High-Valence Metal Doping Induced Lattice Expansion for M-FeNi LDH toward Enhanced Urea Oxidation Electrocatalytic Activities.

The precise design of low-cost, efficient, and definite electrocatalysts is the key to sustainable renewable energy. The urea oxidation reaction (UOR) offers a promising alternative to the oxygen evolution reaction for energy-saving hydrogen generation. In this study, by tuning the lattice expansion, a series of M-FeNi layered double hydroxides (M-FeNi LDHs, M: Mo, Mn, V) with excellent UOR performance are synthesized. The hydrolytic transformation of Fe-MIL-88A is assisted by urea, Ni2+ and high-valence metals, to form a hollow M-FeNi LDH. Owing to the large atomic radius of the high-valence metal, lattice expansion is induced, and the electronic structure of the FeNi-LDH is regulated. Doping with high-valence metal is more favorable for the formation of the high-valence active species, NiOOH, for the UOR. Moreover, the hollow spindle structure promoted mass transport. Thus, the optimal Mo-FeNi LDH showed outstanding UOR electrocatalytic activity, with 1.32 V at 10 mA cm-2 . Remarkably, the Pt/C||Mo-FeNi LDH catalyst required a cell voltage of 1.38 V at 10 mA·cm-2 in urea-assisted water electrolysis. This study suggests a new direction for constructing nanostructures and modulating electronic structures, which is expected to ultimately lead to the development of a class of auxiliary electrocatalysts.

Monodispersed Pt Sites Supported on NiFe-LDH from Synchronous Anchoring and Reduction for High Efficiency Overall Water Splitting.

Precise design of low-cost, efficient and definite electrocatalysts is the key to sustainable renewable energy. Herein, this work develops a targeted-anchored and subsequent spontaneous-redox strategy to synthesize nickel-iron layered double hydroxide (LDH) nanosheets anchored with monodispersed platinum (Pt) sites (Pt@LDH). Intermediate metal-organic frameworks (MOF)/LDH heterostructure not only provides numerous confine points to guarantee the stability of Pt sites, but also excites the spontaneous reduction for PtII . Electronic structure, charge transfer ability and reaction kinetics of Pt@LDH can be effectively facilitated by the monodispersed Pt moieties. As a result, the optimized Pt@LDH that with the 5% ultra-low content Pt exhibits the significant increment in electrochemical water splitting performance in alkaline media, which only afford low overpotentials of 58 mV at 10 mA cm-2 for hydrogen evolution reaction (HER) and 239 mV at 10 mA cm-2 for oxygen evolution reaction (OER), respectively. In a real device, Pt@LDH can drive an overall water-splitting at low cell voltage of 1.49 V at 10 mA cm-2 , which can be superior to most reported similar LDH-based catalysts. Moreover, the versatility of the method is extended to other MOF precursors and noble metals for the design of ultrathin LDH supported monodispersed noble metal electrocatalysts promoting research interest in material design.

Rational regulation of acetylene adsorption and separation for ultra-microporous copper-1,2,4-triazolate frameworks by halogen hydrogen bonds.

