductivity and photovoltaic properties of the devices. Furthermore, favorable energy level alignment facilitated rapid migration of electrons and suppressed charge recombination at the interfaces. Consequently, the champion device fabricated using the g-C3N4-modified ETL achieved a maximum PCE of 20.46% owing to the remarkable improvement in the Voc, Jsc, and fill factor. The PCE is approximately 20% higher than that obtained for the pristine device, i.e., 17.18%.

Facile and scalable synthesis of Ti6Mn2 oxo-cluster nanocrystals with flower-like morphology and excellent photocatalytic properties.

Three new phenylphosphonate (PhPO3) and salicylate (Sal) substituted heterometallic titanium-oxo clusters (ST-M), namely [Ti6Mn2O4(OEt)4(PhPO3)2(Sal)6(EtOH)2] (ST-Mn), [Ti6Zn2O4(OEt)4(PhPO3)2(Sal)6(EtOH)2(H2O)2] (ST-Zn) and [Ti6Tb2O4(OiPr)4(PhPO3)2(Sal)6Cl2(iPrOH)2]·iPrOH (ST-Tb), were synthesized. The most impressive structural feature of these compounds is the calixarene-type carboxylate endpoint in the Ti6-oxo core, which can readily capture metal ions with different radii and coordination geometries, for example, Mn2+, Zn2+ and Tb3+ ions in this case, to generate neutral mixed-metal Ti6M2-oxo clusters. Flower-like ST-Mn (denoted as FST-Mn) nanocrystals formed by nanosheets can be facilely obtained in gram-scale quantities from a simple solution reaction using Triton X-100 as a conditioning agent. The catalytic activity of these materials was evaluated by photocatalytic degradation of rhodamine B (RhB), among which FST-Mn showed the highest catalytic activity. Under visible light, 93.0% of RhB (50 ppm, 100 mL) was decomposed within 30 min catalyzed by FST-Mn without adding hydrogen peroxide, which is quite preeminent among Ti based catalysts. The catalytic decomposition efficiency under the same experimental conditions was 80.0% for ST-Mn, 24.6% for ST-Zn and 17.6% for ST-Tb. Investigation of the degradation mechanism showed that h+ and ·OH were the dominant active species in the decomposition of RhB. Moreover, the reusability and stability of FST-Mn were also verified.

A stable LnMOF as a highly efficient and selective luminescent sensor for detecting malachite green in water and real samples.

A series of isostructural 3D lanthanide metal-organic frameworks (LnMOFs), with the formula n(H3O)[Ln(L)(H2O)] n ·nH2O (Ln = Gd 1, Eu 2 and Tb 3, H4L = 3,5,3',5'-oxytetrabenzoic acid), have been successfully synthesized by solvothermal reactions. Single-crystal X-ray diffraction analysis reveals that 1-3 are constructed from wave-like Ln-carboxylate chains which are further connected by the ligands to form 3D channel-type frameworks. Further experiments suggest that 3 is thermally stable up to 322 °C and exhibits outstanding chemical stability in aqueous solutions with the pH ranging from 3 to 11. Significantly, 3 can be utilized for the first time to detect malachite green (a synthetic antibiotic to cure saprolegniasis) in aqueous media even in the presence of other interfering antibiotics, with a high sensitivity (K sv = 8.33 × 104 M-1), low detection limit (DL = 0.25 µM) and good recyclability. On a more practical note, we found that the luminescence intensity of 3 showed almost no response to pH changes (pH 3-11), allowing steady sensing in real samples such as river water, simulated human serum and urine with satisfactory recoveries and RSD.

A highly hydrolytically stable lanthanide organic framework as a sensitive luminescent probe for DBP and chlorpyrifos detection.

Organic pollutants have attracted increasing attention due to their strong persistence and extensive diffusivity. Plasticizers (PAEs) and organophosphorus pesticides (OPs), as the vital part of organic pollutants, have made extensive damage to the environment with the rapid development of modern agriculture and industry. Therefore, we have, for the first time, carried out a quantitative analysis of the PAEs and OPs by fluorescence recognition. A series of isostructural lanthanide organic frameworks, [Ln(tftpa)1.5(2,2'-bpy)(H2O)] (Ln = Gd 1, Eu 2 and Tb 3, H2tftpa = tetrafluoroterephthalic acid), were hydrothermally synthesized, of which 3 exhibited excellent hydrolytic resistance to both boiling acidic and basic aqueous solutions. Moreover, luminescence investigations show that 3 can be used as a highly sensitive and recyclable luminescence sensor for the detection of DBP (di-n-butyl phthalate) in simulated seawater and chlorpyrifos in ethanol with the detection limits of 2.07 and 0.14 ppb, respectively.

A Multifunctional Nanocage-based MOF with Tri- and Tetranuclear Zinc Cluster Secondary Building Units.

A new Zn-cluster based MOF, [Zn21(BTC)11(µ3-OH)3(µ4-O)3(H2O)18]·21EtOH (1) (H3BTC = 1,3,5-benzenetricarboxylic acid), with two different types of cluster nodes has been successfully synthesized from Zn2+ and H3BTC under the solvothermal conditions. Single crystal X-ray diffraction studies reveal that 1 is a 3D trinodal (3,5,6)-c framework which features a large octahedral cage organized by nine Zn3O and nine Zn4O clusters SBUs and twenty-four triangular BTC3- linkers. The Eu3+/Tb3+-incorporated derivative of 1 with 0.251% Eu3+ and 0.269% Tb3+ exhibits tunable luminescence from yellow to white and then to blue-green by changing the excitation wavelength from 308 to 315 nm. Metal ion exchange with Cu2+ affords isomorphous Cu-based MOF with enhanced N2 and CO2 adsorption capacity. In addition, 1 can act as a selective luminescent sensor for Cu2+ and Al3+ ions.

