D-electron Configuration Research Articles

Elevating Nonlinear Optical Response Through D-Electron Modulation in Metal-Organic Frameworks.

Electronic structure and excited state behavior is of pronounced influence on regulation of nonlinear optical (NLO) response. Herein, a serials of transition metal ions bearing different d-electron numbers were in situ coordinated within porphyrinic metal-organic frameworks (MOFs), creating NLO-responsive M-metal (metal=Fe, Co, Ni, Cu, and Zn) frameworks. It demonstrated that the NLO properties can be optimized with the increased occupancy of the d-shell, which enhances the degree of delocalization. Specifically, the full-filled (d10) electron configuration of Zn2+ stabilizes the electronic structure, combination with π-π* local excitation character of M-Zn, promoting charge transfer process and resulting in outstanding NLO properties. Moreover, parameters related to the nonlinear process (β, n2, Imχ(3), Reχ(3) and χ(3)) of M-Zn are calculated to be higher than those of other materials, consistent with theoretical calculations. This work paves the way for NLO modulation based on electronic analysis and provides a promising approach for constructing high-performance NLO materials.

Fabrication of a novel mixed-valent copper-based coordination polymer as a fluorescent sensor for selective and efficient detection of multiple analytes

A novel three-dimensional fluorescent mixed-valent copper-based coordination polymer (CP), namely {[CuICuII4(triazol)6(bpta)2]Cl}n (Cu-CP), was synthesized hydrothermally in the presence of Cu(II) ion, 2,4,6-tri(1H-1,2,4-triazol-1-yl)-1,3,5-triazine (TTT), and 2,2′,4,4′-biphenyltetracarboxylic acid (H4bpta). The structure of the Cu-CP was studied using single-crystal X-ray diffraction (SCXRD) and powder X-ray diffraction (PXRD). Interestingly, the crystallographic data revealed that a part of Cu(II) ions were reduced in situ to Cu(I) ions as well as the nitrogen-containing ligand TTT was converted to triazol, which possessed excellent fluorescence characteristics as a transition metal ion with a d10 electronic configuration, prompting further investigation into the fluorescence sensing properties of Cu-CP. The results confirmed that Cu-CP exhibited excellent fluorescence performance which an outstanding candidate as a fluorescence sensor for Fe3+, Cr2O72−, CrO42−, MnO4− and nitrobenzene (NB), with a low limit of detection. For ethylene glycol (EG) detection, Cu-CP showed high-efficiency fluorescence enhancement across a range of temperatures. The underlying mechanism of fluorescence enhancement was investigated through comprehensive experimental studies.

Unraveling the Fast Ionic Conduction in NASICON‐Type Materials

AbstractNa Superionic Conductor (NASICON) materials stand out as an important class of ionic conductors, offering high ionic conductivity and notable electrochemical stability for applications such as solid electrolytes. While advances through compositional engineering have been made to enhance the ionic conductivity of NASICONs, the fundamental mechanisms underlying their superionic conducting behavior remain unresolved. In this study, the interplay between local and global factors—specifically, bottleneck volume and Na site ordering— that influence ionic conduction within the NASICON framework is elucidated. Analysis of reported ionic conductivity data indicates that optimal bottleneck volumes exceed 3.7 Å3, adjustable through the choice of metal cations and polyanions. Additionally, the findings imply that weaker Na site ordering, which enhances ionic conduction, can be induced by increasing the Na content, selecting metal cations with a d0 electron configuration, or mixing elements at the cation or polyanion sites. Moreover, it is proposed that the predominant diffusion mechanism can shift between occupancy‐conserved hopping (OCH), occurring under conditions of strong Na site ordering, and single‐ion hopping (SIH), which becomes possible when site ordering is minimal. These insights offer strategic guidelines for designing NASICONs with superionic conductivity, promoting the development of solid electrolytes for safer and more energy‐dense all‐solid‐state batteries.