It is well known that the introduction of exposed fluorine (F) sites into metal-organic frameworks (MOFs) can effectively promote acetylene (C2H2) adsorption via C-H⋯F hydrogen bonds. However, such super strong hydrogen bonding interactions usually lead to very high acetylene adsorption enthalpy and thus require more energy during the adsorbent regeneration process. As the same group elements, chlorine (Cl), bromine (Br) and iodine (I) also can act as hydrogen bond acceptors but with relatively weak forces. So, it is speculated that the decoration of Cl, Br or I sites on the pore surface of MOF adsorbents may enhance acetylene adsorption but with lower energy consumption. Herein, ultra-microporous MOFs constructed by Cu4X4 (X = Cl, Br, I) motifs and 1,2,4-triazolate linkers, namely, [Cu8X4(TRZ)4]n (TRZ = 3,5-diethyl-1,2,4-triazole or detrz for SNNU-313-X, and 3,5-dipropyl-1,2,4-triazole or dptrz for SNNU-314-X), provide an ideal platform to investigate the effect of C-H⋯X (X = Cl, Br, I) hydrogen bonding on C2H2 adsorption and purification performance. Benefiting from the small pore size and pore environment, the C2H2 uptake and separation properties of this series of MOFs are systematically regulated. Detailed gas adsorption results show that with the same organic linker, the C2H2 uptake and separation (C2H2/C2H4 and C2H2/CO2) performance decrease clearly with the electronegativity of halogen ions (SNNU-313-Cl > SNNU-313-Br > SNNU-313-I). With the same halogen ion, the gas adsorption decreases with the bulk of decorated alkyl groups (SNNU-313-Cl > SNNU-314-Cl). Remarkably, SNNU-313/314 series MOF adsorbents exhibit moderate C2H2 uptake capacity and high separation ability, but the C2H2 adsorption enthalpies are much lower than those of MOF materials with exposed F sites. Dynamic fixed-bed column breakthrough experiments and Grand Canonical Monte Carlo (GCMC) simulations further indicate the critical effects of halogen hydrogen bonds on acetylene adsorption and separation. Overall, this work demonstrated an effective regulation of acetylene adsorption and separation by rational C-H⋯X hydrogen bonding, which may provide a new route for the exploration of energy-efficient acetylene adsorbent materials.

Micropore Regulation in Ultrastable [Sc3O]-Organic Frameworks for Acetylene Storage and Purification.

High storage capacity, high separation selectivity, and high structure stability are essential for an idea gas adsorbent. However, it is not easy to achieve all three at the same time, even for the promising metal-organic framework (MOF) adsorbents. We demonstrate herein that robust [Sc3O]-organic frameworks could be regulated by a micropore combination strategy for high-performance acetylene adsorption. Under the same solvent system with formic acid as a modulator, similar tritopic ligands extend [Sc3O(COO)6] trigonal-prismatic clusters to generate SNNU-5-Sc and SNNU-150-Sc adsorbents. Notably, the two Sc-MOFs can keep their architectures over 24 h in water at different pH values (2-12) or at 90 °C. Modulated by the linker symmetry, the final stacking metal-organic polyhedral cages produce open window sizes of about 10 Å for SNNU-5-Sc and 5 Å + 7 Å for SNNU-150-Sc. Due to such micropore combinations, SNNU-5-Sc exhibits a top-level C2H2 uptake of 211.2 cm3 g-1 (1 atm and 273 K) and SNNU-150-Sc shows high C2H2/CH4, C2H2/C2H4, and C2H2/CO2 selectivities of 80.65, 4.03, and 8.19, respectively, under ambient conditions. Dynamic breakthrough curves obtained on a fixed-bed column and grand canonical Monte Carlo (GCMC) simulations further support their prominent acetylene storage and purification performance. High framework stability, storage capacity, and separation selectivity make SNNU-5-Sc and SNNU-150-Sc ideal acetylene adsorbents in practical applications.

Cobalt phosphide nanorings towards efficient electrocatalytic nitrate reduction to ammonia.

High-quality CoP nanorings (CoP NRs) are easily achieved using a phosphorating treatment of CoOOH nanorings, and reveal high activity towards the hydrogen evolution reaction and the nitrate electrocatalytic reduction reaction due to substantial coordinately unsaturated active sites, a high surface area, and available mass transfer pathways. Consequently, the CoP NRs can achieve a faradaic efficiency of 97.1% towards NO3--to-NH3 conversion and provide an NH3 yield of 30.1 mg h-1 mg-1cat at a -0.5 V potential.

Ultrahigh-Uptake Capacity-Enabled Gas Separation and Fruit Preservation by a New Single-Walled Nickel-Organic Framework.

