Fabrication of Gold and Silver Nanoparticles Supported on Zinc Imidazolate Metal-Organic Frameworks as Active Catalysts for Hydrogen Release from Ammonia Borane

Well-dispersed Au and Ag nanoparticles (NPs) have been immobilized on a zinc imidazolate metal-organic framework, Zn(mim), using the "one-pot" method and tested as catalysts in ammonia borane hydrolysis. The AuNPs@Zn(mim) and AgNPs@Zn(mim) materials were characterized by FTIR, XRD, ICP-OES, TGA, BET, SEM, and TEM. The AgNPs@Zn(mim) catalyst showed a high yield (98.5%) and high hydrogen generation rate (3352.71 mL min-1 gAg -1) in NH3BH3 dehydrogenation. The determined activation energies (19.6 kJ mol-1 for AuNPs@Zn(mim) and 38.13 kJ mol-1 for AgNPs@Zn(mim)) are lower than those for most reported catalysts containing Au/Ag-MOF used in the hydrolysis of NH3BH3. Moreover, the catalysts tested here revealed good stability and reusability, preserving 71.42% (AuNPs@Zn(mim)) and 88.23% (AgNPs@Zn(mim)) of their initial catalytic activities after five consecutive cycles. In the case of AgNPs@Zn(mim), the combination of the simple and green synthesis method, low active metal content, relatively low cost, and moderate dehydrogenation conditions makes the material an excellent candidate to produce hydrogen from ammonia borane.

Synergetic effect of Au nanoparticles and transition metal phosphides for enhanced hydrogen evolution from ammonia-borane

The hydrogen evolution from ammonia borane is intriguing but challenging due to its sluggish kinetics. In this regard, the gold nanoparticles amalgamation with metal phosphides is speculated to be more efficient catalysts. Here, the catalysts Au/Ni₂P and Au/CoP with the high synergetic effect of Au nanoparticles and metal phosphides were synthesized for ammonia borane hydrolysis. The activity of Au/Ni₂P increases 4.8-fold (i.e., 0.08 to 0.40 L∙h^-1) compared to pristine Ni₂P, and the activity of Au/CoP increases 1.7-fold (i.e., 0.74 to 1.27 L∙h^-1) compared to pristine CoP. This reveals that the synergetic effect of Au^δ+ and (Ni₂P) ^δ- is stronger than Au^δ+ and (CoP) ^δ- which is manifested by XPS analysis. The kinetics exposes that the activation energy of Au/Ni₂P (45.28 kJ∙mole^-1) is greater than Au/CoP (31.45 kJ∙mole^-1) and the TOF of Au/Ni₂P is less than Au/CoP. This research work presents an effective approach for producing active sites of Au^δ+ and (Ni₂P & CoP) ^δ- for ammonia borane hydrolysis to enhance the H₂ evolution rate.

Metal organic frameworks derived functional materials for energy and environment related sustainable applications

With the vigorous development of industrial economy, energy and environmental problems have become the most serious issues affecting people's production and life. Therefore, the demand for clean energy production, effective separation and storage is growing. Metal-organic frameworks (MOFs), as a kind of porous crystalline materials with large surface area and porosity, which is self-assembled by metal ions or clusters and organic ligands through coordination bonds. Thanks to a number of unique characteristics such as adjustable pore environment, homogeneous void structure, abundant active sites, unprecedented chemical composition tunability and functional versatility, it has been widely studied, especially for the clean energy conversion in catalysis. In this review, we focus on the research progress of clean energy in catalysis based on MOFs. Emphasis is placed on MOFs with different structures of compositions and their applications in catalytic for clean energy conversion, such as CO oxidation, CO₂ reduction and H₂ evolution. In addition, the situation of MOFs assisting environmental remediation is also briefly described. Finally, the prospects and challenges of MOFs in clean energy and the remaining issues in this field are presented.