Activating d10 electronic configuration to regulate p-band centers as efficient active sites for solar energy conversion into H2 by surface atomic arrangement

Relationship between the activity for photocatalytic H2O overall splitting (HOS) and the electron occupancy on d orbits of the active component in photocatalysts shows volcanic diagram, and specially the d10 electronic configuration in valley bottom exhibits inert activity, which seriously fetters the development of catalytic materials with great potentials. Herein, In d10 electronic configuration of In2O3 was activated by phosphorus atoms replacing its lattice oxygen to regulate the collocation of the ascended In 5p-band (In ɛ5p) and descended O 2p-band (O ɛ2p) centers as efficient active sites for chemisorption to *OH and *H during forward HOS, respectively, along with a declined In 4d-band center (In ɛ4d) to inhibit its backward reaction. A stable STH efficiency of 2.23% under AM 1.5 G irradiation at 65 °C has been obtained over the activated d10 electronic configuration with a lowered activation energy for H2 evolution, verified by femtosecond transient absorption spectroscopy, in situ diffuse reflectance infrared Fourier transform spectroscopy and theoretical calculations of dynamics. These findings devote to activating d10 electronic configuration for resolving the reaction energy barrier and dynamical bottleneck of forward HOS, which expands the exploration of high-efficiency catalytic materials.

Regulating electronic structure of anionic oxygen by Ti4+ doping to stabilize layered Li-rich oxide cathodes for Li-ion batteries

Abstract Layered Li-rich oxide cathodes enable to activate lattice oxygen anions redox in the charge compensation process and provide superior high specific capacity over 250 mAh g−1 due to their unique configuration, and thus attracting great attentions as promising cathode candidates for Li-ion batteries. However, how to better stabilize the bulk lattice oxygen framework and surface structure, and slow down the release of oxygen, is still major bottleneck to develop high performance Li-rich materials. Transition metal ions with outer d0 electronic configuration have distortable configuration, which can accommodate the local structure and chemical environment of the material, and then improve structural stability. Herein this work, the d0 transition metal Ti4+ is used as doping element to improve the chemical and structural stability, capacity retention and lithium ion diffusion kinetics of Li-rich material. The role of Ti in the material modification is revealed through synchrotron-based soft x-ray absorption spectroscopy, XRD, XPS and electrochemical tests. The improvement in structural stability can be attributed to that Ti doping can adjust the hybridization of O2p and TM3d to regulate the local electronic structure of both bulk lattice oxygen and surface oxygen vacancies. It is hoped that this work should shed light on the development of high-performance cathode materials for Li-ion Batteries.

Shining New Light on Biological Systems: Luminescent Transition Metal Complexes for Bioimaging and Biosensing Applications.

Luminescence imaging is a powerful and versatile technique for investigating cell physiology and pathology in living systems, making significant contributions to life science research and clinical diagnosis. In recent years, luminescent transition metal complexes have gained significant attention for diagnostic and therapeutic applications due to their unique photophysical and photochemical properties. In this Review, we provide a comprehensive overview of the recent development of luminescent transition metal complexes for bioimaging and biosensing applications, with a focus on transition metal centers with a d6, d8, and d10 electronic configuration. We elucidate the structure-property relationships of luminescent transition metal complexes, exploring how their structural characteristics can be manipulated to control their biological behavior such as cellular uptake, localization, biocompatibility, pharmacokinetics, and biodistribution. Furthermore, we introduce the various design strategies that leverage the interesting photophysical properties of luminescent transition metal complexes for a wide variety of biological applications, including autofluorescence-free imaging, multimodal imaging, organelle imaging, biological sensing, microenvironment monitoring, bioorthogonal labeling, bacterial imaging, and cell viability assessment. Finally, we provide insights into the challenges and perspectives of luminescent transition metal complexes for bioimaging and biosensing applications, as well as their use in disease diagnosis and treatment evaluation.

Self-templated formation of ZnNC microtube with high oxygen reduction reaction overpotential for Zn-based catalyst

The synthesis of hollow morphologies without employing templates and addressing the high overpotential of the oxygen reduction reaction in Zn-N4-C-based materials poses a significant challenge. In this study, we present a straightforward yet robust approach based on a self-templated metal-organic framework (MOF-based) to synthesize ZnNC microtubes and explore the reason behind its high oxygen reduction (ORR) overpotential through density functional theory (DFT) calculation. ZnNC microtubes, benefiting from the abundant Zn-N4 active sites, hierarchical porosity, and a reasonable degree of graphitization, exhibited superior ORR activity and methanol tolerance compared to the traditional precious Pt/C catalyst. On the other hand, DFT calculation shows that Zn exhibits a d10 electronic configuration and diamagnetic nature in Zn-N4 moieties confirmed by the partial density of state (PDOS), hence the main reason behind the high ORR overpotential. This study provides a novel roadmap for further engineering efforts to achieve an ideal ORR catalyst in Zn-based materials.

Spotlight on Zinc: Exploring the Visible Light Responsiveness of Zinc Complexes.

