Tailorable Synthesis of Porous Organic Polymers Decorating Ultrafine Palladium Nanoparticles for Hydrogenation of Olefins

Two 1,2,3-triazolyl-containing porous organic polymers (CPP-C and CPP-Y) were readily synthesized through click reaction and Yamamoto coupling reaction, respectively. The effects of synthetic methods on the structures and properties of CPP-C and CPP-Y were investigated. Their chemical compositions are almost identical, but their physical and texture properties are different from each other. Ultrafine palladium nanoparticles can be effectively immobilized in the interior cavities of CPP-C and CPP-Y. The interactions between polymers and palladium are verified by IR, solid-state NMR, XPS, and EDS. Their catalytic performances are evaluated by hydrogenation of olefins. Pd@CPP-Y exhibits higher catalytic activity and recyclability than Pd@CPP-C. Hot filtration and the three-phase test indicate that hydrogenation functions in a heterogeneous pathway

Facile Fabrication of Ultrafine Palladium Nanoparticles with Size- and Location-Control in Click-Based Porous Organic Polymers

Two click-based porous organic polymers (CPP-1 and CPP-2) are readily synthesized through a click reaction. Using CPP-1 and CPP-2 as supports, palladium nanoparticles (NPs) with uniform and dual distributions were prepared through H₂ and NaBH₄ reduction routes, respectively. Ultrafine palladium NPs are effectively immobilized in the interior cavities of polymers. The coordination of 1,2,3-triazolyl to palladium and the confinement effect of polymers on palladium NPs are verified by solid-state ¹³C NMR and IR spectra, XPS analyses, EDX mapping, and computational calculation. The steric and electronic properties of polymers have a considerable influence on the interaction between polymers and palladium NPs, as well as the catalytic performances of NPs. The ultrafine palladium NPs with uniform distribution exhibit superior stability and recyclability over palladium NPs with dual distributions and palladium on charcoal in the hydrogenation of nitroarenes, and no obvious agglomeration and loss of catalytic activity were observed after recycling several times. The excellent performances mainly result from synergetic effects between palladium NPs and polymers

Anion-Directed Assemblies of Cationic Metal–Organic Frameworks Based on 4,4′-Bis(1,2,4-triazole): Syntheses, Structures, Luminescent and Anion Exchange Properties

Three cationic metal–organic frameworks (MOFs), Ag­(btr)·​PF₆·​0.5CH₃CN (<b>1</b>), Ag₂(btr)₂­(H₂O)·​2CF₃SO₃·​H₂O (<b>2</b>), and Ag₂(btr)₂­(NO₃)·​NO₃ (<b>3</b>), were prepared from reaction of 4,4′-bis­(1,2,4-triazole) (btr) with silver salts containing different anions. Complex <b>1</b> is a three-dimensional (3-D) framework constructed from tetrahedral-shaped nanoscale coordination cages with PF₆^– as counteranions. <b>2</b> and <b>3</b> are 3-D architectures containing 1-D channels, in which charge-balancing CF₃SO₃^– and NO₃^– are located in their respective channels. Luminescent emission of <b>1</b>–<b>3</b> shows an obvious red shift compared with the btr ligand. Anion exchange studies show that <b>1</b> is able to selectively exchange MnO₄^– in aqueous solution with a modest capacity of 0.56 mol mol^–1; the luminescent emission of <b>1</b> is quickly quenched upon MnO₄^– exchange

Additive-Free Hydrogen Generation from Formic Acid Boosted by Amine-Functionalized Imidazolium-Based Ionic Polymers

Catalytic dehydrogenation of formic acid (FA) is an efficient approach to store and release hydrogen in fuel-cell-based hydrogen economy; it is still a daunting challenge to the design and synthesis of the additive-free heterogeneous catalytic systems. In this contribution, we present an amine-functionalized main-chain imidazolium-based ionic polymer (ImIP-1) for boosting additive-free hydrogen generation from FA. The ultrafine palladium nanoparticles (NPs) with uniform dispersion over ImIP-1 were readily obtained through simple anion exchange between chloride in ImIP-1 and tetrachloropalladate and subsequent reduction with NaBH₄. The palladium NPs are synergetically stabilized by coordination interaction and electrostatic effect from ImIP-1. The amine groups in the host backbone of ImIP-1 serve as basic sites to accelerate the cleavage of O–H bond in FA. The catalytic system shows outstanding catalytic activity, high stability, and excellent recyclability in additive-free heterogeneous FA dehydrogenation under mild conditions. The initial TOF values at 50 and 25 °C are as high as 1593 and 356 h^–1, respectively, which are 10 times higher than those in its counterpart without amine groups. The impressive catalytic performance ranks it among the state-of-the-art of those in heterogeneous catalytic systems based on supported palladium NPs

