Hydrogen has emerged as an environmentally attractive fuel and a promising energy carrier for future applications to meet the ever‐increasing energy challenges. The safe and efficient storage and ...release of hydrogen remain a bottleneck for realizing the upcoming hydrogen economy. Hydrogen storage based on liquid‐phase chemical hydrogen storage materials is one of the most promising hydrogen storage techniques, which offers considerable potential for large‐scale practical applications for its excellent safety, great convenience, and high efficiency. Recently, nanopore‐supported metal nanocatalysts have stood out remarkably in boosting the field of liquid‐phase chemical hydrogen storage. Herein, the latest research progress in catalytic hydrogen production is summarized, from liquid‐phase chemical hydrogen storage materials, such as formic acid, ammonia borane, hydrous hydrazine, and sodium borohydride, by using metal nanocatalysts confined within diverse nanoporous materials, such as metal–organic frameworks, porous carbons, zeolites, mesoporous silica, and porous organic polymers. The state‐of‐the‐art synthetic strategies and advanced characterizations for these nanocatalysts, as well as their catalytic performances in hydrogen generation, are presented. The limitation of each hydrogen storage system and future challenges and opportunities on this subject are also discussed. References in related fields are provided, and more developments and applications to achieve hydrogen energy will be inspired.
Recent research progress on nanopore‐supported metal nanocatalysts for H2 generation from various liquid‐phase chemical hydrogen storage materials is reviewed, mainly focusing on the presentation of state‐of‐the‐art synthetic strategies and advanced characterizations of these nanocatalysts and their catalytic performances in hydrogen generation. Some drawbacks of each hydrogen storage system and challenges and opportunities in future research are also highlighted.
Crystalline nanoporous materials with uniform porous structures, such as zeolites and metal–organic frameworks (MOFs), have proven to be ideal supports to encapsulate ultrasmall metal nanoparticles ...(MNPs) inside their void nanospaces to generate high‐efficiency nanocatalysts. The nanopore‐encaged metal catalysts exhibit superior catalytic performance as well as high stability and catalytic shape selectivity endowed by the nanoporous matrix. In addition, the synergistic effect of confined MNPs and nanoporous frameworks with active sites can further promote the catalytic activities of the composite catalysts. Herein, recent progress in nanopore‐encaged metal nanocatalysts is reviewed, with a special focus on advances in synthetic strategies for ultrasmall MNPs (<5 nm), clusters, and even single atoms confined within zeolites and MOFs for various heterogeneous catalytic reactions. In addition, some advanced characterization methods to elucidate the atomic‐scale structures of the nanocatalysts are presented, and the current limitations of and future opportunities for these fantastic nanocatalysts are also highlighted and discussed. The aim is to provide some guidance for the rational synthesis of nanopore‐encaged metal catalysts and to inspire their further applications to meet the emerging demands in catalytic fields.
Recent advancements in nanopore‐encaged metal nanocatalysts are reviewed, mainly focusing on presenting the state‐of‐the‐art strategies for the fabrication of ultrasmall metal nanoparticles (<5 nm), clusters, and even single atoms confined within crystalline nanoporous materials including zeolites and metal–organic frameworks. Some related catalytic applications and advanced characterization methods are introduced, and the current limitations of and future opportunities for these fantastic nanocatalysts are also highlighted.
Well-dispersed and ultrasmall Pd clusters in nanosized silicalite-1 (MFI) zeolite have been prepared under direct hydrothermal conditions using Pd(NH2CH2CH2NH2)2Cl2 as precursor. High-resolution ...scanning transmission electron microscopy studies indicate that the Pd clusters are encapsulated within the intersectional channels of MFI, and the Pd clusters in adjacent channels visually aggregate, forming nanoparticles (NPs) of ∼1.8 nm. The resultant catalysts show an excellent activity and highly efficient H2 generation toward the complete decomposition of formic acid (FA) under mild conditions. Notably, thanks to the further reduced Pd NP size (∼1.5 nm) and the additionally introduced basic sites, the Pd/S-1-in-K catalyst affords turnover frequency values up to 856 h–1 at 25 °C and 3027 h–1 at 50 °C. The easy in situ confinement synthesis of metal clusters in zeolites endows the catalysts with superior catalytic activities, excellent recyclability, and high thermal stability, thus opening new perspectives for the practical application of FA as a viable and effective H2 storage material for use in fuel cells.
Single‐atom catalysts are emerging as a new frontier in heterogeneous catalysis because of their maximum atom utilization efficiency, but they usually suffer from inferior stability. Herein, we ...synthesized single‐atom Rh catalysts embedded in MFI‐type zeolites under hydrothermal conditions and subsequent ligand‐protected direct H2 reduction. Cs‐corrected scanning transmission electron microscopy and extended X‐ray absorption analyses revealed that single Rh atoms were encapsulated within 5‐membered rings and stabilized by zeolite framework oxygen atoms. The resultant catalysts exhibited excellent H2 generation rates from ammonia borane (AB) hydrolysis, up to 699 min−1 at 298 K, representing the top level among heterogeneous catalysts for AB hydrolysis. The catalysts also showed superior catalytic performance in shape‐selective tandem hydrogenation of various nitroarenes by coupling with AB hydrolysis, giving >99 % yield of corresponding amine products.
Together alone: Single Rh atoms were encapsulated within MFI zeolites under in situ hydrothermal conditions and a ligand‐protected direct H2 reduction. The catalyst gave a high turnover frequency of 699 molH2
(molRh)−1 min−1 at 298 K for ammonia borane (AB) hydrolysis and exhibited superior catalytic efficiency in shape‐selective tandem hydrogenation of nitroarenes by coupling with the hydrolysis of AB.