Group 12 element zinc(II)-based d10 complexes have long been known for their inherent colorlessness, which has limited their applications in visible light-driven photophysical and photochemical applications, despite the attractiveness of inexpensive and low-toxicity zinc metal. Based on precedents with nickel(0) and copper(I) complexes, which also adopt the d10 electronic configuration, achieving a visible light response from zinc(II) complexes seems feasible; however, investigations and proactive design strategies specifically tailored to zinc remain lacking. In this context, the present invited concept paper highlights zinc's potential for visible light responsiveness and evaluates how molecular designs can achieve this capability. After delineating the differences between zinc and other d10 metal centers, we review recent developments in zinc complexes that exhibit visible light absorption and compare these complexes with previously reported colorless complexes to identify key distinctions. This study provides critical insights into the molecular design guidelines that are pivotal for harnessing the emerging potential of zinc for visible light responses.

Stabilizing NASICON-type Na4MnCr(PO4)3 by Ti-substitution toward a high-voltage cathode material for sodium ion batteries

The sodium superionic conductor Na4MnCr(PO4)3 gains increasing attention owing to its three-dimensional structure and the three-electron reaction. However, rapid structure degradation during cycling is the major challenge for its practical application. Herein, Ti4+ is utilized to replace a portion of Mn2+ in Na4MnCr(PO4)3. The low redox voltage and d0 electronic configuration of the Ti4+ ions are helpful to suppress the structure alteration and improve electronic conduction. Consequently, the as-prepared Na3.4Mn0.7Ti0.3Cr(PO4)3/C cathode exhibits a remarkable good 91.0% capacity retention after 500 cycles at 10C rate, with exceptional rate capacities of 99.5 mAh g−1 and 81.0 mAh g−1 at 5C and 10C rate, respectively. Furthermore, based on ≈2.86-electron reactions involving Mn2+/Mn3+ (3.5 V), Mn3+/Mn4+ (4.1 V), Cr3+/Cr4+ (4.3 V), and Ti3+/Ti4+ (2.1 V), the material can provide an energy density of approximately 541.6 Wh kg−1, slightly surpassing that of Na4MnCr(PO4)3. Ex-situ XRD investigation further elucidates that throughout the entire charge–discharge process, the Ti-substituted material experiences highly reversible solid-solution and two-phase reactions. Additionally, Ti substitution can greatly promote the interfacial charge transfer of the material and suppress the decomposition of the electrolyte during cycling. This work might open a new insight for designing sodium-ion battery cathode materials with good cycling stability and high energy density.

Mechanochemical Synthesis of Chromium(III) Complexes Containing Bidentate PN and Tridentate P-NH-P and P-NH-P' Ligands.

Chromium(III) complexes bearing bidentate {NH2(CH2)2PPh2: PN, (S,S)-[NH2(CHPh)2PPh2]: P'N} and tridentate [Ph2P(CH2)2N(H)(CH2)2PPh2: P-NH-P, (S,S)-(iPr)2PCH2CH2N(H)CH(Ph)CH(Ph)PPh2: P-NH-P'] ligands have been synthesized using a mechanochemical approach. The complexes {cis-[Cr(PN)Cl2]Cl (1), cis-[Cr(P'N)Cl2]Cl (2), mer-Cr(P-NH-P)Cl3 (3), and mer-Cr(P-NH-P')Cl3 (4)} were obtained in high yield (95-97%) via the grinding of the respective ligands andthe solid Cr(III) ion precursor [CrCl3(THF)3] with the aid of a pestle and mortar, followed by recrystallization in acetonitrile. The isolated complexes are high spin. A single-crystal X-ray diffraction study of 2 revealed a cationic chromium complex with two P'N ligands in a cis configuration with P' trans to P' with chloride as the counteranion. The X-ray study of 4 shows a neutral Cr(III) complex with the P-NH-P' ligand in a mer configuration. The difference in molecular structures and bulkiness of the ligands influence the electronic, magnetic, and electrochemical properties of the complexes as exhibited by the bathochromic shifts in the electronic absorption peaks of the complexes and the relative increase in the magnetic moment of 3 (4.19 μβ) and 4 (4.15 μβ) above the spin only value (3.88 μβ) for a d3 electronic configuration. Complexes 1-4 were found to be inactive in the hydrogenation of an aldimine [(E)-1-(4-fluorophenyl)-N-phenylmethanimine] under a variety of activating conditions. The addition of magnesium and trimethylsilyl chloride in THF did cause hydrogenation at room temperature, but this occurred even in the absence of the chromium complex. The hydrogen in the amine product came from the THF solvent in this novel reaction, as determined by deuterium incorporation into the product when deuterated THF was used.

