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The slighter distortion of the symmetric rac-F crystal restrains the non-radiative decay and engenders intriguing luminescence. However, chiral ligand leads to polar lattice distortion, sparking off the outstanding second-order NLO responses.

A pair of pyridine based fluorenone derivatives with highly efficient second- and third-order nonlinear optical effects have been synthesized.

In principle, porous physisorbents are attractive candidates for the removal of volatile organic compounds such as benzene by virtue of their low energy for the capture and release of this pollutant. Unfortunately, many physisorbents exhibit weak sorbate–sorbent interactions, resulting in poor selectivity and low uptake when volatile organic compounds are present at trace concentrations. Herein, we report that a family of double-walled metal–dipyrazolate frameworks, BUT-53 to BUT-58, exhibit benzene uptakes at 298 K of 2.47–3.28 mmol g−1 at 2BDP = 1,4-di(1H-pyrazol-4-yl)benzene), captures trace levels of benzene, producing an air stream with benzene content below acceptable limits. Furthermore, BUT-55 can be regenerated with mild heating. Insight into the performance of BUT-55 comes from the crystal structure of the benzene-loaded phase (C6H6@BUT-55) and density functional theory calculations, which reveal that C–H···X interactions drive the tight binding of benzene. Our results demonstrate that BUT-55 is a recyclable physisorbent that exhibits high affinity and adsorption capacity towards benzene, making it a candidate for environmental remediation of benzene-contaminated gas mixtures.

Hydrogen, a clean and flexible energy carrier, can be efficiently produced by electrocatalytic water splitting. To accelerate the sluggish hydrogen evolution reaction and oxygen evolution reaction kinetics in the splitting process, highly active electrocatalysts are essential for lowering the energy barriers, thereby improving the efficiency of overall water splitting. Combining the distinctive advantages of metal-organic frameworks (MOFs) with the physicochemical properties of 2D materials such as large surface area, tunable structure, accessible active sites, and enhanced conductivity, 2D MOFs have attracted intensive attention in the field of electrocatalysis. Different strategies, such as improving the conductivities of MOFs, reducing the thicknesses of MOF nanosheets, and integrating MOFs with conductive particles or substrates, are developed to promote the catalytic performances of pristine MOFs. This review summarizes the recent advances of pristine 2D MOF-based electrocatalysts for water electrolysis. In particular, their intrinsic electrocatalytic properties are detailly analyzed to reveal important roles of inherent MOF active centers, or other in situ generated active phases from MOFs responsible for the catalytic reactions. Finally, the challenges and development prospects of pristine 2D MOFs for the future applications in overall water splitting are discussed.

Unlike most gases, acetylene storage is a challenge because of its inherent pressure sensitivity. Herein, a square lattice (sql) coordination network [Cu(4,4′-bipyridine)2(BF4)2]n (sql-1-Cu-BF4) is investigated with respect to its C2H2 sorption behavior from 189 to 298 K. The C2H2 sorption studies revealed that sql-1-Cu-BF4 exhibits multistep isotherms that are temperature-dependent and consistent with the transformation from “closed” (nonporous) to four “open” (porous) phases induced by the C2H2 uptake. The Clausius–Clapeyron equation was used to calculate the performance of sql-1-Cu-BF4 for C2H2 storage at pressures >1 bar, which revealed that its volumetric working capacity at 288 K is slightly superior to acetone (174 vs 170 cm3 cm–3) over a safer pressure range (1–3.5 vs 1–15 bar). Molecular simulations provided insights into the observed switching phenomena, revealing that the layer expansion of sql-1-Cu-BF4 occurs via intercalation and inclusion of C2H2. These results indicate that switching adsorbent layered materials offer promise for utility in the context of C2H2 storage and delivery.

