A Series of (6,6)-Connected Porous Lanthanide−Organic Framework Enantiomers with High Thermostability and Exposed Metal Sites: Scalable Syntheses, Structures, and Sorption Properties

A series of microporous lanthanide−organic framework enantiomers, Ln(BTC)(H2O)·(DMF)1.1 (Ln = Y 1a, 1b; Tb 2a, 2b; Dy 3a, 3b; Er 4a, 4b; Yb 5a, 5b, BTC = 1,3,5-benzenetricarboxylate; DMF = N,N-dimethylformamide) with unprecedented (6,6)-connected topology have been prepared and characterized. All these compounds exhibit very high thermal stability of over 450 °C. The pore characteristics and gas sorption properties of these compounds were investigated at cryogenic temperatures by experimentally measuring nitrogen, argon, and hydrogen adsorption/desorption isotherms. The studies show that all these compounds are highly porous with surface areas of 1080 (1), 786 (2), 757 (3), 676 (4), and 774 m2/g (5). The amounts of the hydrogen uptakes, 1.79 (1), 1.45 (2), 1.40 (3), 1.51 (4), and 1.41 wt % (5) at 77 K (1 atm), show their promising H2 storage performances. These porous materials with considerable surface areas, high voids of 44.5% (1), 44.8% (2), 47.7% (3), 44.2% (4), and 45.7% (5), free windows of 6−7 Å, available exposed metal sites and very high thermal stability can be easily prepared on a large scale, which make them excellent candidates in many functional applications, such as, gas storage, catalysis, and so on

A Series of (6,6)-Connected Porous Lanthanide−Organic Framework Enantiomers with High Thermostability and Exposed Metal Sites: Scalable Syntheses, Structures, and Sorption Properties

A series of microporous lanthanide−organic framework enantiomers, Ln(BTC)(H2O)·(DMF)1.1 (Ln = Y 1a, 1b; Tb 2a, 2b; Dy 3a, 3b; Er 4a, 4b; Yb 5a, 5b, BTC = 1,3,5-benzenetricarboxylate; DMF = N,N-dimethylformamide) with unprecedented (6,6)-connected topology have been prepared and characterized. All these compounds exhibit very high thermal stability of over 450 °C. The pore characteristics and gas sorption properties of these compounds were investigated at cryogenic temperatures by experimentally measuring nitrogen, argon, and hydrogen adsorption/desorption isotherms. The studies show that all these compounds are highly porous with surface areas of 1080 (1), 786 (2), 757 (3), 676 (4), and 774 m2/g (5). The amounts of the hydrogen uptakes, 1.79 (1), 1.45 (2), 1.40 (3), 1.51 (4), and 1.41 wt % (5) at 77 K (1 atm), show their promising H2 storage performances. These porous materials with considerable surface areas, high voids of 44.5% (1), 44.8% (2), 47.7% (3), 44.2% (4), and 45.7% (5), free windows of 6−7 Å, available exposed metal sites and very high thermal stability can be easily prepared on a large scale, which make them excellent candidates in many functional applications, such as, gas storage, catalysis, and so on

Immobilizing Extremely Catalytically Active Palladium Nanoparticles to Carbon Nanospheres: A Weakly-Capping Growth Approach

Ultrafine palladium nanoparticles (Pd NPs) supported on carbon nanospheres have been successfully synthesized using a facile methanol-mediated weakly-capping growth approach (WCGA) with anhydrous methanol as a mild reductant and a weakly capping agent. The Pd NPs show exceedingly high catalytic activity for 100% selective dehydrogenation of aqueous formic acid (FA) at ambient temperatures. The small size and clean surface of the Pd NPs greatly improve the catalytic properties of the as-prepared catalyst, providing an average rate of CO-free H₂ generation up to 43 L H₂ g_Pd^–1 min^–1 and a turnover frequency of 7256 h^–1 at 60 °C. These values are much higher than those obtained even with the most active catalyst reported thus far for heterogeneously catalyzed dehydrogenation of FA. This remarkably facile and effective methanol-mediated WCGA provides a powerful entry into ultrafine metal NPs with clean surface to achieve enhanced performance. Moreover, the catalytic results open up new avenues in the effective applications of FA for hydrogen storage

Immobilizing Highly Catalytically Active Noble Metal Nanoparticles on Reduced Graphene Oxide: A Non-Noble Metal Sacrificial Approach

In this work, we have developed a non-noble metal sacrificial approach for the first time to successfully immobilize highly dispersed AgPd nanoparticles on reduced graphene oxide (RGO). The Co₃(BO₃)₂ co-precipitated with AgPd nanoparticles and subsequently sacrificed by acid etching effectively prevents the primary AgPd particles from aggregation. The resulted ultrafine AgPd nanoparticles exhibit the highest activity (turnover frequency, 2739 h^–1 at 323 K) among all the heterogeneous catalysts for the dehydrogenation of formic acid to generate hydrogen without CO impurity. The sacrificial approach opens up a new avenue for the development of high-performance metal nanocatalysts

Fast Dehydrogenation of Formic Acid over Palladium Nanoparticles Immobilized in Nitrogen-Doped Hierarchically Porous Carbon