Polyoxometalate-derived bi-functional crystalline/amorphous interfaces with optimized d-electron configuration for efficient self-powered hydrazine-seawater splitting

Hydrazine-assisted water electrolysis is a promising energy-efficient strategy for hydrogen production. Nonetheless, developing high-performance bi-functional electrocatalysts towards both hydrogen evolution reaction (HER) and hydrazine oxidation reaction (HzOR) remains great challenges, especially for hydrazine-seawater splitting. Herein, we report a polyoxometalate-assisted in-situ synthesis protocol for constructing bi-functional crystalline/amorphous Pt/MoO3-x interfaces toward both efficient HER and HzOR. The polyoxometalate-derived crystalline/amorphous Pt/MoO3-x interfaces deliver working potentials of only –23 and −41 mV at 10 mA cm−2 for HER and HzOR in seawater electrolyte, respectively. Meanwhile, ultrahigh mass activities of 38.39 AmgPt-1 for HER at −100 mV potential and 23.84 AmgPt-1 for HzOR at 50 mV potential are also achieved, over 30.2 and 52.9 times higher than those of commercial Pt/C. As bi-functional electrocatalysts for overall hydrazine-seawater splitting, the electrolyzer requires a cell voltage of only 55/238 mV at 10/100 mA cm−2, 1.584/1.543 V lower than that of the seawater splitting system. Moreover, a proof-of-concept self-powered hydrazine-seawater electrolysis system driven by direct hydrazine fuel cell is further demonstrated, which achieves a hydrogen production rate of 0.29 mL cm−2min−1. DFT calculations verify that, the crystalline/amorphous interfaces endow Pt/MoO3-x an optimized d-electron configuration with favorable H* adsorption and promoted dehydrogenation kinetics of *N2H4 to *N2H3 in the potential-determining step. This work provides a novel strategy and inspiration toward the design of efficient bi-functional electrocatalysts for hydrazine-assisted hydrogen production from seawater.

Vacancy-Enhanced Sb-N4 Sites for the Oxygen Reduction Reaction and Zn-Air Battery.

With the advantages of a Fenton-inactive characteristic and unique p electrons that can hybridize with O2 molecules, p-block metal-based single-atom catalysts (SACs) for the oxygen reduction reaction (ORR) have tremendous potential. Nevertheless, their undesirable intrinsic activity caused by the closed d10 electronic configuration remains a major challenge. Herein, an Sb-based SAC featuring carbon vacancy-enhanced Sb-N4 active centers, corroborated by the results of high-angle annular dark-field scanning transmission electron microscopy and X-ray absorption fine structure, has been developed for an incredibly effective ORR. The obtained SbSA-N-C demonstrates a positive half-wave potential of 0.905 V and excellent structural stability in alkaline environments. Density functional theory calculations reveal that the carbon vacancies weaken the adsorption between Sb atoms and the OH* intermediate, thus promoting the ORR performance. Practically, the SbSA-N-C-based Zn-air batteries achieve impressive outcomes, such as a high power density of 181 mW cm-2, showing great potential in real-world applications.

Bimetal‐bridging Nitrogen Coordination in Carbon‐based Electrocatalysts for pH‐universal Oxygen Reduction

AbstractElectrocatalysts with atomically dispersed metal sites (e.g., metal‐nitrogen‐carbon) have been deemed as promising alternatives for noble‐metal catalysts in couples of electrocatalytic reactions. However, the modulation of such atomic sites and the understanding of their interactions are still highly challenging. Herein, we propose a unique supermolecule assembly‐profile coating strategy to prepare a series of diatomic electrocatalysts by profile coating of eight Prussian blue analogues (PBAs) on supramolecular supports respectively as bimetallic sources. The detailed microstructure analysis revealed that the metal‐nitrogen‐carbon sites with four‐ (Zn−N4) and five‐coordination (Fe−N5) via the nitrogen coordination are similar to the cytochrome c oxidases. For promising electrocatalysis, such unique microstructure is able to activate oxygen molecules due to nitrogen‐bonding coordination with bimetal sites, thus leading to efficient four‐electron oxygen reduction in alkaline, neutral, and acid electrolytes. Especially, zinc group elements (e.g., Zn and Cd) with d10 electron configuration would significantly boost the nitrogen‐bonding coordination with bimetal sites to enhance electrocatalytic activity. The proof‐of‐concept for the general synthesis of advanced electrocatalysts with controllable bimetal active sites and the mechanistic understanding will promote the promising electrocatalysis by applying the similar principles.