Continuous spark plasma synthesis of Au/Co binary nanoparticles with tunable properties

We present here a scalable and environmentally friendly gas phase technique employing atmospheric pressure electrical spark discharge plasmas for the production of Au/Co binaries, an effective catalyst system for the decomposition of hydrogen-rich compounds, such as ammonium borane. We demonstrate that Au/Co alloy nanoparticles can be produced via the spark plasma-based technique. The possibility of varying the morphology and phase structure via real time heat treatment of the generated aerosol to form Au/Co/CoO particles with continuous control over a wide particle compositional range (from 24 to 64 at.% [Co]/([Co] + [Au]) content) is also demonstrated. Since our spark-based approach is proven to be capable of providing reasonable particle yields, these results may contribute to the transition of lab-scale, nanocatalyst-based hydrogen storage systems to real world applications.

Natural Wood-Based Catalytic Membrane Microreactors for Continuous Hydrogen Generation

The development of controlled processes for continuous hydrogen generation from solid-state storage chemicals such as ammonia borane is central to integrating renewable hydrogen into a clean energy mix. However, to date, most reported platforms operate in batch mode, posing a challenge for controllable hydrogen release, catalyst reusability, and large-scale operation. To address these issues, we developed flow-through wood-based catalytic microreactors, characterized by inherent natural oriented microchannels. The prepared structured catalysts utilize silver-promoted palladium nanoparticles supported on metal-organic framework (MOF)-coated wood microreactors as the active phase. Catalytic tests demonstrate their highly controllable hydrogen production in continuous mode, and by adjusting the ammonia borane flow and wood species, we reach stable productivities of up to 10.4 cm_H2³ min^-1 cm_cat^-3. The modular design of the structured catalysts proves readily scalable. Our versatile approach is applicable for other metals and MOF combinations, thus comprising a sustainable and scalable platform for catalytic dehydrogenations and applications in the energy-water nexus.

A new porphyrinic vanadium-based MOF constructed from infinite V(OH)O4 chains: syntheses, characterization and photoabsorption properties

A new porphyrinic vanadium-based metal–organic framework (MOF), namely V-MOF-10 [V2(OH)2(H2TCPP)], constructed from {V(OH)O4}∞ chains and 4-tetracarboxyphenylporphyrin linkers, was synthesized by a solvothermal procedure.

Advances and Prospects in Metal-Organic Frameworks as Key Nexus for Chemocatalytic Hydrogen Production

Hydrogen is a clean and sustainable energy carrier, which is considered a promising alternative for fossil fuels to solve the global energy crisis and respond to climate change. Social concerns on its safe storage promote continuous exploration of alternatives to traditional storage methods. In this case, chemical hydrogen storage materials initiate plentiful research with special attention to the design of heterogeneous catalysts that can enhance efficient and highly selective hydrogen production. Metal-organic frameworks (MOFs), a kind of unique crystalline porous materials featuring highly ordered porosities and tailorable structures, can provide various active sites (i.e., metal nodes, functional linkers, and defects) for heterogeneous catalysis. Furthermore, the easy construction of active sites in highly ordered MOFs, which can work as plate for the delicate active site engineering, make them ideal candidates for a variety of heterogeneous catalysts including chemocatalytic hydrogen production. This review concentrates on the application of MOFs as heterogeneous catalysts or catalyst supports in chemocatalytic hydrogen production. Recent progresses of MOFs as catalysts for chemocatalytic hydrogen production are comprehensively summarized. The research methods, mechanism analyses, and prospects of MOFs in this field are discussed. The challenges in future industrial applications of MOFs as catalysts for hydrogen production are proposed.

