In Situ Neutron Powder Diffraction and X-ray Photoelectron Spectroscopy Analyses on the Hydrogenation of MOF-5 by Pt-Doped Multiwalled Carbon Nanotubes

Abstract

Recent research on hydrogen storage in metal–organic frameworks focuses on how to achieve increased hydrogen binding energies by using doped metal, using unsaturated metal ions, or forming composites comprising Pt-doped carbon materials. In particular, noticeable progress using MOFs and Pt-doped carbons has been achieved to enhance the hydrogen storage capacity near room temperature. A three-component composite material, Pt-MWCNT-MOF5 (PMM5), which is a metal–organic framework (MOF-5) hybridized with Pt nanoparticles on multiwalled carbon nanotubes (MWCNT), stores 0.22 wt % hydrogen at 320 K and 30 bar, which is larger than 0.13 wt % at 300 K and 30 bar. Although the increased quantity is small, it is possible to detect the origin of uptake increase based on various analyses. In situ neutron diffraction experiments of deuterium-sorbed PMM5 with a temperature cycling process (D2 loading at 50 K → 4 K → 320 K, 2 h → 50 K → 4 K) result in a significant background increase owing to both chemisorbed deuterium atoms and a local deformation of the MOF-5 framework. Hydrogen loading in PMM5 induces significant binding energy shifts in C 1s and Zn 2p3/2 electrons in the X-ray photoelectron spectra, suggesting the chemical environment change in Zn4O(COO)6 coordination sphere in MOF-5. All accumulated experimental data support the fact that the hydrogen receptor is the oxygen atoms of benzene-1,4-dicarboxylates of MOF-5, which is facilitated by the embedded Pt-MWCNT.

Review on processing of metal-organic framework (MOF) materials towards system integration for hydrogen storage

“…Because hydrogen uptake in MOF materials can be influenced by the pore characteristics and mesopores (2–50 nm) in certain MOFs are often reported to be too large to adsorb hydrogen effectively, composites can be fabricated to achieve higher hydrogen storage capacity by adjustment of pore sizes . In fact, the incorporation of either two MOF materials or MOF with other components, to optimize the pore geometry and surface structure, has shown promise to achieve higher hydrogen uptake . The hybrid composites conserve the characteristic individual features of both materials and also show synergetic hybrid properties derived from the different components.…”

Hybrid metal-organic framework nanomaterials with enhanced carbon dioxide and methane adsorption enthalpy by incorporation of carbon nanotubes

“…With the advantages of the porosity, the large surface areas and the uniform pore characteristics, these MOF materials have great potential for a variety of applications, such as gas storage, chemical separation, catalysis, sensing and drug delivery [19][20][21][22]. Furthermore, owing to the diversity of metal centres and functional ligands, MOF materials offer the opportunity of developing new types of composite materials that may show enhanced gas storage properties or new behaviour compared with the original MOFs [15,[23][24][25][26][27][28][29][30][31].…”

“…With the advantages of the porosity, the large surface areas and the uniform pore characteristics, these MOF materials have great potential for a variety of applications, such as gas storage, chemical separation, catalysis, sensing and drug delivery [19][20][21][22]. Furthermore, owing to the diversity of metal centres and functional ligands, MOF materials offer the opportunity of developing new types of composite materials that may show enhanced gas storage properties or new behaviour compared with the original MOFs [15,[23][24][25][26][27][28][29][30][31].In our previous work, we synthesised a kind of MOF material, Dy(BTC)(H 2 O)·DMF (named JUC-32, JUC = Jilin University, China)[32], which exhibits excellent thermal stability and high carbon dioxide storage capability. We then successfully used JUC-32-Y (replacing the metal Dy with Y) as the host for a hybrid material, by assembling guest molecules of ammonia borane (AB) materials, which exhibited a dramatic improvement in the hydrogen release kinetics, the lower operational temperature and the purity of the released hydrogen [33].…”

Formation of Frustrated Lewis Pairs in Ptx‐Loaded Zeolite NaY

“…Since the hydrogen nucleus ( 1 H) has av ery large neutron incoherent scattering (NIS) cross-section (80.26 barns) even avery small amount of hydrogen within the sample can cause asignificant increase in the background signal. [16] Figure 1A shows the simultaneous rise of the Bragg peak intensity and the background level after admission of H 2 and heat treatment. Table S2) nicely coincide with the probability distribution of positive (blue clouds) and negative (red clouds) neutron scattering length densities deduced from amaximum entropy method (MEM) analysis.…”