Carboxylic acid-based metal-organic frameworks (MOFs) are normally passed for the “pre-catalysts” for oxygen evolution reaction (OER) due to the hydroxides constructed in-situ during its alkaline hydrolysis process (AHP) in lye. Whereas, it remains a mystery that they show advantageous activity over prototypical hydroxides when they are directly acted as OER catalysts. Herein, we propose for the first time that the steric hindrance effect of Nafion can induce enhanced catalytic activity of such MOFs. Different from conventional catalysts without AHP, the Nafion with 3D structure weakens the AHP of Co-MOF nanoribbons, thus forming small size and low crystallinity species (cobalt hydroxide) with more active sites. And the existence of Nafion also optimizes its electronic structure, which is confirmed by transmission electron microscopy (TEM), in-situ UV absorption spectra, in-situ Raman spectroscopy and so on. Compared with Co-MOF-K obtained by directly immersing the Co-MOF nanoribbons in 1.0 M KOH, the Co-MOF-NK obtained by AHP of Co-MOF mixed with Nafion shows better catalytic activity. Based on the above inspiration, we realized the low overpotential of 268 mV at 10 mA·cm−2 by preparing CoFe-MOF-NK. This work provides a new understanding of the structural reconstruction of MOFs in the field of electrocatalysis.

High sensitivity and selectivity for the detection of metal ions are very important to protect human health. Fluorescent metal–organic frameworks (MOFs) as new sensing materials have attracted more and more attention. Herein, a pillar-layered fluorescent metal–organic framework, {[H2N(CH3)2]2[Cd5(TCPE)3(4,4′-bpy)2(MeOH)2(H2O)4]}n (NKM-102) (H4TCPE = tetrakis(4-carboxyphenyl)ethylene acids, 4,4′-bpy = 4,4′-bipyridine), has been synthesized through utilization of the H4TCPE ligand with typical AIE characteristics. NKM-102 exhibits excellent fluorescence emission performance and detects Al3+ ions with high selectivity through turn-off effect and emission color change. Moreover, the detection limit of NKM-102 can reach 158 ppb, which is lower than the maximum limit of Al3+ ions in drinking water recommended by the United States Environmental Protection Agency (200 ppb). Therefore, the NKM-102 probe is a prominent candidate for the visual detection of Al3+ ions with high sensitivity and selectivity.

Cobalt disulfide (CoS2) has been considered a promising anode material for lithium-ion batteries (LIBs) due to its high theoretical capacity of 870 mA h g−1. However, its practical applications have been hampered by undesirable cycle life and rate performance due to the volume change and deterioration of electronic conductivity during the discharge-charge process. In this study, an interconnected CoS2/N-doped carbon/carbon nanotube (CoS2/NC-CNTs-700) network was successfully prepared to boost its lithium storage performance, in which small-size CoS2 nanoparticles were confined by N-doped carbon and uniformly decorated on the surface of CNTs. N-doped carbon can effectively accommodate the large volume expansion of CoS2 nanoparticles. Additionally, the 3D conductive nanostructure design offers adequate electrical/mass transport spacing. Benefiting from this, the CoS2/NC-CNTs-700 electrode demonstrates a long cycle life (a residual capacity of 719 mA h g−1 after 100 cycles at 0.2 A g−1) and outstanding rate performance (335 mA h g−1 at 5.0 A g−1). This study broadens the design and application of CoS2 and fosters the advances in battery anode research.

Two nanosize lanthanide clusters Na3[Eu48O6(OH)84(tca)34(gly)12(H2O)22]2Htca6Cl6H2ONO3 (Eu48) and Na[Tb48O6(OH)84(fca)26(dmp)14(H2O)24]4HfcaNO38Cl (Tb48) have been isolated in presence of th...

Introducing the chiral spacers to two-dimensional (2D) lead halide perovskites (LHPs) enables them to exhibit circularly polarized photoluminescence (CPPL), which could have applications in chiral-optics and spintronics. Despite that a great deal of effort has been made in this field, the reported polarization degree of CPPL at ambient conditions is still very limited, and the integration of multiple functionalities also remains to be explored. Here we report the structures, CPPL, and piezoelectric energy harvesting properties of chiral 2D LHPs, [

Two metal–organic frameworks, {(NH2Me2)[Zn(Pycia)]}n (MOF-1) and {(NH2Me2)[Zn2(Pycia)(PBA)]}n (MOF-2), have been synthesized based on pyrazole functionalized carboxylic acid ligands for organic dye adsorption. The enlarged pore dimension of MOF-2 suggests the advantage of additional linear auxiliary ligand for the structure tuning of the MOFs. Furthermore, the anionic frameworks of the MOFs endow them with size selective adsorption toward different cationic organic dyes.