High gas-uptake capacity is desirable for many reasons such as gas storage and sequestration. Moreover, ultrahigh capacity can enable a practical separation process by mitigating the selectivity factor that sometimes compromises separation efficiency. Herein, a single-walled nickel-organic framework with an exceptionally high gas capture capability is reported. For example, C2H4 and C2H6 uptake capacities are at record-setting levels of 224 and 289 cm3 g-1 at 273 K and 1 bar (169 and 110 cm3 g-1 at 298 K and 1 bar), respectively. Such ultrahigh capacities for both gases give rise to an excellent separation performance, as shown for C2H6/C2H4 with breakthrough times of 100, 60 and 30 min at 273, 283 and 298 K and under 1 atm. This new material is also shown to readily remove ethylene released from fruits, and once again, its ultrahigh capacity plays a key role in the extraordinary length of time achieved in the preservation of the fruit freshness.

Precise Pore Space Partitions Combined with High-Density Hydrogen-Bonding Acceptors within Metal-Organic Frameworks for Highly Efficient Acetylene Storage and Separation.

The high storage capacity versus high selectivity trade-off barrier presents a daunting challenge to practical application as an acetylene (C2 H2 ) adsorbent. A structure-performance relationship screening for sixty-two high-performance metal-organic framework adsorbents reveals that a moderate pore size distribution around 5.0-7.5 Šis critical to fulfill this task. A precise pore space partition approach was involved to partition 1D hexagonal channels of typical MIL-88 architecture into finite segments with pore sizes varying from 4.5 Š(SNNU-26) to 6.4 Š(SNNU-27), 7.1 Š(SNNU-28), and 8.1 Š(SNNU-29). Coupled with bare tetrazole N sites (6 or 12 bare N sites within one cage) as high-density H-bonding acceptors for C2 H2 , the target MOFs offer a good combination of high C2 H2 /CO2 adsorption selectivity and high C2 H2 uptake capacity in addition to good stability. The optimized SNNU-27-Fe material demonstrates a C2 H2 uptake of 182.4 cm3 g-1 and an extraordinary C2 H2 /CO2 dynamic breakthrough time up to 91 min g-1 under ambient conditions.

Tuning the Pore Surface of an Ultramicroporous Framework for Enhanced Methane and Acetylene Purification Performance.

Both methane (CH4) and acetylene (C2H2) are important energy source and raw chemicals in many industrial processes. The development of an energy-efficient and environmentally friendly separation and purification strategy for CH4 and C2H2 is necessary. Ultramicroporous metal-organic framework (MOF) materials have shown great success in the separation and purification of small-molecule gases. Herein, the synergy effect of tritopic polytetrazolate and ditopic terephthalate ligands successfully generates a series of isoreticular ultramicroporous cadmium tetrazolate-carboxylate MOF materials (SNNU-13-16) with excellent CH4 and C2H2 purification performance. Except for the uncoordinated tetrazolate N atoms serving as Lewis base sites, the pore size and pore surface of MOFs are systematically engineered by regulating dicarboxylic acid ligands varying from OH-BDC (SNNU-13) to Br-BDC (SNNU-14) to NH2-BDC (SNNU-15) to 1,4-NDC (SNNU-16). Benefiting from the ultramicroporous character (3.8-5.9 Å), rich Lewis base N sites, and tunable pore environments, all of these ultramicroporous MOFs exhibit a prominent separation capacity for carbon dioxide (CO2) or C2 hydrocarbons from CH4 and C2H2. Remarkably, SNNU-16 built by 1,4-NDC shows the highest ideal adsorbed solution theory CO2/CH4, ethylene (C2H4)/CH4, and C2H2/CH4 separation selectivity values, which are higher than those of most famous MOFs with or without open metal sites. Dynamic breakthrough experiments show that SNNU-16 can also efficiently separate the C2H2/CO2 mixtures with a gas flow rate of 4 mL min-1 under 1 bar and 298 K. The breakthrough time (18 min g-1) surpasses most best-gas-separation MOFs and nearly all other metal azolate-carboxylate MOF materials under the same conditions. The above prominently CH4 and C2H2 purification abilities of SNNU-13-16 materials were further confirmed by the Grand Canonical Monte Carlo (GCMC) simulations.

