Metal-organic framework encapsulated single-atom Pt catalysts for efficient photocatalytic hydrogen evolution

Atomically dispersed metal catalysts have emerged as a new research frontier in the catalytic community due to the utmost atom efficiency and tunable functionality in a wide variety of catalytic reactions. In the present work, a general operable synthetic platform for stable and well-defined positioned single-atom metal catalysts encapsulated in metal-organic framework (MOF) architecture was developed. Using the MOF-808 based single ion trap method, single metal ions were effectively captured by ethylenediaminetetraacetic acid (EDTA) ligands, which were exchanged with the original formate ligands anchored at the Zr-6 cluster metal nodes. Upon activated in hydrogen atmosphere at 200 degrees C, the stable MOF-808-EDTA encapsulated single-atom metal catalysts with well-defined atomic positions were synthesized. The synthesized single-atom metal catalysts were confirmed using various experimental characterization techniques including high-angle annular dark-field scanning transmission electron microscope, extended X-ray absorption fine structure spectroscopy analysis, and diffuse reflectance infrared Fourier transform, as well as theoretical density functional theory calculations. As a demonstration case, it has been found that the as-synthesized MOF-808-EDTA encapsulated single-atom Pt catalyst shows the excellent photocatalytic hydrogen evolution activity (68.33 mmol g(-1) h(-1)) and high stability. The apparent quantum efficiency reaches up to 67.6% at 420 nm. This work not only provides a general and effective synthesis approach for preparing stable, uniformly distributed, MOF encapsulated single-atom metal catalysts such as Pd, Rh, Ru, Cu, Co, and Ni, but also sheds new insights into single-atom metal catalysts for photocatalytic water splitting for hydrogen production. (C) 2019 Elsevier Inc. All rights reserved.