Sensitive fluorescence and visual detection of organophosphorus pesticides with a Ru(bpy)32+-ZIF-90-MnO2 sensing platform

Fluorescence sensing organophosphorus pesticides (OPs) is of great importance for both food safety and global environment; however, the reported fluorescent probes are usually directly exposed to the external environment, resulting in premature leakage or photobleaching and thus limiting their photostability and assay sensitivity. In this work, a fluorescent sensing platform consisting of a novel luminescent metal-organic framework (Ru(bpy)₃²⁺-ZIF-90) and manganese dioxide nanosheets (MnO₂ NSs) was prepared for sensing OPs. Due to the protection and improvement in the fluorescence of Ru(bpy)₃²⁺ by ZIF-90, the Ru(bpy)₃²⁺-ZIF-90 probe displayed remarkable photostability and high stability in water. By virtue of the high stability of Ru(bpy)₃²⁺-ZIF-90, as well as the outstanding fluorescence quenching and notable recognition ability of the MnO₂ NSs, this sensing platform provided excellent detection capability for parathion-methyl, with a wide concentration range of 0.050-60 ng mL^-1 and a low detection limit of 0.037 ng mL^-1. Additionally, the system exhibited a visual color change with the concentration of the OPs under sunlight. Moreover, satisfactory recoveries ranging from 93.3% to 103.6% were obtained for the real samples. The results indicated that the Ru(bpy)₃²⁺-ZIF-90-MnO₂-based OP sensing platform is promising for applications in food safety and environmental monitoring.

Synthesis of stable and highly efficient Au@ZIF-8 for selective hydrogenation of nitrophenol

A series of nanoparticles (NPs) with different Au content was successfully encapsulated into metal organic framework ZIF-8 with highly porous structure through room-temperature crystallization. X-ray diffraction, Fourier transform infrared spectroscopy, N₂ adsorption and transmission electron microscopy were carried out to characterize the obtained Au@ZIF-8 heterogeneous catalytic material comprehensively. Au NPs were dispersed uniformly in the ZIF-8 and the Au NP diameter was 5-6 nm. The crystal structure of ZIF-8 was unchanged when compared with that before Au loading. It was found that the Au content plays an important role in the hydrogenation reaction. The obtained Au@ZIF-8 exhibited high hydrogenation activity to nitrophenol and excellent selectivity to aminophenol. The recyclability of the Au@ZIF-8 catalysts showed excellent catalytic performance and great stability in the recycling reaction.

One-dimensional hollow FePt nanochains: applications in hydrolysis of NaBH4 and structural stability under Ga+ ion irradiation

Pt-based one-dimensional hollow nanostructures are promising catalysts in fuel cells with excellent activity. Herein, one-dimensional hollow FePt nanochains were shown to be efficient nanocatalysts in the hydrolysis of NaBH₄. The characterization of composition, structure and morphology identifies an ultrathin shell (∼3 nm) with uniformly distributed Fe₃₀Pt₇₀ constituents. The H₂ generation rate of hollow Fe₃₀Pt₇₀ nanochains achieves 16.9 l/(min · g) at room temperature, while the activation energy is as low as 17.6 kJ mol^-1 based on the fitting over the whole reaction time span. After the catalysis of NaBH₄ hydrolysis, the morphology and composition of hollow FePt nanochains remain unchanged. Furthermore, the structural stability of hollow FePt nanochains under Ga⁺ ion irradiation is clarified. Theoretical simulation indicates that the stopping range of such a Fe₃₀Pt₇₀ shell is 7.7 keV, which offers a prediction that structure evolves diversely under Ga⁺ ions below and above such energy. The Ga⁺ ion irradiation experiments show a consistent trend with the simulation, where Ga⁺ ions with kinetic energy of 30 keV make the hollow architecture subside and sputter away, while Ga⁺ ions with kinetic energy of 5 keV only etch the top and lead to an eggshell structure.

In situ synthesized hollow spheres of a silica–ruthenium–nickel composite catalyst for the hydrolytic dehydrogenation of ammonia borane

The present study investigated the fabrication of hollow spheres of a silica–ruthenium–nickel composite catalyst for the hydrolitic dehydrogenation of ammonia borane.