Tailoring the Pore Environment of a Robust Ga-MOF by Deformed [Ga3O(COO)6] Cluster for Boosting C2H2 Uptake and Separation.

The construction of superstable metal-organic frameworks (MOFs) for selective gas uptake is urgently demanded but remains a great challenge. Herein, a unique bifunctional deformed [Ga3O(COO)6] inorganic secondary building unit (SBU) generated from the desymmetrical evolution of typical triangular prismatic trinuclear cluster was first introduced, which was extended by an isosceles triangular organic linker to produce a robust Ga-MOF (SNNU-63). Remarkably, SNNU-63 can stabilize in water at 25 °C for 96 h and at 80 °C for more than 24 h, which surpasses nearly all other Ga-MOFs. The combined effects of open metal sites and hydrophobic pore environment provided by deformed [Ga3O] SBUs render SNNU-63 with high C2H2 storage capacity and efficient C2H2 and natural gas purification performance. The ideal adsorbed solution theory calculation, column breakthrough tests, and grand canonical Monte Carlo simulations demonstrate that SNNU-63 is a potential material for addressing the challenge of C2H2/CO2 and C2H2/CH4 mixture separation under ambient conditions.

Systematic Regulation of C2H2/CO2 Separation by 3p-Block Open Metal Sites in a Robust Metal-Organic Framework Platform.

The separation of a mixture of C2H2 and CO2 is a great challenge due to their similar molecular sizes and shapes. Al-based metal-organic frameworks (Al-MOFs) have great promise for gas separation applications due to their light weight, high stability, and low cost. However, the cultivation of suitable Al-MOF single crystals is extremely difficult and has limited their explorations up to now. Since In, Ga, and Al are all 3p-block metal elements, a systematic application of the periodic law to investigate 3p-MOFs will undoubtedly help in the understanding and development of worthy Al-MOF materials. Herein, we report the design of a robust 3p metal-organic framework platform (SNNU-150) and the systematic regulation of C2H2/CO2 separation by open 3p-block metal sites. X-ray single-crystal diffraction analysis reveals that SNNU-150 is a 3,6-connected 3D framework consisting of [M3O(COO)6] trinuclear secondary building units (SBUs) and tritopic nitrilotribenzoate (NTB) linkers. Small {[M3O(COO)6]4(NTB)6} tetrahedral cages and extra-large {[M3O(COO)6]10(NTB)14} polyhedral cages connect with each other to generate a hierarchically porous architecture. These 3p-MOFs present very high water, thermal, and chemical stability, especially for SNNU-150-Al, which can maintain its framework at 85 °C in water for 24 h and in a room-temperature environment for more than 30 days. IAST calculations, breakthrough experiments, and GCMC simulations all show that SNNU-150 MOFs have top-level C2H2/CO2 separation performance and follow the order Al-MOF > Ga-MOF > In-MOF.

Mimic of Ferroalloy To Develop a Bifunctional Fe-Organic Framework Platform for Enhanced Gas Sorption and Efficient Oxygen Evolution Electrocatalysis.

