Enhanced Propylene/Propane Separation via Aniline-Decorated ZIF-8 Membrane: Lattice Rigidity Adjustment and Adsorption Site Introduction.

Metal-organic framework (MOF)-based membranes excel in molecular separation, attracting significant research interest. The crystallographic microstructure and selective adsorption capacity of MOFs closely correlate with their gas separation performance. Here, aniline was added to the ZIF-8 synthesis in varying concentrations. Aniline, encapsulated within ZIF-8 cavities, interacts strongly with the 2-methylimidazole linker, resulting in both a shift in crystallographic phase from I_43m to Cm in Rietveld refinement of X-ray diffraction (XRD) patterns and the selective adsorption behavior between propylene and propane. Consequently, an aniline decorative ZIF-8 (Anix-ZIF-8) membrane was prepared using a fast current-driven synthesis method, which exhibits good propylene/propane separation selectivity of up to 85. Calculation of the interaction energy between aniline and the various crystallographic phases of ZIF-8 using density functional theory (DFT) further verifies that aniline not only promotes the formation of crystallographic Cm phase, but also enhances the adsorption selectivity of propylene over propane. Aniline modification effectively tunes the crystallographic microstructure of ZIF-8, thereby, improving molecular sieving capabilities.

Interface-Triggered Spin-Magnetic Effect in Rare Earth Intra-particle Heterostructured Nanoalloys for Boosting Hydrogen Evolution.

Rare earth (RE) elements are attractive for spin-magnetic modulation due to their unique 4f electron configuration and strong orbital couplings. Alloying RE with conventional 3d transition-metal (TM) is promising for the fabrication of advanced spin catalysts yet remains much difficulties in preparation, which leads to the mysteries of spin-magnetic effect between RE and 3d TM on catalysis. Here we define a solid-phase synthetic protocol for creating RE-3d TM-noble metal integrated intraparticle heterostructured nanoalloys (IHAs) with distinct Gd and Co interface within the entire Rh framework, denoted as RhCo-RhGd IHAs. They exhibit interface-triggered antiferromagnetic interaction, which can induce electron redistribution and regulate spin polarization. Theoretical calculations further reveal that active sites around the heterointerface with weakened spin polarization optimize the adsorption and dissociation of H2O, thus promoting alkaline hydrogen evolution catalysis. The RhCo-RhGd IHAs show a small overpotential of 11.3 mV at 10 mA cm-2, as well as remarkable long-term stability, far superior to previously reported Rh-based catalysts.

Isoreticular Metal-Organic Frameworks with Aromatic Pores and Dimethylammonium Cations Enable Separation of Light Hydrocarbons and Xenon/Krypton.

The separation of C2-C3 hydrocarbons from methane in natural gas and xenon/krypton purification are crucial yet challenging industrial processes. Herein, we report two isoreticular metal-organic frameworks, ZJU-89 and ZJU-90, featuring aromatic pore environments and dimethylammonium cations, that synergistically enhance the separation of these industrially relevant gas mixtures. ZJU-90 exhibits an exceptional separation performance, achieving C3H8/CH4 and C2H6/CH4 ideal adsorbed solution theory (IAST) selectivities of 1065 and 48, respectively, at ambient conditions, outperforming most reported adsorbent materials. Remarkably, ZJU-90 enables the recovery of >99.95% purity methane from a C3H8/C2H6/CH4 mixture in a single adsorption step. The material also demonstrates the efficient separation of xenon from krypton, even at low concentrations. The superior performance stems from the aromatic rings decorating the pore walls and the free dimethylammonium cations in the channels, which provide an ideal chemical environment for the selective binding of C2H6, C3H8, and Xe through multiple C-H···π interactions and van der Waals forces, as elucidated by theoretical calculations. This work highlights the power of reticular chemistry in designing materials with synergistic pore environments for efficient separations.

Lanthanide-Induced Ligand Effect to Regulate the Electronic Structure of Platinum-Lanthanide Nanoalloys for Efficient Methanol Oxidation.

