Ligand-Functionalization-Controlled Activity of Metal-Organic Framework-Encapsulated Pt Nanocatalyst toward Activation of Water.

Ogiwara, Naoki; Kobayashi, Hirokazu; Inukai, Munehiro; Nishiyama, Yusuke; Concepción, Patricia; Rey, Fernando; Kitagawa, Hiroshi · Nano Lett · 2020

basic_science · Level V

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Abstract

We first report the systematic control of the reactivity of H<sub>2</sub>O vapor in metal-organic frameworks (MOFs) with Pt nanocrystals (NCs) through ligand functionalization. We successfully synthesized Pt NCs covered with a water-stable MOF, UiO-66 (Pt@UiO-66), having different metal ions or functionalized ligands. The ligand functionalization of UiO-66 significantly affected the catalytic performance of the water-gas shift reaction, and the replacement of Zr<sup>4+</sup> ions with Hf<sup>4+</sup> ions in UiO-66 had no impact on the catalytic activity. The introduction of a -Br group lowered the reactivity of Pt@UiO-66 by nearly half, whereas the substitution of -Br with a -Me<sub>2</sub> group triply enhanced the activity. The origin of the enhanced catalytic activity was found to be the change in H<sub>2</sub>O activity in the UiO-66 pores by the ligand functionalization, which was investigated using H<sub>2</sub>O sorption, solid-state NMR, X-ray photoelectron spectroscopy, and in situ IR measurements. This work opens a new prospect to develop MOFs as a platform to activate H<sub>2</sub>O.