It is well-known that the formation of ferroalloy with the addition of the second or third metal during the steel-making process usually can improve the performance of the iron. Inspired by ferroalloy materials, it is speculated that the pore environment, framework charge, and catalytic properties of metal-organic frameworks (MOFs) could be optimized dramatically via the introduction of ferroalloy-like inorganic building blocks. However, different to ferroalloy, the accurate integration of different metals into one MOF platform is still challenging. Herein, taking advantages of the good compatibility for metals in trigonal prismatic trinuclear cluster, a series of Fe-based alloy-like [M3O(O2C)6] motifs (M3 = Fe3, Fe1.5Ni1.5, Fe1.5Co1.5, Fe1.5Ti1.5, FeCoNi, and FeTiCo) are successfully generated, which further lead to a robust Fe-MOF material family (SNNU-5s). These multicomponent MOFs not only provide a good chance to explore the impact of pore environment on gas adsorption/separation but also offer an opportunity to the efficient electrocatalytic reaction directly. Accordingly, compared with the SNNU-5-Fe parent structure, the pore characters of heterometallic SNNU-5 MOFs are clearly regulated by the type of alloy-like building blocks. SNNU-5-FeTi displays more superior gas separation performance for CO2/CH4, C2H2/CH4, C2H4/CH4, and C2H2/CO2 gas mixtures. What is more, benefited from the multimetallic active sites and their catalytic synergy, FeCoNi-ternary alloy-like cluster-based SNNU-5 MOF material exhibits an exceptional oxygen evolution reaction activity in aqueous solution at pH = 13, which delivers a low overpotential (ηj=10 = 317 mV), a fast reaction kinetics (Tafel slope = 37 mV dec-1), and excellent catalytic stability. This facile multialloy-like building block strategy holds promise to accurately design and improve the performance of MOFs, as well as open an avenue to understand the related mechanisms.

Topology-Guided Design for Sc-soc-MOFs and Their Enhanced Storage and Separation for CO2 and C2-Hydrocarbons.

Evaluating the effect of ligand substitution on metal ions and/or clusters during the MOF growth process is conducive to rational design of isoreticular MOFs with improved performance. Through topological direction and ligand substitution strategy, we herein constructed two Sc-soc-MOFs (Sc-EBTC and Sc-ABTC) based on two similar rectangular-planar diisophthalate ligands, linear-shaped H4EBTC (1,1'-ethynebenzene-3,3',5,5'-tetracarboxylic acid) and zigzag-shaped H4ABTC (3,3',5,5'-azobenzenetetracarboxylic acid), under solvothermal conditions with formic acid as a modulator. {Sc[(Sc3O)(H2O)3]3(EBTC)6} (Sc-EBTC) possesses two distinct clusters as SBUs, trinuclear [Sc3O(CO2)6] (SBU1) and mononuclear cluster [ScO6] (SBU2), which maintain the soc-topology except for the mononuclear [ScO6] instead of the corresponding trinuclear [Sc3O(CO2)6] in Sc-ABTC ({(Sc3O)(H2O)3(ABTC)1.5(NO3)}). Notably, Sc-EBTC represents a rare soc-MOF with two distinct clusters as SBUs. Due to similar pore spaces, the two Sc-soc-MOF materials both exhibit enhanced and comparable gas sorption and selectivity performances. Specially, their remarkable C2H2, C2H4, and CO2 storage capacity along with prominent CO2/CH4 and C2-hydrocarbons/CH4 separations indicate that these Sc-soc-MOFs are promising adsorbents for natural gas purification under ambient conditions.

Ultramicroporous Building Units as a Path to Bi-microporous Metal-Organic Frameworks with High Acetylene Storage and Separation Performance.

A strategy called ultramicroporous building unit (UBU) is introduced. It allows the creation of hierarchical bi-porous features that work in tandem to enhance gas uptake capacity and separation. Smaller pores from UBUs promote selectivity, while larger inter-UBU packing pores increase uptake capacity. The effectiveness of this UBU strategy is shown with a cobalt MOF (denoted SNNU-45) in which octahedral cages with 4.5 Špore size serve as UBUs. The C2 H2 uptake capacity at 1 atm reaches 193.0 cm3 g-1 (8.6 mmol g-1 ) at 273 K and 134.0 cm3 g-1 (6.0 mmol g-1 ) at 298 K. Such high uptake capacity is accompanied by a high C2 H2 /CO2 selectivity of up to 8.5 at 298 K. Dynamic breakthrough studies at room temperature and 1 atm show a C2 H2 /CO2 breakthrough time up to 79 min g-1 , among top-performing MOFs. Grand canonical Monte Carlo simulations agree that ultrahigh C2 H2 /CO2 selectivity is mainly from UBU ultramicropores, while packing pores promote C2 H2 uptake capacity.