Metal-organic frameworks (MOFs), comprised of metal ions/clusters and organic ligands, have shown promising potential for numerous applications. Recently, luminescent MOFs (LMOFs), with the superiorities of inherent crystallinity, definite structure, tunable pore, and multiple functionalizations, have bloomed out as sensors for the detection. Numerous LMOFs have been synthesized and used for sensing applications. Herein, the recent advances of LMOFs as chemical sensors for the detection of diverse targets, including metal ions, anions, small molecules, volatile organic compounds, nitro-aromatic explosives, gases, and biomolecules, have been summarized. Additionally, the detection mechanisms and the relationship between structure and properties of the materials are also illustrated. This review could be useful reference for the rational construction and sensing applications of LMOFs.

Nickel sulfides are suitable anode materials for sodium-ion batteries (SIBs) because of their moderate cost and high theoretical capacity. Nevertheless, low cycling stability and rate performance caused by volume expansion and inferior electronic conductivity during the charge/discharge process still hamper their development. Herein, Ni3S2 nanoparticles uniformly embedded in N-doped carbon nanosheets (Ni3S2@C) are synthesized by sulfuration of a Ni-based metal-organic framework (Ni-MOF), followed by coating with polypyrrole (PPy). The PPy protects Ni3S2 particles from aggregation, and is converted to N-doped carbon shell during the annealing process. The nano-sized structure accelerates reaction kinetics and minimizes stress/strain caused by volume changes. The N-doped carbon nanosheets connect the transmission pathway of the electrons, and buffer the volume change during the electrochemical reaction. As expected, NiSx@C-600 delivers superior sodium storage performance with a high discharge capacity of 432.8 mA h g−1 at 0.2 A g−1 over 100 cycles and remarkable rate capacity of 371.6 mA h g−1 at a high rate of 6.4 A g−1. To the best of our knowledge, the obtained nanosheets exhibit the best rate performance among current Ni3S2 composites. The proposed method for enhancing conductivity and doping heteroatom by using PPy provides a novel insight to design SIB anodes with superior performance.

International audience; The structural reconstruction at the crystal layer edges of 2D lead halide perovskites (LHPs) leads to unique edge states (ES) which are manifested by prolonged carrier lifetime and reduced emission energy. These special ES could effectively enhance the optoelectronic performance of devices, but their intrinsic origin and working mechanism remain elusive. Here we demonstrate that the ES of a family of 2D Ruddlesden-Popper LHPs [BA2CsPb2Br7, BA2MAPb2Br7 and BA2MA2Pb3Br10 (BA = butylammonium; MA = methylammonium)] arise from the rotational symmetry elevation of the PbBr6 octahedra dangling at the crystal layer edges. These dangling octahedra give rise to localized electronic states that enable an effective transport of electrons from the interior to layer edges, and the population of electrons in both the intrinsic states and ES can be manipulated via controlling the external fields. Moreover, the abundant phonons, activated by the dangling octahedra, can interact with electrons to facilitate radiative recombination, counterintuitive to the suppressive role commonly observed in conventional semiconductors. This work unveils the intrinsic atomistic and electronic origins of ES in 2D LHPs, which could stimulate the exploration of ES-based exotic optoelectronic properties and corresponding design of high-performance devices for these emergent low-dimensional semiconductors.

Managing elastic properties of ABX3 type molecular perovskite ferroelectrics is critical to their future applications since these parameters determine their service durability and reliability in devices. The abundant structural and chemical viability of these compounds offer a convenient way to manipulate their elastic properties through a facile chemical approach. Here, the elastic properties and high-pressure behaviors of two isostructural perovskite ferroelectrics, MDABCO-NH4 I3 and MDABCO-KI3 (MDABCO = N-methyl-N'-diazabicyclo[2.2.2]octonium) is systematically investigated, via the first principles calculations and high-pressure synchrotron X-ray diffraction experiments. It is show that the simple replacement of NH4 + by K+ on the B-site respectively results in up to 48.1%, 52.4%, and 56.3% higher Young's moduli, shear moduli and bulk moduli, which is attributed to the much stronger KI coordination bonding than NH4 …I hydrogen bonding. These findings demonstrate that it is possible to tune elastic properties of molecular perovskite ferroelectrics via simply varying the framework assembling interactions.