Imidazolium-Based Porous Organic Polymers: Anion Exchange-Driven Capture and Luminescent Probe of Cr₂O₇^2–

A series of imidazolium-based porous organic polymers (POP-Ims) was synthesized through Yamamoto reaction of 1,3-bis­(4-bromophenyl)­imidazolium bromide and tetrakis­(4-bromophenyl)­ethylene. Porosities and hydrophilicity of such polymers may be well tuned by varying the ratios of two monomers. POP-Im with the highest density of imidazolium moiety (POP-Im1) exhibits the best dispersity in water and the highest efficiency in removing Cr₂O₇^2–. The capture capacity of 171.99 mg g^–1 and the removal efficiency of 87.9% were achieved using an equivalent amount of POP-Im1 within 5 min. However, no Cr₂O₇^2– capture was observed using nonionic analogue despite its large surface area and abundant pores, suggesting that anion exchange is the driving force for the removal of Cr₂O₇^2–. POP-Im1 also displays excellent enrichment ability and remarkable selectivity in capturing Cr₂O₇^2–. Cr­(VI) in acid electroplating wastewater can be removed completely using excess POP-Im1. In addition, POP-Im1 can serve as a luminescent probe for Cr₂O₇^2– due to the incorporation of luminescent tetraphenylethene moiety

Highly Conductive Porous Transition Metal Dichalcogenides via Water Steam Etching for High-Performance Lithium–Sulfur Batteries

Lithium–sulfur (Li–S) batteries show significant advantages for next-generation energy storage systems owing to their high energy density and cost effectiveness. The main challenge in the development of long-life and high-performance Li–S batteries is to simultaneously facilitate the redox kinetics of sulfur species and suppress the shuttle effect of polysulfides. In this contribution, we present a general and green water-steam-etched approach for the fabrication of H- and O-incorporated porous TiS₂ (HOPT). The conductivity, porosity, chemisorptive capability, and electrocatalytic activity of HOPT are enhanced significantly when compared with those of raw TiS₂. The synthetic method can be expanded to the fabrication of other highly conductive transition metal dichalcogenides such as porous NbS₂ and CoS₂. The as-obtained HOPT can serve as both a substitute of conductive agents and an additive of interlayer materials. The optimal electrode delivers discharge capacities of 950 mA h g^–1 after 300 cycles at 0.5 C and 374 mA h g^–1 after 1000 cycles at 10 C. Impressively, an unprecedented reversible capacity of 172 mA h g^–1 is achieved after 2500 cycles at 30 C, and the average capacity fading rate per cycle is as low as 0.015%. Importantly, four half-cells based on this electrode in series could drive 60 light-emitting diode indicator modules (the nominal power 3 W) after 20 s of charging. The instantaneous current and power of this device on reaching 275 A g^–1 and 2611 W g^–1, respectively, indicate outstanding high-power discharge performance and potential applications in electric vehicles and other large-scale energy storage systems

Nanohybrid of Carbon Quantum Dots/Molybdenum Phosphide Nanoparticle for Efficient Electrochemical Hydrogen Evolution in Alkaline Medium

The exploration of highly efficient non-noble metal electrocatalysts for hydrogen evolution reaction (HER) under alkaline conditions is highly imperative but still remains a great challenge. In this work, the nanohybrid of carbon quantum dots and molybdenum phosphide nanoparticle (CQDs/MoP) has been firstly demonstrated as an efficient alkaline HER electrocatalyst. The CQDs/MoP nanohybrid is readily prepared through a charge-directed self-assembly of CQDs with phosphomolybdic acid (H₃PMo₁₂O₄₀) at the molecular level, followed by facile phosphatizing at 700 °C. The introduction of CQDs greatly helps to alleviate the agglomeration and surface oxidation of MoP nanoparticles and ensures each MoP nanoparticle to be electronically addressed, thus significantly enhancing the intrinsic catalytic activity of MoP. The optimized CQDs/MoP exhibits high-efficiency synergistic catalysis toward HER in 1 M KOH electrolyte with a low onset potential of −0.08 V and a small Tafel slope of 56 mV dec^–1 as well as high durability with negligible current loss for at least 24 h