Highly Selective and Sensitive Turn-Off-On Fluorescent Probes for Sensing Al3+ Ions Designed by Regulating the Excited-State Intramolecular Proton Transfer Process in Metal-Organic Frameworks.

The concept of high-performance excited-state intramolecular proton transfer (ESIPT)-based fluorescent metal-organic framework (MOF) probes for Al3+ is proposed in this work. By regulating the hydroxyl groups on the organic linker step by step, new fluorescent magnesium-organic framework (Mg-MOF) probes for Al3+ ions were established based on the ESIPT fluorescence mechanism. It is observed for the first time that the number of intramolecular hydrogen bonds between adjacent hydroxyl and carboxyl groups can effectively adjust the ESIPT process and lead to tunable fluorescence sensing performance. Together with the well-designed porous and anionic framework, the Mg-TPP-DHBDC probe decorating with a pair of intramolecular hydrogen bonds exhibits extra-high quantitative fluorescence response to Al3+ through an unusual turn-off (0-1.2 µM) and turn-on (4.2-15 µM) luminescence sensing mechanism. Notably, the 28 nM limit of detection value represents the lowest record among all reported MOF-based Al3+ fluorescent sensors up to now. Benefited from the unique turn-off-on ESIPT fluorescence detection process, the Mg-TPP-DHBDC MOF sensor exhibits single Al3+ detection compared with other 16 common metal ions including Ga3+, In3+, Fe3+, Cr3+, Ca2+, and Mg2+. Impressively, such an Al3+ selective sensing process can even be fulfilled by the reusable MOF test paper detected by naked eyes. Overall, the quantitative Al3+ detection, together with the extraordinary sensitivity, selectivity, fast response, and good reusability, strongly supports our concept of ESIPT-based fluorescent MOF Al3+ probes and makes Mg-TPP-DHBDC one of the most powerful Al3+ fluorescent sensors.

Design of High-Symmetrical Magnesium-Organic Frameworks with Acetate as Modulator and Their Fluorescence Sensing Performance.

During the formation of magnesium-organic frameworks, the coordination sphere of magnesium tends to be partially occupied by O-containing solvent molecules such as amides, which will dramatically decrease the symmetry of Mg-organic frameworks and thus lead to low stability. It is noted that up to now, most reported Mg-metal-organic frameworks (MOFs) (>80%) crystallize in the space groups whose symmetry is lower than that of a tetragonal system. In this work, we demonstrate that acetate (Ac) may act as modulator to eliminate the influence of amide solvent and improve the symmetry of Mg-organic frameworks. Two novel Mg-MOFs, namely, {[(CH3)NH3]4[Mg3(BTB)8/3(Ac)2(H2O)]} n (SNNU-35, H3BTB = 4',4'',4'''-benzene-1,3,5-tribenzoic acid) and {[(CH3)2NH2][Mg2(FDA)2(Ac)]} n (SNNU-36, H2FDA = 2,5-furandicarboxylic acid) were successfully designed, which crystallize in rhombohedral R-3 and tetragonal I4 /mmm space groups, respectively. Four independent BTB ligands link three unique Mg cations and generate superlarge [Mg21BTB17] nanocages, which interlock each other by strong π···π stacking to give a two-fold interpenetrating architecture of SNNU-35. On the other hand, carboxylate and acetate groups chelate Mg atoms to form one-dimensional chains, which are extended by FDA to produce the rod-packing framework of SNNU-36. Two microporous Mg-MOFs both exhibit notable CO2 and H2 uptakes. H3BTB and H2FDA ligands both have emission features, and Mg ions usually can enhance the fluorescent intensity, which lead to a strong solid-state luminescence emission property of SNNU-35 and -36. Importantly, two Mg-MOFs both show fast and quantative sensing performance for nitrocompounds. Among three selected models of substrate, SNNU-35 and -36 can eliminate the interference of nitromethane (NM) and exhibit high sensitivity to nitrobenzene (NB) and o-nitrotoluene (2-NT) with large k sv values (>105 M-1). Especially, the fluorescence quenching efficiency of NB (5000 ppm) and 2-NT (8000 ppm) can reach 96.3% and 89.5% and 85.0% and 83.7% for SNNU-35 and -36, respectively. This work offers not only an effective route to improve the symmetry of magnesium-organic frameworks but also two potential fluorescence sensors for nitroaromatic compounds.