The ligand effect in alloy catalysts is one of the decisive parameters of the catalytic performance. However, the strong interrelation between the ligand effect and the geometric effect of the active atom and its neighbors as well as the systematic alteration of the microenvironment of the active site makes the active mechanism unclear. Herein, Pt3Tm, Pt3Yb, and Pt3Lu with a cubic crystal system (Pm-3m) were selected. With the difference of Pt-Pt interatomic distance within 0.02 Å, we minimize the geometric effect to realize the disentanglement of the system. Through precise characterization, due to the low electronegativity of Ln (Ln = Tm, Yb, and Lu) and the ligand effect in the alloy, the electronic structure of Pt is continuously optimized, which improves the electrochemical methanol oxidation reaction (MOR) performance. The Ln electronegativity has a linear relationship with the MOR performance, and Pt3Yb/C achieves a high mass activity of up to 11.61 A mgPt-1, which is the highest value reported so far in Pt-based electrocatalysts. The results obtained in this study provide fundamental insights into the mechanism of ligand effects on the enhancement of electrochemical activity in rare-earth nanoalloys.

Dilute Pd-Ni Alloy through Low-temperature Pyrolysis for Enhanced Electrocatalytic Hydrogen Oxidation.

Designing highly active and cost-effective electrocatalysts for the alkaline hydrogen oxidation reaction (HOR) is critical for advancing anion-exchange membrane fuel cells (AEMFCs). While dilute metal alloys have demonstrated substantial potential in enhancing alkaline HOR performance, there has been limited exploration in terms of rational design, controllable synthesis, and mechanism study. Herein, we developed a series of dilute Pd-Ni alloys, denoted as x% Pd-Ni, based on a trace-Pd decorated Ni-based coordination polymer through a facile low-temperature pyrolysis approach. The x% Pd-Ni alloys exhibit efficient electrocatalytic activity for HOR in alkaline media. Notably, the optimal 0.5% Pd-Ni catalyst demonstrates high intrinsic activity with an exchange current density of 0.055 mA cm-2, surpassing that of many other alkaline HOR catalysts. The mechanism study reveals that the strong synergy between Pd single atoms (SAs)/Pd dimer and Ni substrate can modulate the binding strength of proton (H)/hydroxyl (OH), thereby significantly reducing the activation energy barrier of a decisive reaction step. This work offers new insights into designing advanced dilute metal or single-atom-alloys (SAAs) for alkaline HOR and potentially other energy conversion processes.

Interfacial Accumulation and Stability Enhancement Effects Triggered by Built-in Electric Field of SnO2/LaOCl Nanofibers Boost Carbon Dioxide Electroreduction.

Constructing a built-in interfacial electric field (BIEF) is an effective approach to enhance the electrocatalysts performance, but it has been rarely demonstrated for electrochemical carbon dioxide reduction reaction (CO2RR) to date. Herein, for the first time, SnO2/LaOCl nanofibers (NFs) with BIEF is created by electrospinning, exhibiting a high Faradaic efficiency (FE) of 100% C1 product (CO and HCOOH) at -0.9--1.1 V versus reversible hydrogen electrode (RHE) and a maximum FEHCOOH of 90.1% at -1.2 VRHE in H-cell, superior to the commercial SnO2 nanoparticles (NPs) and LaOCl NFs. SnO2/LaOCl NFs also exhibit outstanding stability, maintaining negligible activity degradation even after 10 h of electrolysis. Moreover, their current density and FEHCOOH are almost 400 mA cm-2 at -2.31 V and 83.4% in flow-cell. The satisfactory CO2RR performance of SnO2/LaOCl NFs with BIEF can be ascribed to tight interface of coupling SnO2 NPs and LaOCl NFs, which can induce charge redistribution, rich active sites, enhanced CO2 adsorption, as well as optimized Gibbs free energy of *OCHO. The work reveals that the BIEF will trigger interfacial accumulation and stability enhancement effects in promoting CO2RR activity and stability of SnO2-based materials, providing a novel approach to develop stable and efficient CO2RR electrocatalysts.

Dual cation-modified hierarchical nickel hydroxide nanosheet arrays as efficient and robust electrocatalysts for the urea oxidation reaction.

