101. Effect of metal catalyst on the mechanism of hydrogen spillover in three-dimensional covalent-organic frameworks.
- Author
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Xiu-Ying Liu, Jing-Xin Yu, Xiao-Dong Li, Gui-Cheng Liu, Xiao-Feng Li, and Joong-Kee Lee
- Subjects
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HYDROGEN , *HYDROGEN-deuterium exchange , *EXCHANGE reactions , *METAL catalysts , *SPILLOVER (Chemistry) - Abstract
Hydrogen spillover mechanism of metal-supported covalent-organic frameworks COF-105 is investigated by means of the density functional theory, and the effects of metal catalysts M4 (Pt4, Pd4, and Ni4) on the whole spillover process are systematically analyzed. These three metal catalysts exhibit several similar phenomena: (i) they prefer to deposit on the tetra (4-dihydroxyborylphenyl) silane (TBPS) cluster with surface-contacted configuration; (ii) only the H atoms at the bridge site can migrate to 2,3,6,7,10,11-hexahydroxy triphenylene (HHTP) and TBPS surfaces, and the migration process is an endothermic reaction and not stable; (iii) the introduction of M4 catalyst can greatly reduce the diffusion energy barrier of H atoms, which makes it easier for the H atoms to diffuse on the substrate surface. Differently, all of the H2 molecules spontaneously dissociate into H atoms onto Pt4 and Pd4 clusters. However, the adsorbed H2 molecules on Ni4 cluster show two types of adsorption states: one activated state with stretched H–H bond length of 0.88 Å via the Kubas interaction and five dissociated states with separated hydrogen atoms. Among all the M4 catalysts, the orders of the binding energy of M4 deposited on the substrate and average chemisorption energy per H2 molecule are Pt4>Ni4>Pd4. On the contrary, the orders of the migration and diffusion barriers of H atoms are Pt4
- Published
- 2017
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