Owing to their rich porosity and structural diversity, metal-organic frameworks (MOFs) offer substantial advantages over other emission sources for the precise design and color regulation of white-light phosphors. However, achieving efficient white-light emission remains a considerable challenge. Herein, we report a strategy to achieve tunable and efficient white-light emission by regulating energy transfer in a multicomponent dye-loaded MOF. An anionic MOF

Efficient charge separation and utilization are critical factors in photocatalysis. Herein, it is demonstrated that the complete spatial separation of oxidation and reduction cocatalysts enhances the efficacy of charge separation and surface reaction. Specifically, a Pt@NH2 -UiO-66@MnOx (PUM) heterostructured photocatalyst with Pt and MnOx as cocatalysts is designed for the optimization of the NH2 -UiO-66 photocatalyst. Compared with the pristine NH2 -UiO-66, Pt@NH2 -UiO-66 (PU), and NH2 -UiO-66@MnOx (UM) samples, the PUM sample exhibits the highest hydrogen production activity. As cocatalysts, Pt favors trapping of electrons, while MnOx tends to collect holes. Upon generation from NH2 -UiO-66, electrons and holes flow inward and outward of the metal-organic framework photocatalyst, accumulating on the corresponding cocatalysts, and then take part in the redox reactions. The PUM photocatalyst greatly prolongs the lifetime of the photogenerated electrons and holes, which favors the electron-hole separation. Furthermore, the PUM sample facilitates overall water splitting in the absence of sacrificial agents, thereby demonstrating its potential as a modification method of MOF-type semiconductors for the overall water-splitting reaction.

Hybrid organic-inorganic perovskites have emerged as promising thermoelectric materials due to their attractive figure of merits. To further reduce their thermal conductances (G) and improve the thermoelectric efficiencies, fabrication of phononic crystals (PnCs) could be an effective approach. In this work, CH3NH3PbI3-based PnCs were developed and their thermal transports were engineered by optimizing the configurations of both basal bodies and scatterers. Our cross-scale simulations demonstrate that low relative G can be achieved in CH3NH3PbI3 PnCs with large scatterers but low-symmetric PnC lattices, basal bodies, and scatterers. Moreover, we discovered the increased disorder of CH3NH3+ cations from tetragonal to cubic transition significantly increases the phonon velocities and reverses the phonon transport from diffusive to quasi-ballistic, leading to an abnormal reduction of relative G. This work provides a new pathway for engineering thermal conductivity of hybrid perovskites and improving the performance of corresponding devices.

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.

Aimed at the exploration of luminescent coordination polymer (LCP) systems for highly tunable luminophores, a new series of Cd(II) LCPs, namely, [Cd2(tpt)2(CBA)2(H2O)2]·(PAH) (1), [Cd2(tpt)2(CBA)2]·(PAHs) (2–3) (tpt = 2,4,6-tri(pyridin-4-yl)-1,3,5-triazine, H2CBA = 4-(carboxymethyl) benzoic acid, PAHs = polycyclic aromatic hydrocarbons, coronene for 1, perylene for 2, and triphenylene for 3), are successfully constructed based on the host–guest charge transfer (HGCT) mechanism. Through the PAHs directed coordination assembly of Cd(II) ions, CBA2– and tpt ligands, compounds 1–3 exhibit the as-expected host–guest structures, in which PAHs-tpt donor–acceptor (D–A) systems are successfully achieved. Structural investigations of 1–3 show that the flexibility of the carboxylate ligand and the guest dependent donor–acceptor interaction affect their structures. In addition, 1–3 exhibit a guest-dependent wide emission range originating from the charge-transfer interactions of the D–A systems. What is more, the ove...