MIL/Aptamer as a Nanosensor Capable of Resisting Nonspecific Displacement for ATP Imaging in Living Cells

Fluorescent probes physisorbed on nanomaterials have emerged as a kind of useful and facile sensing platform for biological important molecules. However, nonspecific displacement in the physisorption systems is a non-negligible problem for the intracellular analysis. MIL (Materials of Institut Lavoisier), a subclass of metal-organic frameworks (MOFs), has high porosity, large surface area, and intriguing three-dimensional (3D) nanostructure with promising biological and biomedical applications such as molecular detection and drug delivery. Herein, we report MIL/aptamer-FAM as a nanosensor capable of resisting nonspecific displacement for intracellular adenosinetriphosphate (ATP) sensing and imaging. In this approach, by virtue of the remarkable quenching capability, high affinity of aptamers, and dramatic capability of resisting nonspecific displacement of 3D MIL-100, the assay and imaging of ATP in living cells were realized. Our results demonstrated that the MIL/aptamer-FAM nanosensor not only shows high selectivity for the detection of ATP in buffer but also is able to act as a "signal-on" nanosensor for specific imaging of ATP in living cells. The strategy reported here opens up a new way to develop MOF-based nanosensors for intracellular delivery and metabolite detection.

Metal-Organic Frameworks Encapsulating Active Nanoparticles as Emerging Composites for Catalysis: Recent Progress and Perspectives

Beyond conventional porous materials, metal-organic frameworks (MOFs) have aroused great interest in the construction of nanocatalysts with the characteristics of catalytically active nanoparticles (NPs) confined into the cavities/channels of MOFs or surrounded by MOFs. The advantages of adopting MOFs as the encapsulating matrix are multifold: uniform and long-range ordered cavities can effectively promote the mass transfer and diffusion of substrates and products, while the diverse metal nodes and tunable organic linkers may enable outstanding synergy functions with the encapsulated active NPs. Herein, some key issues related to MOFs for catalysis are discussed. Then, state-of-the art progress in the encapsulation of catalytically active NPs by MOFs as well as their synergy functions for enhanced catalytic performance in the fields of thermo-, photo-, and electrocatalysis are summarized. Notably, encapsulation-structured nanocatalysts exhibit distinct advantages over conventional supported catalysts, especially in terms of the catalytic selectivity and stability. Finally, challenges and future developments in MOF-based encapsulation-structured nanocatalysts are proposed. The aim is to deliver better insight into the design of well-defined nanocatalysts with atomically accurate structures and high performance in challenging reactions.

Dynamic Motion of Organic Ligands in Polar Layered Cobalt Phosphonates

By introducing the polar methoxy group into phenyl- or benzyl-phosphonate ligands, four cobalt phosphonates with layered structures are obtained, namely, [Co(4-mopp)(H₂ O)] (1), [Co(4-mobp)(H₂ O)] (2), [Co(3-mopp)(H₂ O)] (3), and [Co(3-mobp)(H₂ O)] (4), where 4- or 3-moppH₂ is (4- or 3-methoxyphenyl)phosphonic acid and 4- or 3-mobpH₂ is (4- or 3-methoxybenzyl)phosphonic acid. Compounds 1, 2, and 4 crystallize in the polar space groups Pmn2₁ or Pna2₁ , whereas compound 3 crystallizes in the centrosymmetric space group P2₁ /n. The layer topologies in the four structures are similar and can be viewed as perovskite type, where the edge-sharing [Co₄ O₄ ] rhombi are capped by the PO₃ C groups. The phenyl and MeO groups in compounds 1-3 are heavily disordered, whereas that in 4 is ordered. Structural comparison based on the data at 296 and 123 K reveals distinct dynamic motion of the organic groups in compounds 1 and 2. The fluctuation of the polar MeO groups in these two compounds is confirmed by dielectric relaxation measurements. In contrast, the fluctuation of polar groups in compounds 3 and 4 is not evident. Interestingly, the dehydrated samples of 3 and 4 (i.e., 3-de and 4-de) exhibit one-step and two-step phase transitions associated with the motion of polar organic groups, as proven by DSC and dielectric measurements. The magnetic properties of compounds 1-4 are investigated, and strong antiferromagnetic interactions are found to mediate between the magnetic centers through μ-O(P) and O-P-O bridges.