Sandwich-Type NbS₂@S@I-Doped Graphene for High-Sulfur-Loaded, Ultrahigh-Rate, and Long-Life Lithium–Sulfur Batteries

Lithium–sulfur batteries practically suffer from short cycling life, low sulfur utilization, and safety concerns, particularly at ultrahigh rates and high sulfur loading. To address these problems, we have designed and synthesized a ternary NbS₂@S@IG composite consisting of sandwich-type NbS₂@S enveloped by iodine-doped graphene (IG). The sandwich-type structure provides an interconnected conductive network and plane-to-point intimate contact between layered NbS₂ (or IG) and sulfur particles, enabling sulfur species to be efficiently entrapped and utilized at ultrahigh rates, while the structural integrity is well maintained. NbS₂@S@IG exhibits prominent high-power charge/discharge performances. Reversible capacities of 195, 107, and 74 mA h g^–1 (1.05 mg cm^–2) have been achieved after 2000 cycles at ultrahigh rates of 20, 30, and 40 C, respectively, and the corresponding average decay rates per cycle are 0.022%, 0.031% and 0.033%, respectively. When the area sulfur loading is increased to 3.25 mg cm^–2, the electrode still maintains a high discharge capacity of 405 mAh g^–1 after 600 cycles at 1 C. Three half-cells in series assembled with NbS₂@S@IG can drive 60 indicators of LED modules after only 18 s of charging. The instantaneous current and power of the device reach 196.9 A g^–1 and 1369.7 W g^–1, respectively

Structure–Activity Relationships of AMn₂O₄ (A = Cu and Co) Spinels in Selective Catalytic Reduction of NO_<i>x</i>: Experimental and Theoretical Study

CuMn₂O₄ and CoMn₂O₄ spinels were facilely synthesized by oxidation–precipitation and subsequent heat treatment at relatively low temperature. Selective catalytic reduction (SCR) of NO_<i>x</i> demonstrates that NO_<i>x</i> conversions in CuMn₂O₄ with (111) plane (CuMn₂O₄-C) and in CuMn₂O₄-C with (311) plane (CuMn₂O₄-T) are more than 90% at 200 and 300 °C, respectively, which are superior to those in CoMn₂O₄-C and CoMn₂O₄-T. CuMn₂O₄-C and CoMn₂O₄-C exhibit higher absorption amounts of NH₃/NO and more oxygen vacancies than CuMn₂O₄-T and CoMn₂O₄-T, respectively. In addition, CuMn₂O₄-C displays high catalytic activity and good stability in NH₃-SCR in the presence of 100 ppm of SO₂ and 10 vol % H₂O. In situ diffuse reflection infrared Fourier transform spectroscopy results indicate the coexistence of Eley–Rideal and Langmuir–Hinshelwood mechanisms in CuMn₂O₄-C, and the Eley–Rideal mechanism is predominant

General Synthetic Route toward Highly Dispersed Ultrafine Pd–Au Alloy Nanoparticles Enabled by Imidazolium-Based Organic Polymers

Bimetallic Pd–Au nanoparticles (NPs) usually show superior catalytic performances over their single-component counterparts, the general and facile synthesis of subnanometer-scaled Pd–Au NPs still remains a great challenge, especially for electronegative ultrafine bimetallic NPs. Here, we develop an anion-exchange strategy for the synthesis of ultrafine Pd–Au alloy NPs. Simple treatment of main-chain imidazolium-based organic polymer (IOP) with HAuCl₄ and Na₂PdCl₄, followed by reduction with NaBH₄ generated Pd–Au alloy NPs (Pd–Au/IOP). These NPs possess an unprecedented tiny size of 1.50 ± 0.20 nm and are uniformly dispersed over IOP. The electronic structure of the surface Pd and Au atoms is optimized via electron exchange during alloying, a net charge flowing resulting from counteranions is injected into Au and Pd to form a strong ensemble effect, which is responsible for a remarkably higher catalytic activity of Pd–Au/IOP in the hydrolytic dehydrogenation of ammonia borane than those of monometallic counterparts