Dual‐metal‐atom‐center catalysts (DACs) are a novel frontier in oxygen electrocatalysis, boasting functional and electronic synergies between contiguous metal centers and higher catalytic activities ...than single‐atom‐center catalysts. However, the definition and catalytic mechanism of DACs configurations remain unclear. Here, a “pre‐constrained metal twins” strategy is proposed to prepare contiguous FeN4 and CoN4 DACs with homogeneous conformations embedded in a N‐doped graphitic carbon (FeCo‐DACs/NC). A programmable phthalocyanines dimer is used as a structural moiety to anchor the bimetallic sites (containing Co and Fe) in a metal–organic framework (MOF) to achieve delocalized dispersion before pyrolysis. The resultant FeCo‐DACs/NC exhibits excellent electrochemical performance in oxygen electrocatalysis and rechargeable Zn–air batteries. Theoretical calculations demonstrate that the synergetic interaction of adjacent metals optimizes the d‐band center position of metal centers and balances the free energy of the *O intermediate, thereby improving the oxygen electrocatalytic activity. This work opens up an avenue for the rational design of DACs with tailored electronic structures and uniform geometric configurations.
A “pre‐constrained metal twin” strategy is presented for the first time to prepare dual‐metal‐atom‐center catalysts (FeCo‐DACs/NC) with continuous FeN4 and CoN4. The FeCo‐DACs/NC delivers excellent catalytic activity in oxygen evolution reaction, oxygen reduction reaction, and Zn–air batteries. The synergistic effect between the two metals optimizes the free energy of the oxygen intermediate state, resulting in improved performance.
Halide perovskites provide an ideal platform for engineering highly promising semiconductor materials for a wide range of applications in optoelectronic devices, such as photovoltaics, light‐emitting ...diodes, photodetectors, and lasers. More recently, increasing research efforts have been directed toward the nonlinear optical properties of halide perovskites because of their unique chemical and electronic properties, which are of crucial importance for advancing their applications in next‐generation photonic devices. Here, the current state of the art in the field of nonlinear optics (NLO) in halide perovskite materials is reviewed. Halide perovskites are categorized into hybrid organic/inorganic and pure inorganic ones, and their second‐, third‐, and higher‐order NLO properties are summarized. The performance of halide perovskite materials in NLO devices such as upconversion lasers and ultrafast laser modulators is analyzed. Several potential perspectives and research directions of these promising materials for nonlinear optics are presented.
Halide perovskites are a promising platform for the construction of nonlinear optical materials in light of their structural diversity, high hyperpolarizability, and bandgap tunability. The current state of the art in purely inorganic and organic–inorganic hybrid halide perovskites as nonlinear optical materials is reviewed and their potential in various nonlinear photonic applications is discussed.
Benefiting from metal–organic frameworks (MOFs) unique structural characteristics, their versatility in composition and structure has been well explored in electrochemical oxygen evolution reaction ...(OER) processes. Here, a ligand/ionic exchange phenomenon of MOFs is reported in alkaline solution due to their poor stability, and the active species and reaction mechanism of MOFs are revealed in the OER process. A series of mixed Ni‐MOFs and Fe‐MOFs are synthesized by straightforward sonication and then directly used as catalyst candidates for OER in alkaline electrolyte. It can be confirmed via ex situ transmission electron microscopic images and X‐ray diffraction patterns analysis, that the bimetallic hydroxide (NiFe‐LDH) is generated in 1.0 m KOH in situ and acts as protagonist for oxygen evolution. The optimized catalyst (FN‐2) exhibits a lower overpotential (275 mV at a current density of 10 mA cm−2) and excellent long‐term stability (strong current density for 100 h without fading). The revelation of the real active species of MOF materials may contribute to better understanding of the reaction mechanism.
A bimetal synergistic electrocatalyst (FN‐2) based on Fe‐MOFs@Ni‐MOFs is successfully synthesized via a simple method. The as‐prepared FN‐2 exhibits superior catalytic activity and stability in the oxygen evolution reaction. A ligand/ionic‐exchange phenomenon of Fe‐MOFs@Ni‐MOFs in alkaline solution is found and it is confirmed that the active species (NiFe‐LDH) is produced in alkali conditions.