The rational modification of electronic structures to create catalytically active sites has been proved to be a promising strategy to efficiently facilitate the urea oxidation reaction (UOR). Herein, a well-defined nanosheet arrays catalyst of Ni(OH)2 doped with dual cations of Co and Mn on Ni foam (NF) (Co/Mn-Ni(OH)2) is synthesized through a simple hydrothermal process. Benefiting from the advantages of unique structures and modified binding strengths, it is found experimentally that the obtained Co/Mn-Ni(OH)2 catalyst only requires a potential of 1.38 V to deliver a current density of 100 mA cm-2 and exhibits a small Tafel slope of 35 mV dec-1, outperforming single-component-incorporated Ni(OH)2. Moreover, the catalyst has shown excellent stability for 25 h at a current density of 50 mA cm-2. Additionally, first-principles calculations demonstrate that the co-incorporation of Co and Mn remarkably lowers the adsorption barrier of CO(NH2)2* on the catalyst surface, and accelerates the dissociation of the CO(NH2)2* intermediate into CO* and NH* intermediates, which synergistically improve the UOR reaction kinetics. This work provides a generic paradigm for designing advanced and effective catalysts toward the UOR.

A Readily Achieved Potentiostatic Method in Density Functional Theory Calculation for Improved Prediction of the Performance for Electrocatalytic Nitrogen Reduction Reaction.

Accurate prediction of the catalytic performance of nitrogen reduction reaction catalysts based on density functional theory (DFT) calculation is of great significance for developing catalytic materials for nitrogen fixation. However, the applied electrode potential induced the fixation of Fermi level and solvation effect are commonly ignored in the current computational hydrogen electrode method, which leads to the large deviation between the calculation predicted limit potential and the experimentally measured limit potential. In this work, the simple external iteration method is proposed to simulate the Fermi level of the catalysts that are fixed by the applied electrode potential, along with the hybrid solvent model to describe the strong interaction, such as hydrogen bond, between the solvent molecules and the intermediates. This method allowed the theoretical and experimental limit potentials to be in good agreement, indicating the significant effect of the electrode potential and solvation in the DFT calculation. These results will guide the calculation-based prediction of other reaction systems in the field of electrocatalysis.

Laser-induced nitrogen fixation.

For decarbonization of ammonia production in industry, alternative methods by exploiting renewable energy sources have recently been explored. Nonetheless, they still lack yield and efficiency to be industrially relevant. Here, we demonstrate an advanced approach of nitrogen fixation to synthesize ammonia at ambient conditions via laser-induced multiphoton dissociation of lithium oxide. Lithium oxide is dissociated under non-equilibrium multiphoton absorption and high temperatures under focused infrared light, and the generated zero-valent metal spontaneously fixes nitrogen and forms a lithium nitride, which upon subsequent hydrolysis generates ammonia. The highest ammonia yield rate of 30.9 micromoles per second per square centimeter is achieved at 25 °C and 1.0 bar nitrogen. This is two orders of magnitude higher than state-of-the-art ammonia synthesis at ambient conditions. The focused infrared light here is produced by a commercial simple CO2 laser, serving as a demonstration of potentially solar pumped lasers for nitrogen fixation and other high excitation chemistry. We anticipate such laser-involved technology will bring unprecedented opportunities to realize not only local ammonia production but also other new chemistries .

Tuning the Phase Composition of Metal-Organic Framework Membranes for Helium Separation through Incorporation of Fullerenes.

Metal-organic framework (MOF) membranes have attracted significant research interest in gas separation, but efficient helium (He) separation remains a challenge due to the weak polarizability of He and the intrinsic pore size flexibility of MOFs. Herein, incorporated fullerenes (C60 and C70) were used to tune the crystallographic phase composition of ZIF-8 membranes, thus creating small and fixed apertures for selective He permeation. The fullerene-modified ZIF-8 (C60@ZIF-8 and C70@ZIF-8) membranes contain about 20% of the rigid-lattice ZIF-8_I-43m phase and have been prepared as 200-350 nm thick supported layers through electrochemical synthesis. They show a significantly enhanced molecular sieving for He/N2,CH4 together with a satisfactory He permeance of >200 GPU. Specifically, the He/N2 selectivity of the C70@ZIF-8 membrane is up to 30.4, which is much higher than that of the fullerene-free ZIF-8 membrane (5.1) and nearly an order of magnitude higher than those of other reported He-selective MOF membranes. A continuous long-term gas permeation test over 780 h under dry and humid conditions proved the excellent stability of the fullerene-modified ZIF-8 membranes. The general validity and versatility of the proposed strategy for MOF membrane preparation are also demonstrated by the enhancement of the separation performance of a fullerene-modified ZIF-76 membrane.