A semiconductor and fluorescence dual-mode room-temperature ammonia sensor achieved by decorating hydroquinone into a metal-organic framework.

Presented herein is a magnesium-organic framework (SNNU-88) incorporated with active hydroquinone groups, which exhibits not only remarkable semiconductor sensing for traces of ammonia vapor (5-100 ppm), but also extra-high fluorescence response to liquid NH3·H2O through an unusual turn-off (0-1.5 ppm) and turn-on (3.0-100 ppm) luminescence sensing mechanism at room temperature. Such bifunctional quantitative ammonia detection together with the extraordinary sensitivity and selectivity, fast response, and good reusability makes SNNU-88 one of the most powerful ammonia sensors.

Assembly of [Cu2(COO)4] and [M3(µ3-O)(COO)6] (M = Sc, Fe, Ga, and In) building blocks into porous frameworks towards ultra-high C2H2/CO2 and C2H2/CH4 separation performance.

A porous MOF platform (SNNU-65s) formed by creatively combining paddle-wheel-like [Cu2(COO)4] and trigonal prismatic [M3(µ3-O)(COO)6] building blocks was designed herein. The mixed and high-density open metal sites and the OH-functionalized pore surface promote SNNU-65s to exhibit ultra-high C2H2 uptake and separation performance. Impressively, SNNU-65-Cu-Ga stands out for the highest C2H2/CO2 (18.7) and C2H2/CH4 (120.6) selectivity among all the reported MOFs at room temperature.

Atoms diffusion-induced phase engineering of platinum-gold alloy nanocrystals with high electrocatalytic performance for the formic acid oxidation reaction.

Bimetallic noble metal nanocrystals have been widely applied in many fields, which generally are synthesized by the wet-chemistry reduction method. This work presents a purposely designed atoms diffusion induced phase engineering of PtAu alloy nanocrystals on platy Au substrate (PtAu-on-Au nanostructures) through simple hydrothermal treatment. Benefitting from the synergistic effects of component and structure, PtAu-on-Au nanostructures remarkably enhance the dehydrogenation pathway of the formic acid oxidation reaction (FAOR), and thus exhibit much higher FAOR activity and durability compared with Pt nanocrystals on platy Au substrate (Pt-on-Au nanostructures) and commercial Pd black due to an excellent stability of platy Au substrate and a high oxidation resistance of PtAu alloy nanocrystals. The atoms diffusion-induced phase engineering demonstrated in this work builds a bridge between the traditional metallurgy and modern nanotechnologies, which also provides some useful insights in developing noble metals based alloyed nanostructures for the energy and environmental applications.

Ionothermal Design of Crystalline Halogeno(cyano)cuprate Family: Structure Diversity, Solid-State Luminescence, and Photocatalytic Performance.