Bimetal-bridging Nitrogen Coordination in Carbon-based Electrocatalysts for pH-universal Oxygen Reduction.

Electrocatalysts with atomically dispersed metal sites (e.g., metal-nitrogen-carbon) have been deemed as promising alternatives for noble-metal catalysts in couples of electrocatalytic reactions. However, the modulation of such atomic sites and the understanding of their interactions are still highly challenging. Herein, we propose a unique supermolecule assembly-profile coating strategy to prepare a series of diatomic electrocatalysts by profile coating of eight Prussian blue analogues (PBAs) on supramolecular supports respectively as bimetallic sources. The detailed microstructure analysis revealed that the metal-nitrogen-carbon sites with four- (Zn-N4 ) and five-coordination (Fe-N5 ) via the nitrogen coordination are similar to the cytochrome c oxidases. For promising electrocatalysis, such unique microstructure is able to activate oxygen molecules due to nitrogen-bonding coordination with bimetal sites, thus leading to efficient four-electron oxygen reduction in alkaline, neutral, and acid electrolytes. Especially, zinc group elements (e.g., Zn and Cd) with d10 electron configuration would significantly boost the nitrogen-bonding coordination with bimetal sites to enhance electrocatalytic activity. The proof-of-concept for the general synthesis of advanced electrocatalysts with controllable bimetal active sites and the mechanistic understanding will promote the promising electrocatalysis by applying the similar principles.

Enhanced thermally stable performance of Pr3+-doped vanadate phosphor by inhibiting the intervalence charge transfer quenching channel.

Praseodymium (Pr3+) ion and the transition metal vanadium (V5+) ion with d0 electronic configuration can form an intervalence charge transfer (IVCT) band, which can function both as a compensatory channel for its red emission and as a quenching channel, thus affecting the luminescence thermal stability of the phosphors. Research studies reveal that the emission of Pr3+ in the YVO4 matrix can be quenched by the IVCT mechanism, thereby limiting the application of phosphors. As such, the present contribution is based on the solid solution replacement strategy to inhibit the constitutent of the IVCT quenching channel and thus improve thermal stability. Therefore, phosphonium (P5+) with a valence state matching V5+ and a similar ion radius was selected for the V/P substitution. It lacks a d0 electron configuration, preventing the formation of an IVCT band with Pr3+ and thereby inhibiting the construction of the quenching channels to enhance thermal stability. While the empirical formula of IVCT indicates a decrease in the IVCT energy level from 3.32438 to 3.06251 eV upon the introduction of P5+, the PLE spectra demonstrate a sharp reduction in IVCT intensity, i.e., weakening of the quenching channel. The thermal stability of the phosphors at different excitation locations was enhanced with the rise of P5+ concentration. When excited at the 3P2 level, the Y0.995PO4:0.5%Pr3+ phosphor demonstrated highly stable red emission from 303 to 523 K, with a luminescence integrated intensity ranging from 95.5% to 105.3% compared to that at 303 K. This research provides a novel approach for inhibiting the IVCT quenching channel and broadens the commercial value of YVO4:Pr3+ phosphor for various applications.

Structural modification of nickel tetra(thiocyano)corroles during electrochemical water oxidation.

In this study, we present two fully characterized nickel tetrathiocyanocorroles, representing a novel class of 3d-metallocorroles. These nickel(II) ions form square planar complexes, exhibiting a d8-electronic configuration. These anionic complexes are stabilized by the electron-withdrawing SCN groups on the bipyrrole unit of the corrole. The reduced aromaticity in these anionic nickel(II) corrole complexes is evidenced by single crystal X-ray diffraction (XRD) data and a markedly altered absorption profile, with stronger Q bands compared to Soret bands. Notably, the UV-Vis and electrochemical data exhibit significant differences from previously reported nickel(II) corrole radical cation and nickel(II) porphyrin complexes. While these electrochemical data bear a resemblance to those of the anionic nickel(II) corrole by Gross et al., the UV-Vis data show substantial distinctions. Additionally, we explore the utilization of nickel(II)-corrole@CC (where CC denotes carbon cloth) as an electrocatalyst for the oxygen evolution reaction (OER) in an alkaline medium. During electrochemical water oxidation, the molecular catalyst is partially converted to nickel (oxy)hydroxide, Ni(O)OH. The structure reveals the coexistence of the molecular complex and Ni(O)OH in the active catalyst, achieving a turnover frequency (TOF) of 3.32 × 10-2 s-1. The synergy between the homogeneous and heterogeneous phases improves the OER activity, providing more active sites and edge sites and enhancing interfacial charge transfer.