The development of MOFs-based nanomaterials in heterogeneous organocatalysis

Metal-organic framework (MOF) is a class of inorganic-organic hybrid material assembled periodically with metal ions and organic ligands. MOFs have always been the focuses in a variety of frontier fields owing to the advantageous properties, such as large BET surface areas, tunable porosity and easy-functionalized surface structure. Among the various application areas, catalysis is one of the earliest application fields of MOFs-based materials and is one of the fastest-growing topics. In this review, the main roles of MOFs in heterogeneous organocatalysis have been systematically summarized, including used as support materials (or hosts), independent catalysts, and sacrificial templates. Moreover, the application prospects of MOFs in photocatalysis and electrocatalysis frontiers were also mentioned. Finally, the key issues that should be conquered in future were briefly sketched in the final parts of each item. We hope our perspectives could be beneficial for the readers to better understand these topics and issues, and could also provide a direction for the future exploration of some novel types of MOFs-based nanocatalysts with stable structures and functions for heterogeneous catalysis.

In Situ Formation of AgCo Stabilized on Graphitic Carbon Nitride and Concomitant Hydrolysis of Ammonia Borane to Hydrogen

The development of highly-efficient heterogeneous supported catalysts for catalytic hydrolysis of ammonia borane to yield hydrogen is of significant importance considering the versatile usages of hydrogen. Herein, we reported the in situ synthesis of AgCo bimetallic nanoparticles supported on g-C₃N₄ and concomitant hydrolysis of ammonia borane for hydrogen evolution at room temperature. The as-synthesized Ag0.1Co0.9/g-C₃N₄ catalysts displayed the highest turnover frequency (TOF) value of 249.02 mol H₂·(molAg·min)−1 for hydrogen evolution from the hydrolysis of ammonia borane, which was higher than many other reported values. Furthermore, the Ag0.1Co0.9/g-C₃N₄ catalyst could be recycled during five consecutive runs. The study proves that Ag0.1Co0.9/g-C₃N₄ is a potential catalytic material toward the hydrolysis of ammonia borane for hydrogen production.

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.

Au–Fe nanoparticles visited by MD simulation: structural and thermodynamic properties affected by chemical composition

In this work, Fe–Au nanoalloys and Fe@Au core–shell nanoclusters are investigated via classical molecular dynamics simulation to determine the effect of their composition on their thermodynamic stability and melting mechanism.

Nanoparticle/Metal-Organic Framework Composites for Catalytic Applications: Current Status and Perspective

Nanoparticle/metal-organic frameworks (MOF) based composites have recently attracted significant attention as a new class of catalysts. Such composites possess the unique features of MOFs (including clearly defined crystal structure, high surface area, single site catalyst, special confined nanopore, tunable, and uniform pore structure), but avoid some intrinsic weaknesses (like limited electrical conductivity and lack in the "conventional" catalytically active sites). This review summarizes the developed strategies for the fabrication of nanoparticle/MOF composites for catalyst uses, including the strategy using MOFs as host materials to hold and stabilize the guest nanoparticles, the strategy with subsequent MOF growth/assembly around pre-synthesized nanoparticles and the strategy mixing the precursors of NPs and MOFs together, followed by self-assembly process or post-treatment or post-modification. The applications of nanoparticle/MOF composites for CO oxidation, CO₂ conversion, hydrogen production, organic transformations, and degradation of pollutants have been discussed. Superior catalytic performances in these reactions have been demonstrated. Challenges and future developments are finally addressed.

Synthesis and Electrochemical Performance of SnOx Quantum Dots@ UiO-66 Hybrid for Lithium Ion Battery Applications