A general preparative method for multifunctional halogeno(cyano)cuprate materials in ionic liquids is developed in this work. Under ionothermal conditions, alkylimidazolium-based ionic liquids serving as solvent, charge-compensating, and structure-directing agent, as well as reactant lead to 12 members of the novel hybrid halogeno(cyano)cuprate family with a general formula of [R1R2R3IM]b+c-a[CuaXb(CN)c] (R1R2R3IM = alkylimidazolium cations, X = halide anions). X-ray single-crystal diffractions show that diverse inorganic halogeno(cyano)cuprate components vary from discrete complexes (1 and 2), one-dimensional (1D) chains (3-7), two-dimensional (2D) layer (8), to three-dimensional (3D) open frameworks (9-12). 1 and 2 are of zero-dimensional discrete structures containing triangular [CuX3]2- anions. In complexes 3-7, pentagonal bipyramidal [Cu2X3] units are bridged by CN groups to give 1D [Cu2X3(CN)]2- inorganic chains, which are charge-balanced by the surrounded alkylimidazolium cations. 2D inorganic [Cu5ClI2(CN)4]2- layer in complex 8 is alternately packed with [VMIM]+ organic cations. In complex 9, left- and right-handed Cu-CN helical chains connect each other to give a 3D open framework, which are further entrapped by 1D zigzag Cu-CN chains and [PMIM]+ cations. Diverse unique Cu(I) atoms and cyanide or halide bridging groups in 10, 11, and 12 are extended into 3D anionic open frameworks with 1D channels, which are occupied by alkylimidazolium cations. For all hybrid halogeno(cyano)cuprate complexes, the extensively existing C-H···X or C-H···π hydrogen bonds help to stabilize the ultimate supramolecular packing structures. Notably, the distances between adjacent Cu(I) centers range from 2.420(2) to 2.989(2) Å in all polymeric frameworks, which indicate strong Cu···Cu interactions. Thanks to the cooperation of conjugate π electron cyanide systems with halide ions and/or Cu···Cu interactions, compounds 1-12 all demonstrate strong solid-state photoluminescence and semiconducting performance. Specially, hybrid halogeno(cyano)cuprates reported herein first exhibit excellent photocatalytic degradation of organic dye. To the best of our knowledge, fewer than 10 crystalline halogeno(cyano)cuprate compounds were obtained before this work, although different synthetic routes have been involved. Clearly, the discovery of this large hybrid material family under ionothermal conditions is important for the further development of novel functional halogeno(cyano) filled-shell d10 metal crystalline materials.

Ligand Torsion Triggered Two Robust Fe-Tetratopic Carboxylate Frameworks with Enhanced Gas Uptake and Separation Performance.

By regulating the tetratopic carboxylate ligands, two robust Fe-MOFs (MOF=Metal-organic framework) comprising trigonal prismatic building blocks under a DMA/DMSO/HBF4 solvent system, namely, [(CH3 )2 NH2 ][FeII3 (OH)(BPTC)1.5 (DMSO)3 ] (SNNU-60) and [FeIII FeII2 (OH)(ABTC)1.5 (DMSO)3 ] (SNNU-61) (BPTC=3,3',5,5'-biphenyltetracarboxylic acid, ABTC=3,3',5,5'-azobenzenetetracarboxylic acid, SNNU=Shaanxi Normal University) have been successfully synthesized. The torsions between the benzene groups of the ligands result in two MOFs exhibiting completely different (4,6)-connected frameworks, which represent the only two MOF types constructed by [M3 (O/OH)(COO)6 ] trimeric building units and quadrilateral tetratopic carboxylate linkers until now. The robust Fe-MOFs SNNU-60 and SNNU-61 both exhibit high thermal/chemical stability, permanent microporosity, and excellent gas uptake capability for H2 , CO2 , C2 H2 , and C2 H4 under 1 bar. SNNU-60 in particular displays very high C2 H2 capture under low pressure (85 cm3 cm-3 at 0.15 bar and 298 K), which is among the top C2 H2 uptake MOF materials. Also, these two Fe-MOFs display high separation for CO2 and C2 -hydrocarbons over CH4 . Significantly, thanks to the high stability, suitable pore size, open Fe sites, and ion skeleton, SNNU-60 has extremely high C2 H2 /CH4 selectivity (83.6, 298 K), which surpasses most MOFs reported so far under the same conditions.