Molybdenum(VI) complexes of N, N′-bis isatin diamine Schiff base: Synthesis and characterization

Schiff base ligand of N, N′-bis isatin diamine was synthesized from various diamine and isatin through condensation reaction in 1:2 molar ratio. Mo(VI) complexes of isatin-diamines were synthesized by the reaction between the sodium molybdate dehydrate and N,N' bis isatin diamines with the reflux method. The synthesized ligand and complexes were characterized using spectroscopic techniques. The FT-IR band of azomethine group at 1600- 1610 cm-1 indicated the formation of the ligand. The UV-vis spectra clearly indicated that the prepared complex is a genuine Mo(VI) with d0 electronic configuration. The formation of a coordination bond was revealed by the downfield chemical shift of the complex in the NMR data as compared to the ligand. The UV results were corroborated by molar conductance data, which demonstrated their non-electrolytic character. The experimental evidence primarily supported the synthesis of both ligands and corresponding Mo(VI) complexes. Bangladesh J. Sci. Ind. Res. 58(4), 201-208, 2023

The mechanism of surface activation in sphalerite by metal ions with d10 electronic configurations: Experimental and DFT study

The activation mechanism of metal ions with d10 inert electronic configurations on sphalerite (ZnS) were studied by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray fluorescence (XRF), and X-ray photoelectron spectroscopy (XPS), combined with density functional theory (DFT). Flotation experiments showed that the addition of activators increased sphalerite recovery by 50–70 %. The XPS results indicated that these inert cations with d10 electronic configurations formed stable metal sulfides (Cu2S, CuS, Ag2S, CdS, and HgS) on the sphalerite surface. The FTIR results demonstrated that the activated sphalerite enhanced the adsorption stability of butyl xanthate on the sphalerite surface. DFT studies found that metal ion introduction reduced surface relaxation and decreased the band gap on the sphalerite surface, both of which increased butyl xanthate adsorption. Finally, it was suggested in this study that the energy required for the d10 to d9s1 electron transition and the polarization could be used to predict the potential sphalerite activator.

Synergistic Nitrogen Binding Sites in a Metal‐Organic Framework for Efficient N2/O2 Separation

AbstractPorous materials with d3 electronic configuration open metal sites have been proved to be effective adsorbents for N2 capture and N2/O2 separation. However, the reported materials remain challenging to address the trade‐off between adsorption capacity and selectivity. Herein, we report a robust MOF, MIL‐102Cr, that features two binding sites, can synergistically afford strong interactions for N2 capture. The synergistic adsorption site exhibits a benchmark Qst of 45.0 kJ mol−1 for N2 among the Cr‐based MOFs, a record‐high volumetric N2 uptake (31.38 cm3 cm−3), and highest N2/O2 selectivity (13.11) at 298 K and 1.0 bar. Breakthrough experiments reveal that MIL‐102Cr can efficiently capture N2 from a 79/21 N2/O2 mixture, providing a record 99.99 % pure O2 productivity of 0.75 mmol g−1. In situ infrared spectroscopy and computational modelling studies revealed that a synergistic adsorption effect by open Cr(III) and fluorine sites was accountable for the strong interactions between the MOF and N2.

Synergistic Nitrogen Binding Sites in a Metal-Organic Framework for Efficient N2 /O2 Separation.

Porous materials with d3 electronic configuration open metal sites have been proved to be effective adsorbents for N2 capture and N2 /O2 separation. However, the reported materials remain challenging to address the trade-off between adsorption capacity and selectivity. Herein, we report a robust MOF, MIL-102Cr, that features two binding sites, can synergistically afford strong interactions for N2 capture. The synergistic adsorption site exhibits a benchmark Qst of 45.0 kJ mol-1 for N2 among the Cr-based MOFs, a record-high volumetric N2 uptake (31.38 cm3 cm-3 ), and highest N2 /O2 selectivity (13.11) at 298 K and 1.0 bar. Breakthrough experiments reveal that MIL-102Cr can efficiently capture N2 from a 79/21 N2 /O2 mixture, providing a record 99.99 % pure O2 productivity of 0.75 mmol g-1 . In situ infrared spectroscopy and computational modelling studies revealed that a synergistic adsorption effect by open Cr(III) and fluorine sites was accountable for the strong interactions between the MOF and N2 .