A novel method that combines the dehydration of inorganic clusters in metal-organic frameworks (MOFs) with nonaqueous sol-gel chemistry and pyrolysis processes is developed to synthesize SnO_x quantum dots@Zr-MOFs (UIO-66) composites. The size of as-prepared SnO_x nanoparticles is approximately 4 nm. Moreover, SnO_x nanoparticles are uniformly anchored on the surface of the Zr-MOFs, which serves as a matrix to alleviate the agglomeration of SnO_x grains. This structure provides an accessible surrounding space to accommodate the volume change of SnO_x during the charge/discharge process. Cyclic voltammetry and galvanostatic charge/discharge were employed to examine the electrochemical properties of the ultrafine SnO_x@Zr-MOF (UIO-66) material. Benefiting from the advantages of the smaller size of SnO_x nanoparticles and the synergistic effect between SnO_x nanoparticles and the Zr-MOFs, the SnO_x@Zr-MOF composite exhibits enhanced electrochemical performance when compared to that of its SnO_x bulk counterpart. Specifically, the discharge-specific capacity of the SnO_x@Zr-MOF electrode can still remain at 994 mA h g^-1 at 50 mA g^-1 after 100 cycles. The columbic efficiencies can reach 99%.

Highly Efficient Catalytic Hydrogen Evolution from Ammonia Borane Using the Synergistic Effect of Crystallinity and Size of Noble-Metal-Free Nanoparticles Supported by Porous Metal-Organic Frameworks

A series of nonprecious metal nanoparticles (NPs) supported by metal-organic framework MIL-101 were synthesized using four methods and their catalytic performance on hydrogen evolution from ammonia borane (NH₃BH₃) was studied. The results showed that the crystalline Co NPs with size of 4.5-8.5 and 14.5-24.5 nm had low activities featuring the total turnover frequency (TOF) values of 9.9 and 4.5 mol_H2 mol_cat^-1 min^-1, respectively. In contrast, the amorphous Co NPs with size of 1.6-2.6 and 13.5-24.5 nm exhibited high activities featuring the total TOF values of 51.4 and 22.3 mol_H2 mol_cat^-1 min^-1, respectively. The remarkably different activities could be ascribed to the different crystallinity and size of Co NPs in the catalysts. Moreover, the ultrasound-assisted in situ method was also successfully applied to bimetallic systems, and MIL-101-supported amorphous CuCo, FeCo and NiCo NPs had the catalytic activities with total TOF values of 51.7, 50.8, and 44.3 mol_H2 mol_cat^-1 min^-1, respectively, which were the highest in the values of the reported non-noble metal Co-based catalysts. The present approach, namely, using the synergistic effect of crystallinity and size of metal NPs, may offer a new prospect for high-performance and low-cost nanocatalysts.

AuFePt Ternary Homogeneous Alloy Nanoparticles with Magnetic and Plasmonic Properties

Combining Au and Fe into a single nanoparticle is an attractive way to engineer a system possessing both plasmonic and magnetic properties simultaneously. However, the formation of the AuFe alloy is challenging because of the wide miscibility gap for these elements. In this study, we synthesized AuFePt ternary alloy nanoparticles as an alternative to AuFe alloy nanoparticles, where Pt is used as a mediator that facilitates alloying between Au and Fe in order to form ternary alloy nanoparticles. The relationship among composition, structure, and function is investigated and it was found that at an optimized composition (Au₅₂Fe₃₀Pt₁₈), ternary alloy NPs exhibit both magnetic and plasmonic properties simultaneously. The plasmonic properties are investigated in detail using a theoretical Mie model, and we found that it is governed by the dielectric constant of the resulting materials.

Efficient Pd@MIL-101(Cr) hetero-catalysts for 2-butyne-1,4-diol hydrogenation exhibiting high selectivity

An efficient Pd@MIL-101(Cr) catalyst prepared with MOCVD approach for 2-butyne-1,4-diol hydrogenation with excellent activity, stability and selectivity.

Multifunctional metal–organic framework catalysts: synergistic catalysis and tandem reactions

Various active sites incorporated into metal–organic frameworks (MOFs) are suitable for synergistic catalysis and tandem reactions.