Metal–organic frameworks (MOFs) have been utilized as templates/precursors for the synthesis of metal oxide anode materials of lithium-ion batteries, due to their large accessible surface, tunable pore size, and various metal centers. However, the same phase of materials derived from different MOFs could show diverse capacities and performances. In this study, aiming at an in-depth understanding of the structural relationship between the precursors and the product, we chose two MOFs with the same linker as templates/precursors for Co3O4 nanomaterials. The structure and component evolution in the pyrolysis process were analyzed, and the electrochemical properties of the resulting Co3O4 were studied. The results showed that the concentration of metal centers and the strength of coordination bonds in the MOFs were critical factors that determined the morphology and performances of the resulting material.

The electronic structures and elastic properties of three isostructural, metal-free perovskite materials, (C4N2H12)(NH4X3)·H2O (PIP-X, X = Br, Cl, I), were examined using density functional theory (DFT) calculations and high-pressure synchrotron X-ray diffraction experiments. The calculated band structures and density of states demonstrate that all the compounds possess large direct bandgaps of 5.34 eV for PIP-Cl, 4.67 eV for PIP-Br, and 4.13 eV for PIP-I. With the bromide and iodide, the valence band maximum and conduction band minimum mainly arise from the 3p- and 3s-states of the halogens, whereas the conduction band minimum of the chloride is dominated by the s-states of the nitrogen from the ammonium. Such an inverse dependence of bandgaps on the halogen radius originates from the increased band dispersions because of reduced halogen electronegativity. In addition, the full elastic constants of these compounds were calculated using DFT which enables the systematic mapping of their Young's moduli, shear moduli and Poisson's ratios. The N–H⋯X bond strength governed by the halogen radius is primarily responsible for the discrete modulus properties in these compounds. Notably, these metal-free perovskites constructed using hydrogen bonds exhibit comparable rigidity with their hybrid organic–inorganic counterparts assembled using coordination bonds. Furthermore, the high-pressure synchrotron powder X-ray diffraction experiments were performed on PIP-Br, which not only validated the DFT results but also revealed its comparable stiffness to methylammonium lead bromine (CH3NH3PbBr3) under hydrostatic stress.

Two new metal-drug complexes constructed from non-toxic zinc and theophylline (TPL), an anti-asthmatic active drug, have been introduced into a release system based on matrices of hydroxypropylmethylcellulose (HPMC) and microcrystalline cellulose (MC). The release rate of TPL from the metal-drug complexes could be controlled by the amount of MC added, and the release mechanism changed from anomalous transport to Fickian diffusion.

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 was proposed to prepare contiguous FeN4 and CoN4 DACs with homogeneous conformations embedded in an N-doped graphitic carbon (FeCo-DACs/NC). A programmable phthalocyanines dimer was 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 exhibited excellent electrochemical performance in oxygen electrocatalysis and rechargeable Zn-air batteries. Theoretical calculations demonstrated that the synergetic interaction of adjacent metals optimized the d-band center position of metal centers and balanced 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. This article is protected by copyright. All rights reserved.

Hybrid organic-inorganic piezoelectrics have attracted attention due to their simple synthesis, mechanical flexibility, and designability, which have promising application potential in flexible sensing and self-powered energy harvesting devices. Although some hybrid piezoelectrics are discovered, most of their structures are limited by the perovskite-type and often contain lead. Herein, the synthesis, structure, and piezoelectric properties of a new hybrid lead-free metal halide, (BTMA)2 CoBr4 (BTMA = benzyltrimethylammonium) are reported. The experimental and theoretical results demonstrate that this material simply composed of [CoBr4 ]2- tetrahedra and BTMA+ cations exhibits significant piezoelectricity (d22 = 5.14, d25 = 12.40 pC N-1 ), low Young's and shear moduli (4.11-17.56 GPa; 1.86-7.91 GPa). Moreover, the (BTMA)2 CoBr4 /PDMS (PDMS = polydimethylsiloxane) composite thin films are fabricated and optimized. The 10% (BTMA)2 CoBr4 /PDMS-based flexible devices show attractive performance in energy harvesting with an open-circuit voltage of 19.70 V, short-circuit current of 4.24 µA, and powder density of 11.72 µW cm-2 , catching up with those of piezoelectric ceramic composites. Meanwhile, these film devices show excellent capability in accurately sensing human body motions, such as finger bending and tapping. This work demonstrates that (BTMA)2 CoBr4 and related piezoelectric lead-free halides can be promising molecular materials in modern energy and sensing applications.