•The meaning and significance of the removal of pollutants from wastewater are illustrated.•Representative studies about MOFs for the removal of contaminants from wastewater are ...illustrated.•Perspectives and challenges about the removal of pollutions from wastewater by MOFs are presented.
Water pollution is one of the most serious worldwide problems that endangers the survival and development of human society. Therefore, the effective and efficient removal of contaminants from water has become a hot topic. As a fast-growing branch of coordination chemistry, metal–organic frameworks (MOFs) with tailorable porous structures and numerous active sites have proved to be ideal adsorbents or photocatalysts for water purification. In this review, recent advances in the removal and degradation of water pollutants by MOFs are highlighted. In addition, the challenges and prospects in this active field are also briefly discussed.
The separation and purification of light hydrocarbons (LHs) mixtures is one of the most significantly important but energy demanding processes in the petrochemical industry. As an alternative ...technology to energy intensive traditional separation methods, such as distillation, absorption, extraction, etc., adsorptive separation using selective solid adsorbents could potentially not only lower energy cost but also offer higher efficiency. The need to develop solid materials for the efficiently selective adsorption of LHs molecules, under mild conditions, is therefore of paramount importance and urgency. Metal–organic frameworks (MOFs), emerging as a relatively new class of porous organic–inorganic hybrid materials, have shown promise for addressing this challenging task due to their unparalleled features. Herein, recent advances of using MOFs as separating agents for the separation and purification of LHs, including the purification of CH4, and the separations of alkynes/alkenes, alkanes/alkenes, C5–C6–C7 normal/isoalkanes, and C8 alkylaromatics, are summarized. The relationships among the structural and compositional features of the newly synthesized MOF materials and their separation properties and mechanisms are highlighted. Finally, the existing challenges and possible research directions related to the further exploration of porous MOFs in this very active field are also discussed.
The recent advances of using metal–organic framework (MOF) materials as separating agents in the separation and purification of light hydrocarbons mixtures are summarized. The existing challenges and possible research directions related to the further exploration of porous MOFs in this very active field are also presented.
The seriousness of the energy crisis and the environmental impact of global anthropogenic activities have led to an urgent need to develop efficient and green fuels. Hydrogen, as a promising ...alternative resource that is produced in an environmentally friendly and sustainable manner by a water splitting reaction, has attracted extensive attention in recent years. However, the large‐scale application of water splitting devices is hindered predominantly by the sluggish oxygen evolution reaction (OER) at the anode. Therefore, the design and exploration of high‐performing OER electrocatalysts is a critical objective. Considering their low prices, abundant reserves, and intrinsic activities, NiFe‐based bimetal compounds are widely studied as excellent OER electrocatalysts. Moreover, recent progress on NiFe‐based OER electrocatalysts in alkaline environments is comprehensively and systematically introduced through various catalyst families including NiFe‐layered hydroxides, metal–organic frameworks, NiFe‐based (oxy)hydroxides, NiFe‐based oxides, NiFe alloys, and NiFe‐based nonoxides. This review briefly introduces the advanced NiFe‐based OER materials and their corresponding reaction mechanisms. Finally, the challenges inherent to and possible strategies for producing extraordinary NiFe‐based electrocatalysts are discussed.
This review briefly introduces the advanced NiFe‐based oxygen evolution reaction (OER) materials and their corresponding reaction mechanisms. After providing this background, recent progress on NiFe‐based OER electrocatalysts through various catalyst families is comprehensively and systematically presented, and the inherent challenges and probable strategies for producing extraordinary NiFe‐based electrocatalysts are finally discussed.
Crystalline porous materials have been extensively explored for wide applications in many fields including nonlinear optics (NLO) for frequency doubling, two‐photon absorption/emission, optical ...limiting effect, photoelectric conversion, and biological imaging. The structural diversity and flexibility of the crystalline porous materials such as the metal–organic frameworks, covalent organic frameworks, and polyoxometalates provide numerous opportunities to orderly organize the dipolar chromophores and to systemically modify the type and concentration of these dipolar chromophores in the confined spaces, which are highly desirable for NLO. Here, the recent advances in the crystalline porous NLO materials are discussed. The second‐order NLO of crystalline porous materials have been mainly devoted to the chiral and achiral structures, while the third‐order NLO crystalline porous materials have been categorized into pure organic and hybrid organic/inorganic materials. Some representative properties and applications of these crystalline porous materials in the NLO regime are highlighted. The future perspective of challenges as well as the potential research directions of crystalline porous materials have been also proposed.