A Nitrogen Battery Electrode involving Eight-Electron Transfer per Nitrogen for Energy Storage.

Redox flow batteries have been discussed as scalable and simple stationary energy storage devices. However, currently developed systems encounter less competitive energy density and high costs, restricting their wider application. There is a lack of appropriate redox chemistry, preferably based on active materials that are abundant in nature and show high solubility in aqueous electrolytes. A nitrogen-centered redox cycle operating between the limiting species ammonia and nitrate via an eight-electron redox reaction stayed practically unnoticed, albeit its ubiquity in biological processes. Ammonia or nitrate are world-scale chemicals with high aqueous solubility, and are then comparably safe. We demonstrate here the successful implementation of such a nitrogen-based redox cycle between ammonia and nitrate with eight-electron transfer as a catholyte for Zn-based flow batteries, which continuously worked for 12.9 days with 930 charging-discharging cycles. A very competitive energy density of 577 Wh L-1 can be reached, which is well above most reported flow batteries (e.g. 8 times the standard Zn-bromide battery), demonstrating that the nitrogen cycle with eight-electron transfer can offer promising cathodic redox chemistry for safe, affordable, and scalable high-energy-density storage devices.

Fluorine-Stabilized Defective Black Phosphorene as a Lithium-Like Catalyst for Boosting Nitrogen Electroreduction to Ammonia.

Electrocatalytic N2 reduction reaction (NRR) is recognized as a zero-carbon emission method for NH3 synthesis. However, to date, this technology still suffers from low yield and low selectivity associated with the catalyst. Herein, inspired by the activation of N2 by lithium metal, a highly reactive defective black phosphorene (D-BPene ) is proposed as a lithium-like catalyst for boosting electrochemical N2 activation. Correspondingly, we also report a strategy for producing environmentally stable D-BPene by simultaneously constructing defects and fluorination protection based on topochemical reactions. Reliable performance evaluations show that the fluorine-stabilized D-BPene can induce a high NH3 yield rate of ≈70 µg h-1 mgcat. -1 and a high Faradaic efficiency of ≈26 % at -0.5 V vs. RHE in an aqueous electrolyte. This work not only exemplifies the first stable preparation and practical application of D-BPene , but also brings a new design idea for NRR catalysts.

An efficient factor for fast screening of high-performance two-dimensional metal-organic frameworks towards catalyzing the oxygen evolution reaction.

Two-dimensional (2D) metal-organic frameworks (MOFs) are promising materials for catalyzing the oxygen evolution reaction (OER) due to their abundant exposed active sites and high specific surface area. However, how to rapidly screen out highly-active 2D MOFs from numerous candidates is still a great challenge. Herein, based on the high-throughput density functional theory (DFT) calculations for 20 kinds of different transition metal-based MOFs, we propose a factor for fast screening of 2D MOFs for the OER under alkaline conditions (pH = 14.0), that is, when the Gibbs free energy change of the O-O bond formation (defined as ΔG 1) is located at ∼1.15 eV, the peak OER performance would be achieved. Based on the high-throughput calculation results, the prediction factor can be further simplified by replacing the Gibbs free energy with the sum of the associated single point energy (SPE) and a binding energy-dependent term. Guided by this factor, we successfully predicted and then obtained the high-performance Ni-based 2D MOFs. This factor would be a practical approach for fast screening of 2D MOF candidates for the OER, and also provide a meaningful reference for the study of other materials.

Base-free catalytic aerobic oxidation of mercaptans over MOF-derived Co/CN catalyst with controllable composition and structure.