The supermolecular recognition properties of a 2D coordination polymer, namely, [Cd2(3-tpt)(bpta)(H2O)3] (1) (3-tpt = 2,4,6-tris(3-pyridyl)-1,3,5-triazine and H4bpta = 1,1′-biphenyl-2,2′,6,6′-tetracarboxylic acid), are reported herein. Complex 1 shows a porous supermolecular framework with strong inter-layer π–π interaction from the triazine moieties of 3-tpt ligands. By utilizing its porous nature and triazine induced π–π interaction, complex 1 reveals specific supramolecular recognition and structure transformation toward benzene homologues, which is proved straightforwardly by structure investigations. Furthermore, the altered inter-layer π–π interaction of 1 in response to the molecule recognition also affects its emission properties, which indicates its potential in sensing applications.

Metal-organic frameworks (MOFs) with high hydrolytic stability are highly needed to prepare polymer-MOFs hybrid membranes working in aqueous solution media. In this study, [Eu(BTB)(H2O)2·solvent]n (abbreviated as EuBTB), a kind of lanthanide-based two-dimensional MOFs, was utilized to prepare hybrid membranes for organic solvent dehydration owing to their hydrolytic stability arising from the relatively strong coordination bond between lanthanide ions and oxygen-containing groups. The detailed structure and properties of the hybrid membranes were well characterized. The hybrid membranes exhibited high mechanical strength and swelling resistance due to the strong interfacial interaction benefiting from the well complexation of EuBTB and sodium alginate (SA) through carboxylic groups. The horizontally aligned lamellar EuBTB could render ordered channels with the diameter of 0.5–0.8 nm. Each Eu3+ in EuBTB could coordinate two water molecules and serves as carriers to facilitate the transportation of water molecules. Moreover, the incorporated EuBTB could render decreased crystallinity. Accordingly, the hybrid membranes exhibited superior permeability and selectivity for ethanol dehydration. Especially, the membrane containing 5 wt% EuBTB exhibited an optimum performance with permeation flux of 1996 g/m2 h and separation factor of 1160 for 90 wt% ethanol aqueous solution at 350 K. Meanwhile, the hybrid membranes showed good long-term stability. This study may offer a generic and efficient approach to prepare MOFs-based hybrid membranes with high performance and stability for water-selective separation.

Dynamic metal-organic frameworks (MOFs) that respond to external stimuli have recently attracted great attention. However, the subtle control of dynamic processes as well as the illustration of the underlying mechanism, which is crucial for the targeted construction and modulation purpose, is extremely challenging. Herein, we report the achievement of simultaneous kinetic and thermodynamic modulation of the structure transformation processes of a family of cobalt(II)-organic frameworks, through the rational combination of coligand replacement, solvent molecule substitution, and ligand-based solid solution strategies. On the basis of the systematic investigation of the structural transformation behaviors, the underlying response mechanism and principles for modulation were illustrated. It is expected that this work can provide valuable hints for the study and further development of dynamic materials.

Nowadays, the hybrids of non-noble metal and heteroatom-doped carbon, especially, transition-metal-nitrogen-carbon materials, have been extensively studied as promising next-generation oxygen reduction reaction (ORR) catalysts in energy conversion. However, the pyrolysis of normal metal/nitrogen/carbon-containing precursors usually generates uncontrollable agglomeration or inhomogeneous microstructure, hence leading to insufficient exposure of the active sites and poor mass transport. In this work, a new strategy for fabricating N-doped-carbon-coated Fe3O4 (denoted as NC@Fe3O4) is proposed by the pyrolysis of polyaniline (PANI)-coated Fe-based metal organic frameworks (MIL-101-Fe). The optimal catalyst exhibits a very positive ORR onset potential close to that of Pt/C, quasi-four-electron-transfer pathway and high long-term cycle stability in alkaline media. This work demonstrates the crucial role of thin PANI film (a highly conductive skeleton and heteroatoms sources) together with MOFs to rationalize the superior ORR performance for the resulting NC@Fe3O4. The generality of the conductive-polymer-layer-assisted synthetic strategy is expected to further boost the electrocatalytic activity of universal non-noble-metal hybrid electrocatalyst for practical fuel-cell applications.