We present the results of Gaussian-based ground-state and excited-state equation-of-motion coupled-cluster theory with single and double excitations for three-dimensional solids. We focus on diamond ...and silicon, which are paradigmatic covalent semiconductors. In addition to ground-state properties (the lattice constant, bulk modulus, and cohesive energy), we compute the quasiparticle band structure and band gap. We sample the Brillouin zone with up to 64 k-points using norm-conserving pseudopotentials and polarized double- and triple-ζ basis sets, leading to canonical coupled-cluster calculations with as many as 256 electrons in 2176 orbitals.
We introduce the atomic valence active space (AVAS), a simple and well-defined automated technique for constructing active orbital spaces for use in multiconfiguration and multireference (MR) ...electronic structure calculations. Concretely, the technique constructs active molecular orbitals capable of describing all relevant electronic configurations emerging from a targeted set of atomic valence orbitals (e.g., the metal d orbitals in a coordination complex). This is achieved via a linear transformation of the occupied and unoccupied orbital spaces from an easily obtainable single-reference wave function (such as from a Hartree–Fock or Kohn–Sham calculations) based on projectors to targeted atomic valence orbitals. We discuss the premises, theory, and implementation of the idea, and several of its variations are tested. To investigate the performance and accuracy, we calculate the excitation energies for various transition-metal complexes in typical application scenarios. Additionally, we follow the homolytic bond breaking process of a Fenton reaction along its reaction coordinate. While the described AVAS technique is not a universal solution to the active space problem, its premises are fulfilled in many application scenarios of transition-metal chemistry and bond dissociation processes. In these cases the technique makes MR calculations easier to execute, easier to reproduce by any user, and simplifies the determination of the appropriate size of the active space required for accurate results.
A facile and cost-effective strategy has been developed to synthesize nano-sized SAPO-34 zeolite catalysts with intracrystalline meso-macroporosity as well as high crystallinity and product yield via ...the seed-assisted method using triethylamine as the sole template. Significantly, compared to conventional micron-sized microporous SAPO-34 zeolites, the nano-sized hierarchical SAPO-34 zeolites show superior performance in the methanol-to-olefin (MTO) reaction with a 4-fold prolonged catalytic lifetime and remarkably improved selectivity for ethylene and propylene reaching up to 85.0%, which is among the highest catalytic performances in the MTO reaction ever reported under similar conditions.
A CO2‐mediated hydrogen storage energy cycle is a promising way to implement a hydrogen economy, but the exploration of efficient catalysts to achieve this process remains challenging. Herein, ...sub‐nanometer Pd–Mn clusters were encaged within silicalite‐1 (S‐1) zeolites by a ligand‐protected method under direct hydrothermal conditions. The obtained zeolite‐encaged metallic nanocatalysts exhibited extraordinary catalytic activity and durability in both CO2 hydrogenation into formate and formic acid (FA) dehydrogenation back to CO2 and hydrogen. Thanks to the formation of ultrasmall metal clusters and the synergic effect of bimetallic components, the PdMn0.6@S‐1 catalyst afforded a formate generation rate of 2151 molformate molPd−1 h−1 at 353 K, and an initial turnover frequency of 6860 molH2
molPd−1 h−1 for CO‐free FA decomposition at 333 K without any additive. Both values represent the top levels among state‐of‐the‐art heterogeneous catalysts under similar conditions. This work demonstrates that zeolite‐encaged metallic catalysts hold great promise to realize CO2‐mediated hydrogen energy cycles in the future that feature fast charge and release kinetics.
Sub‐nanometer Pd–Mn clusters were encaged within silicalite‐1 zeolites by a ligand‐protected method under direct hydrothermal conditions. The obtained zeolite‐encaged metallic nanocatalysts exhibited a record formate generation rate of 2151 molformate molPd−1 h−1 at 353 K, and an excellent initial turnover frequency of 6860 molH2
molPd−1 h−1 for CO‐free formic acid decomposition at 333 K without any additive.
Propane dehydrogenation (PDH) has great potential to meet the increasing global demand for propylene, but the widely used Pt‐based catalysts usually suffer from short‐term stability and ...unsatisfactory propylene selectivity. Herein, we develop a ligand‐protected direct hydrogen reduction method for encapsulating subnanometer bimetallic Pt–Zn clusters inside silicalite‐1 (S‐1) zeolite. The introduction of Zn species significantly improved the stability of the Pt clusters and gave a superhigh propylene selectivity of 99.3 % with a weight hourly space velocity (WHSV) of 3.6–54 h−1 and specific activity of propylene formation of 65.5 molC3H6
gPt−1 h−1 (WHSV=108 h−1) at 550 °C. Moreover, no obvious deactivation was observed over PtZn4@S‐1‐H catalyst even after 13000 min on stream (WHSV=3.6 h−1), affording an extremely low deactivation constant of 0.001 h−1, which is 200 times lower than that of the PtZn4/Al2O3 counterpart under the same conditions. We also show that the introduction of Cs+ ions into the zeolite can improve the regeneration stability of catalysts, and the catalytic activity kept unchanged after four continuous cycles.
A lean, mean, propylene machine: Subnanometer bimetallic Pt–Zn clusters are encapsulated inside silicalite‐1 (S‐1) zeolite via a ligand‐protected direct hydrogen reduction method. In the propane dehydrogenation (PDH) reaction, the PtZn4@S‐1‐H catalyst exhibited a very high propylene selectivity of 99.3 % and specific activity of propylene formation of 65.5 molC3H6
gPt−1 h−1 at 550 °C. Moreover, no obvious deactivation was observed over catalyst even after 13000 min on stream.
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