A new approach to fabricate the Mn(ii)-based magnetic refrigerant through incorporation of a diamagnetic {LiO4} spacer.

A new 3D MOF [MnLi2(ip)2(H2O)2] (1) with a 1D heterometallic inorganic Mn(ii)-Li(i) chain is reported. With the assistance of diamagnetic {LiO4} connectors, which separate the paramagnetic Mn(ii) ions and act as magnetic spacers, very weak magnetic interactions were obtained. Remarkably, 1 showed a significant magnetocaloric effect (MCE) with a large entropy change value of 30.4 J kg-1 K-1 for ΔH = 8 T at 2 K.

A novel alb metalloring organic framework with a {Ni12Gd24} cage exhibiting a significant magnetocaloric effect.

With the aid of a bifunctional 6-mercaptonicotinic acid ligand, a novel {Ni12Gd24} cage-based (6, 12)-c alb-MROF that is assembled from a {Gd4(OH)4(COO)6} trigonal-prism building unit and a {Ni6S12} hexagonal-prism molecular building block has been synthesized for the first time. It exhibits a large MCE value of 29.86 J kg-1 K-1 for ΔH = 8 T at 2 K.

Magnetic Tuning of an Anionic CoII -MOF through Deionization of the Framework: Spin-Canting, Spin-Flop, and Easy-Plane Magnetic Anisotropy.

An anionic CoII -MOF, (Me2 NH2 )[Co3 (Me2 NH)3 (OH)(SDBA)3 ] (1) (H2 SDBA=4,4'-sulfonyldibenzoic acid) consisting of highly symmetric CoII3 (µ3 -OH) triangles exhibits spin-canting, spin-flop, and easy-plane magnetic anisotropy. Measurement on a single crystal shows that the ab plane of 1 is the easy magnetization plane. After structural modification through simultaneous removal of the coordinated dimethylamine (DMA) molecule at the Co center and the ionic groups DMA+ and OH- , the resulting neutral amorphous framework 2 displays an enhanced spin frustration effect. The deionization of 1 does not result in the collapse of the framework, showing the high stability of the backbone structure.

A Highly Energetic N-Rich Metal-Organic Framework as a New High-Energy-Density Material.

Metal-organic framework (MOF)-based energetic material [Cu3 (MA)2 (N3 )3 ] (1; MA=melamine) was synthesized and structurally characterized (47.55 % N). The structural analysis revealed the existence of unusual multiwalled tubular channels and interweaving of single and double helical units in 1. The standard molar enthalpy of formation was found to be 1788.73 kJ mol(-1) , which is the highest value among previously reported MOF-based energetic materials. The calculated detonation properties showed that 1 can be used as a potential explosive. Sensitivity tests revealed that 1 is insensitive and thus can function as a high-energy-density material with a favorable level of safety.

Microporous Lanthanide Metal-Organic Frameworks with Multiple 1D Channels: Tunable Colors, White-Light Emission, and Luminescent Sensing for Iron(II) and Iron(III).

A new series of isostructural lanthanide-based metal-organic frameworks, [H3 O][HN(CH3 )3 ]2 [Ln3 L6 ] (Ln=Gd (1), Eu (2), and Tb (3); H2 L=1,3-benzenedicarboxylic acid), was prepared under solvothermal conditions. Single-crystal XRD studies reveal that these compounds are 3D microporous frameworks with 1D channels distributed in four different directions. The 1D channels contain protonated water molecules and trimethylammonium cations, which can be partially exchanged with different metal ions. Notably, these compounds do not contain any coordinated solvent molecules because the coordination sphere of the Ln3+ ion is fully occupied by chelating and bridging carboxylate oxygen atoms. Tunable colors and white-light emission can be achieved by encapsulating different molar ratios of Eu3+ and Tb3+ ions in the Gd framework through cation exchange. In addition, the Eu framework can act as a sensitive and selective luminescence sensor for both Fe2+ and Fe3+ .

Chiral template induced homochiral MOFs built from achiral components: SHG enhancement and enantioselective sensing of chiral alkamines by ion-exchange.

A pair of chiral template induced anionic homochiral frameworks constructed from achiral components has been synthesized. Ion-exchange of counter cations with polar or chiral organic cations enhances the SHG efficiency of the frameworks. The enantioselective sensing of chiral alkamines can be achieved by the SHG response.

Interpreted Recognition Process: A Highly Sensitive and Selective Luminescence Chemosensor.

A luminescence-sensing process based on coordination compound [H2 N(CH3 )2 ]3 [Tb(dipic)3 ] was developed. It shows fast response (within 1 min), high selectivity, and is ultrasensitive to detect Fe(3+) or Cr(3+) in aqueous solution and living cells (KSV values are calculated to be 3.6×10(4)  L mol(-1) for Fe(3+) and 1.9×10(4)  L mol(-1) for Cr(3+) ). The whole recognition process has been witnessed through electrospray ionization mass spectrometry (ESI-MS) analysis, and the ligand-transfer-induced luminescence-quenching mechanism is interpreted. This work contributes to extend the potential applications of lanthanide coordination compounds (LnCCs) in the fields of biological and environmental technologies.