As a kind of MOFs, cage-based MOFs usually carry large voids and small windows, which are advantageous to the storage of small molecules that remain kinetically trapped inside the cages (confinement effect). By adjusting the size of windows via reticular synthesis, the cage-based MOFs can selectively capture and separate the suitable size molecules. Here, considering angle-directed and face-directed strategies, a novel multicage-based MOF NUM-3 with a new (3,4,5)-connected topology was successfully constructed in the mixed-ligands assembly. In the framework of NUM-3, there exist four different kinds of cages, which exhibit diverse polyhedral configurations. The four kinds of cages in the order ABCDDCBA as the minimum repeat unit form a 1D tortuous channel along the c axis. Based on the structure characteristics that the 1D channel exhibits different inner diameter (from 4.0 to13.0 A), NUM-3a (actived NUM-3) can capture CO2 over C2H4 and C2H6 by the size selectivity (the empirical kinetic diameters: CO2 < ...

In order to elucidate the effect of the structure on stability and gas adsorption performance, three porous Zn(II) metal–organic frameworks, NKU-106, NKU-107, and NKU-108, have been constructed. NKU-106 and NKU-107 assembled from acylamide functionalized tetracarboxylate ligand exhibit low stability and thereby poor gas adsorption ability. However, when one isophthalate moiety of the tetracarboxylate ligand is replaced with a pyrazole group, and the resulting NKU-108 shows improved thermal and chemical stability as well as good adsorption capacities with respect to CO2 and C2 hydrocarbons. This result demonstrates that coordination group optimization is an effective strategy to improve the stability and gas adsorption properties of metal–organic frameworks (MOFs) and thus provides very valuable information for future design and synthesis of porous MOFs for practical application.

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.

Controlled growth of metal-organic frameworks (MOFs) nanocrystals on requisite surfaces is highly desired for myriad applications related to catalysis, energy, and electronics. Here, this challenge is addressed by overlaying arbitrary surfaces with a thermally evaporated metal layer to enable the well-aligned growth of ultralong quasi-2D MOF nanoarrays comprising cobalt ions and thiophenedicarboxylate acids. This interfacial engineering approach allows preferred chelation of carboxyl groups in the ligands with the metal interlayers, thereby making possible the fabrication and patterning of MOF nanoarrays on substrates of any materials or morphologies. The MOF nanoarrays grown on porous metal scaffolds demonstrate high electrocatalytic capability for water oxidation, exhibiting a small overpotential of 270 mV at 10 mA cm-2 , or 317 mV at 50 mA cm-2 as well as negligible decay of performance within 30 h. The enhanced performance stems from the improved electron and ion transport in the hierarchical porous nanoarrays consisting of in situ formed oxyhydroxide nanosheets in the electrochemical processes. This approach for mediating the growth of MOF nanoarrays can serve as a promising platform for diverse applications.

The synergy of a stretchy ligand and highly variable π-π interaction has been proposed as a rational strategy for the construction of breathing metal-organic frameworks (MOFs). Based on this strategy, a breathing MOF, {[Cd

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.

Aiming at the targeted construction of coordination polymer luminophores, the engineering of host–guest architectures with charge transfer based emissions is performed by utilizing the interactions between the electron-deficient 2,4,6-tri(pyridin-4-yl)-1,3,5-triazine (tpt) and electron-rich polycyclic aromatic hydrocarbons (PAHs) motifs as acceptors and donors, respectively. Through guest modulation of a prototype coordination polymer [Cd(tpt)(1,4-pda)(H2O)2]·(tpt)·(H2O)2 (1) (1,4-H2pda = 1,4-phenylenediacetic acid), a series of coordination polymers with different PAHs as guests, [Cd2(tpt)2(1,4-pda)2]·guest (2–5) (guest = triphenylene for 2, pyrene for 3, coronene for 4, and perylene for 5), are successfully fabricated. Distinct from 1, coordination polymers 2–5 reveal unique bilayer structures with PAHs interlayer and good stability, owing to the enhanced stacking interactions between tpt motifs and PAH guests. Moreover, their emissions cover a wide range of wavelength due to the effective guest to host...