In this review, the nonlinear optical properties and applications of crystalline porous materials, including MOFs, COFs, and POMs, are summarized. Such a summary will provide guidelines for the design of crystalline porous materials for nonlinear optics, not only from a basic perspective but also in terms of applications.
Bismuth has emerged as a promising anode material for sodium‐ion batteries (SIBs), owing to its high capacity and suitable operating potential. However, large volume changes during ...alloying/dealloying processes lead to poor cycling performance. Herein, bismuth nanoparticle@carbon (Bi@C) composite is prepared via a facile annealing method using a commercial coordination compound precursor of bismuth citrate. The composite has a uniform structure with Bi nanoparticles embedded within a carbon framework. The nanosized structure ensures a fast kinetics and efficient alleviation of stress/strain caused by the volume change, and the resilient and conductive carbon matrix provides an interconnected electron transportation pathway. The Bi@C composite delivers outstanding sodium‐storage performance with an ultralong cycle life of 30 000 cycles at a high current density of 8 A g−1 and an excellent rate capability of 71% capacity retention at an ultrahigh current rate of 60 A g−1. Even at a high mass loading of 11.5 mg cm−2, a stable reversible capacity of 280 mA h g−1 can be obtained after 200 cycles. More importantly, full SIBs by pairing with a Na3V2(PO4)3 cathode demonstrates superior performance. Combining the facile synthesis and the commercial precursor, the exceptional performance makes the Bi@C composite very promising for practical large‐scale applications.
A Bi nanoparticle@carbon composite is synthesized by a facile heating method from a commercial product of bismuth citrate. Superior sodium storage performance with ultralong cycle life of 30 000 cycles at 8 A g−1 and ultrahigh rate capability of 71% capacity retention at 60 A g−1 are obtained. Full cells by coupling with a well‐developed cathode also deliver impressive capacity and cyclability.
We herein report a rigid nested metal–organic framework (MOF) featuring a unique thermoresponsive gating adsorption behavior, which, in contrast to any known flexibility modes for stimuli‐responsive ...MOFs, depends on the thermal motion of the extra‐framework counterions. In addition, this MOF also exhibits adsorption selectivity of CO2 over N2, H2, and Ar at 273 K, thus enabling a strategic separation and encapsulation of CO2.
A thermal cork screw: Counterions act as removable corks blocking the pore openings of a rigid nested metal–organic framework (MOF). The thermoresponsive gating adsorption behavior of the MOF is dominated by the counterion corks, rather than the flexibility modes of other stimuli‐responsive MOFs. On heating, the corks are removed from the openings, on cooling they return.
Chiral hybrid perovskites have shown great potential for applications in next‐generation optoelectronic devices. The intrinsic asymmetric structures of these chiral hybrid perovskites make them ...particularly promising for second‐order nonlinear optics (NLO). However, it remains still a challenge to obtain ideal perovskite NLO crystals featuring simultaneously large NLO coefficient, good optical transparency, high laser damage threshold, and stable physical and chemical properties, which are highly desirable for practical applications. Herein, a series is constructed of 1D chiral lead halide hybrid perovskites (R/S‐2‐MPD)PbX3 (2‐MPD = 2‐methylpiperidine; X = Cl, Br, I) featuring non‐centrosymmetric architectures. Among them, the (R/S‐2‐MPD)PbBr3 perovskites demonstrate superior performances in second‐order optical nonlinearity, including a large second‐harmonic generation coefficient (≈29.9 pm V–1), wide transparency region (λUV ≈ 310 nm), high laser damage threshold (≈2.84 mJ cm–2), high polarization ratio (up to 96%), and robust physical and chemical stabilities. Such a balanced performance of the chiral lead halide perovskites promises their advanced application in next‐generation photonics devices.
A series of chiral lead halide perovskites (R/S‐2‐MPD)PbX3 have been constructed, of which (R/S‐2‐MPD)PbBr3 exhibits superior second‐order nonlinear opticalproperties. It features a balanced performance with a record second‐order nonlinear optical coefficient, wide transparency region, high laser damage threshold, high polarization ratio, and robust physical and chemical stabilities, which makes it a promising candidate for nonlinear photonics applications.