Hydrothermal Synthesis and Catalytic Application of Ultrathin Rhodium Nanosheet Nanoassemblies

Ultrathin noble metal nanosheets with atomic thickness exhibit abnormal electronic, surfacial, and photonic properties due to the unique two-dimensional (2D) confinement effect, which have attracted intensive research attention in catalysis/electrocatalysis. In this work, the well-defined ultrathin Rh nanosheet nanoassemblies with dendritic morphology are synthesized by a facile hydrothermal method with assistance of poly(allylamine hydrochloride) (PAH), where PAH effectively acts as the complexant and shape-directing agent. Transmission electron microscopy and atomic force microscopy images reveal the thickness of 2D Rh nanosheet with (111) planes is only ca. 0.8-1.1 nm. Nitrogen adsorption-desorption measurement displays the specific surface area of the as-prepared ultrathin Rh nanosheet nanoassemblies is 139.4 m² g^-1, which is much bigger than that of homemade Rh black (19.8 m² g^-1). Detailed catalytic investigations display the as-prepared ultrathin Rh nanosheet nanoassemblies have nearly 20.4-fold enhancement in mass-activity for the hydrolysis of ammonia borane as compared with homemade Rh black.

Covalent triazine framework supported non-noble metal nanoparticles with superior activity for catalytic hydrolysis of ammonia borane: from mechanistic study to catalyst design

Development of non-noble metal catalysts with similar activity and stability to noble metals is of significant importance in the conversion and utilization of clean energies.

Development of non-noble metal catalysts with similar activity and stability to noble metals is of significant importance in the conversion and utilization of clean energy. The catalytic hydrolysis of ammonia borane (AB) to produce 3 equiv. of H₂, as an example of where noble metal catalysts significantly outperform their non-noble peers, serves as an excellent test site for the design and optimization of non-noble metal catalysts. Our kinetic isotopic effect measurements reveal, for the first time, that the kinetic key step of the hydrolysis is the activation of H₂O. Deducibly, a transition metal with an optimal electronic structure that bonds H₂O and –OH in intermediate strengths would favor the hydrolysis of AB. By employing a covalent triazine framework (CTF), a newly developed porous material capable of donating electrons through the lone pairs on N, the electron densities of nano-sized Co and Ni supported on CTF are markedly increased, as well as their catalytic activities. Specifically, Co/CTF exhibits a total turnover frequency of 42.3 mol_H2 mol_Co^–1 min^–1 at room temperature, which is superior to all peer non-noble metal catalysts ever reported and even comparable to some noble metal catalysts.

Non-Noble-Metal Nanoparticle Supported on Metal-Organic Framework as an Efficient and Durable Catalyst for Promoting H2 Production from Ammonia Borane under Visible Light Irradiation

In this work, we propose a straightforward method to enhance the catalytic activity of AB dehydrogenation by using non-noble-metal nanoparticle supported on chromium-based metal-organic framework (MIL-101). It was demonstrated to be effective for hydrogen generation from ammonia borane under assistance of visible light irradiation as a noble-metal-free catalyst. The catalytic activity of metal nanoparticles supported on MIL-101 under visible light irradiation is remarkably higher than that without light irradiation. The TOFs of Cu/MIL-101, Co/MIL-101, and Ni/MIL-101 are 1693, 1571, and 3238 h(-1), respectively. The enhanced activity of catalysts can be primarily attributed to the cooperative promoting effects from both non-noble-metal nanoparticles and photoactive metal-organic framework in activating the ammonia borane molecule and strong ability in the photocatalytic production of hydroxyl radicals, superoxide anions, and electron-rich non-noble-metal nanoparticle. This work sheds light on the exploration of active non-noble metals supported on photoactive porous materials for achieving high catalytic activity of various redox reactions under visible light irradiation.

Porous Materials for Hydrolytic Dehydrogenation of Ammonia Borane

Hydrogen storage is still one of the most significant issues hindering the development of a “hydrogen energy economy”. Ammonia borane is notable for its high hydrogen densities. For the material, one of the main challenges is to release efficiently the maximum amount of the stored hydrogen. Hydrolysis reaction is a promising process by which hydrogen can be easily generated from this compound. High purity hydrogen from this compound can be evolved in the presence of solid acid or metal based catalyst. The reaction performance depends on the morphology and/or structure of these materials. In this review, we survey the research on nanostructured materials, especially porous materials for hydrogen generation from hydrolysis of ammonia borane.