Isostructural CoII and MnII organic frameworks with anionic frameworks and counterions (Me2NH2)+, namely {[M2Cl2(BTC)4/3]·(Me2NH2)+2·4/3H2O}n (M = Co (1) and Mn (2)), have been constructed by one-pot synthesis. Complexes 1 and 2 take paddle-wheel-like dinuclear metal cluster-based three-dimensional structures. Thermogravimetric analysis and variable-temperature powder X-ray diffraction spectra suggested that 1 displays better thermal stability than 2. Both exhibit relatively high proton conductivities at 65% relative humidity (RH) and room temperature (σ > 2.5 × 10–4 S cm–1); however, complex 1 possesses the better cycling capability and stability with Ea = 0.21 eV under 65% RH.

In this paper, two 3D anionic metal–organic frameworks, [(CH3CH2)2NH2]·[Zn(BTC)1/3(PyC)]·1/2CH3CN·2H2O (NKU-102) and [(CH3CH2)2NH2]·[Zn2(BTC) (PyC)]·1.5H2O·DEF (NKU-103), were constructed from the same reaction system at different temperature. Though both are of anionic framework, NKU-102 possesses a sealed 3D framework based on octahedral cage and shows negligible adsorption capacity of organic dyes, whereas NKU-103 features an open triangular microchannel surrounded by two types of helical chains, and thus exhibits outstanding size-selective adsorption toward small cationic organic dyes.

Manganese oxides (MnOx ) are promising anode materials for lithium ion batteries, but they generally exhibit mediocre performances due to intrinsic low ionic conductivity, high polarization, and poor stability. Herein, yolk-shell nanorods comprising of nitrogen-doped carbon (N-C) coating on manganese monoxide (MnO) coupled with zinc manganate (ZnMn2 O4 ) nanoparticles are manufactured via one-step carbonization of α-MnO2 /ZIF-8 precursors. When evaluated as anodes for lithium ion batteries, MnO@ZnMn2 O4 /N-C exhibits an reversible capacity of 803 mAh g-1 at 50 mA g-1 after 100 cycles, excellent cyclability with a capacity of 595 mAh g-1 at 1000 mAg-1 after 200 cycles, as well as better rate capability compared with those non-N-C shelled manganese oxides (MnOx ). The outstanding electrochemical performance is attributed to the unique yolk-shell nanorod structure, the coating effect of N-C and nanoscale size.

In this work, an L-shaped silver complex, AgLClO4 (L = 2,3-bis[3-(pyridin-2-yl)-1H-pyrazol-1-yl·methyl]quinoxaline), M, is found to be adaptable enough to host a range of medium and large aromatic hydrocarbons including several polycyclic aromatic hydrocarbons (PAHs). The transformation of M from as-synthesized closed (nonporous) crystalline to at least three types of open phase structures in the presence of different aromatic hydrocarbons enables the adaptable binding of M to these aromatics. In essence, M can rearrange its cavities to fit the different sizes and shapes of the guest molecules in the manner that is infeasible with cage compounds or coordination networks. Single-crystal and powder X-ray diffraction confirm the adaptable structures of the resulting host-guest complexes, M·nG (G = guest, n = 0.5 or 0.75). Detailed 1D and 2D nuclear magnetic resonance spectra, along with the fluorescence spectroscopy, reveal that the host-guest complexes feature similar chemical compositions in the solution, but are in the states of rapid exchange in and outside the cages. Such an adaptability of M provides insights into the strength of host-guest interactions and enables a new class of adsorptive molecular materials that can bind a large number of aromatics, specifically PAHs.