In this work, a hierarchically porous carbon was prepared from carbonization of a nitrogen-containing metal–organic framework, followed by activation under ultrasonication in aqueous potassium hydroxide (aq KOH). The activated carbon was applied as a support for immobilizing ultrafine palladium (Pd) nanoparticles (1.1 ± 0.2 nm). As a result, the as-prepared Pd nanoparticles on N-doped porous carbon with both micro- and mesoporosity exhibit an excellent activity for the dehydrogenation of formic acid, showing a high turnover frequency (TOF, 14 400 h–1) at 60 °C. This activation approach of carbon opens an avenue for the syntheses of highly active supported ultrafine metal NPs for catalysis

Metal–Organic Framework-Immobilized Polyhedral Metal Nanocrystals: Reduction at Solid–Gas Interface, Metal Segregation, Core–Shell Structure, and High Catalytic Activity

For the first time, this work presents surfactant-free monometallic and bimetallic polyhedral metal nanocrystals (MNCs) immobilized to a metal–organic framework (MIL-101) by CO-directed reduction of metal precursors at the solid–gas interface. With this novel method, Pt cubes and Pd tetrahedra were formed by CO preferential bindings on their (100) and (111) facets, respectively. PtPd bimetallic nanocrystals showed metal segregation, leading to Pd-rich core and Pt-rich shell. Core–shell Pt@Pd nanocrystals were immobilized to MIL-101 by seed-mediated two-step reduction, representing the first example of core–shell MNCs formed using only gas-phase reducing agents. These MOF-supported MNCs exhibited high catalytic activities for CO oxidation

Diamine-Alkalized Reduced Graphene Oxide: Immobilization of Sub‑2 nm Palladium Nanoparticles and Optimization of Catalytic Activity for Dehydrogenation of Formic Acid

An efficient strategy to downsize metal nanoparticles (NPs) and provide basic sites located nearby for optimizing the catalytic performance of reduced graphene oxide (rGO)-supported metal catalysts has been explored, for the first time, by potent alkalization of rGO with diamine. By virtue of the coordination effects between the metal ions and the amine groups ligated to rGO, monodispersed Pd nanoparticles (diameter ≤1.5 nm) can be facilely anchored on the diamine-alkalized rGO by a simple reduction approach. The turnover frequency (TOF) for heterogeneously catalyzed decomposition of formic acid reaches 3810 h^–1 at 323 K, the highest value ever reported under ambient conditions compared with the other heterogeneous catalysts

Molar-Fraction-Tunable Synthesis of Ag–Au Alloy Nanoparticles via a Dual Evaporation–Condensation Method as Supported Catalysts for CO Oxidation

The properties of nanoparticles composed of two metallic elements are affected by their synergy as well as the composition and structure of nanocrystals. Therefore, precise adjustment of the molar fractions of the constituent elements and crystal structure is required for their successful synthesis. An evaporation–condensation method, which represents an aerosol nanoparticle synthesis method, is based on the reagglomeration of metallic elements in the gas phase. In this study, we utilized a dual evaporation–condensation method with two furnaces to adjust the molar fractions of Ag–Au nanoparticles with an alloy-type nanocrystalline structure and obtain spherical particles with sizes smaller than 10 nm. The molar fraction of Ag atoms in the synthesized particles varied between 0 and 80% depending on the heating temperature. Energy-dispersive X-ray spectroscopy data revealed that Ag and Au elements were present in all particles and formed an alloy structure, suggesting that alloyed composite particles with different stoichiometries can be easily fabricated via the dual evaporation–condensation method. In addition, the nanoparticles generated in the gas phase were successfully recovered by immobilization on a substrate and served as effective bimetallic catalysts for CO oxidation. It is noteworthy that the preparation of nanoparticles and their fixation to a substrate in the proposed method were performed in one step

OCBBCO: A Neutral Molecule with Some Boron−Boron Triple Bond Character

Molecules that contain boron−boron multiple bonds are extremely rare due to the electron-deficient nature of boron. Here we report experimental and theoretical evidence of a neutral OCBBCO molecule with some boron−boron triple bond character. The molecule was produced and unambiguously characterized by matrix isolation infrared spectroscopy. Quantum chemical calculations indicate that the molecule has a linear singlet ground state with a very short boron−boron bond length

Interfacing with Fe–N–C Sites Boosts the Formic Acid Dehydrogenation of Palladium Nanoparticles

Hierarchical micro-/mesoporous carbons with abundant Fe–N–C sites were prepared through one-step carbonization of a metal–organic framework (MOF) with sodium iron ethylenediaminetetraacetic acid [NaFe­(III)­EDTA], which can facilitate the nucleation and growth of ultrafine (∼1.4 nm) and highly dispersed palladium nanoparticles (Pd NPs). Interfacing Pd NPs with Fe–N–C sites has been demonstrated for the first time to boost the heterogeneous catalysis of hydrogen production from formic acid, affording an ultrahigh turnover frequency (TOF) value of 7361 h–1 at 323 K. The robust synergistic interactions between Pd NPs and Fe–N–C sites together with the small size effects of Pd NPs are responsible for the enhanced catalytic activity