The oxidation of mercaptans under mild and base-free conditions is of vital importance in terms of economy and environment for petroleum processing industry. Here, we developed a series of MOF-derived cobalt-based nitrogen-doped (N-doped) carbon (Co/CN-x) catalysts for the base-free catalytic oxidation of mercaptans. The optimal Co/CN-900 showed excellent catalytic activity for the oxidation of mercaptans under base-free conditions, yielding complete conversion of various mercaptans and > 99.0% selectivity of disulfides. The high performance can be contributed to the advantages of hierarchical pore structure for the diffusion and migration of substrates, self-carrying alkalinity for the formation of mercaptide anion, abundant active Co sites for catalytic oxidation of mercaptans as well as the synergistic effects between the Co nanoparticles (NPs) and N-doped carbon supports. Furthermore, a possible mechanism for base-free catalytic oxidation of mercaptans over Co/CN-x catalysts is proposed based on a set of control experiments and density functional theory (DFT) calculations.

Carbon inserted defect-rich MoS2-X nanosheets@CdSnanospheres for efficient photocatalytic hydrogen evolution under visible light irradiation.

Carbon -MoS2-x@CdS (C-MoS2-x@CdS) core-shell nanostructures with controlled surface sulfur (S) vacancies were prepared via a glucose assisted hydrothermal growth method. The glucose acted as a reducing agent of C-MoS2-X to partially reduce Mo4+ ions to Mo3+ and served as a carbon source to insert the amorphous carbon into the layered MoS2-X simultaneously. The presence of Mo3+ result in the surface S-vacancies, which can provide more additional active sites and enhance the photocatalytic performance. Moreover, the inserted carbon in layered MoS2-X enhanced the electron mobility and decreased the resistance electron transfer. Density functional theory (DFT) calculation confirmed that the surface S-vacancies and the amorphous carbon increase the projected density of states at the conduct band edge, which could enhance the photo-absorption and photo-responsibility. The result is consistent with the photocatalytic H2 production experiment. C2-10%MoS2-x@CdS presented a high H2 evolution rate of 61,494 µmol h-1 g-1 under visible light irrigation (λ ≥ 420 nm), which is 1.98 times and 158 times higher than that of sample without S-vacancies (10%MoS2@CdS) and pure CdS, respectively.

Bidentate carboxylate linked TiO2 with NH2-MIL-101(Fe) photocatalyst: a conjugation effect platform for high photocatalytic activity under visible light irradiation.

Interfacial conjugation was employed to engineering preparation of TiO2@NH2-MIL-101(Fe) heterojunction photocataysts through carboxylate bidentate linkage with TiO2 and NH2-MIL-101(Fe), which can enhance the electron transfer capability from metal-organic frameworks (MOFs) to TiO2 and photocatalytic activity. The carbon nanospheres derived from glucose act as reducing agent and template to synthesize oxygen vacancies TiO2 hollow nanospheres. Then, the oxygen vacancies were employed as antennas to connect 2-aminoterephtalic acid as bidentate carboxylate chelating linkage on TiO2, which have been proved by the density functional theory (DFT) calculations. Subsequently, NH2-MIL-101(Fe) was coordinatingly formed on the surface of TiO2. The conjugation effects between TiO2 and NH2-MIL-101(Fe) enhanced the electron transfer capability and could also induce the band tail states to narrow bandgap of the composites. Thus, the photodegradability of methylene blue was remarkably enhanced under visible light irradiation. The degradation rate of TiO2@17%NH2-MIL-101(Fe) was 0.131 min-1, which was about 3.5 and 65 times higher than that of NH2-MIL-101(Fe) and TiO2, respectively.

Difference between Metal-S and Metal-O Bond Orders: A Descriptor of Oxygen Evolution Activity for Isolated Metal Atom-Doped MoS2 Nanosheets.

Exploration of predictive descriptors for the performance of electrocatalytic oxygen evolution reaction (OER) is significant for material development in many energy conversion processes. In this work, we used high-throughput density functional theory (DFT) calculations to systematically investigate the OER performance of thirty kinds of isolated transition metal atoms-doped ultrathin MoS2 nanosheets (M-UMONs). The results showed that the OER activity could be a function of the decorated transition metal-sulfur (M-S) bond orders with a volcanic-shaped correlation, and a strong correlation could be found when the difference of the M-S bond orders and corresponding metal-oxygen (M-O) bond orders were taken into consideration, implying that the difference in M-S and M-O bond orders could be a predictive descriptor of OER activity for M-UMON system. This successful result also implies this calculation-based method for the exploring of descriptors would also provide a new promising avenue for the discovery of high-performance OER catalysts.