Scaling-Up Microwave-Assisted Synthesis of Highly Defective Pd@UiO-66-NH2 Catalysts for Selective Olefin Hydrogenation under Ambient Conditions

Raúl M Guerrero; Ignacio D Lemir; Sergio Carrasco; Carlos Fernández-Ruiz; Safiyye Kavak; Patricia Pizarro; David P Serrano; Sara Bals; Patricia Horcajada; Yolanda Pérez

doi:10.1021/acsami.4c03106

Scaling-Up Microwave-Assisted Synthesis of Highly Defective Pd@UiO-66-NH₂ Catalysts for Selective Olefin Hydrogenation under Ambient Conditions

ACS Appl Mater Interfaces. 2024 Apr 26;16(18):24108-24121. doi: 10.1021/acsami.4c03106. Online ahead of print.

Authors

Raúl M Guerrero^{1

2}, Ignacio D Lemir^{1

2}, Sergio Carrasco¹, Carlos Fernández-Ruiz^{1

2}, Safiyye Kavak³, Patricia Pizarro^{2

4}, David P Serrano^{2

4}, Sara Bals³, Patricia Horcajada¹, Yolanda Pérez^{1

5}

Affiliations

¹ Advanced Porous Materials Unit, IMDEA Energy Institute, Avda. Ramón de la Sagra, 3, Móstoles 28935, Madrid, Spain.
² Thermochemical Processes Unit, IMDEA Energy Institute, Avda. Ramón de la Sagra, 3, Móstoles 28935, Madrid, Spain.
³ EMAT and NANOlab Center of Excellence, University of Antwerp, Groenenborgerlaan 171, Antwerp 2020, Belgium.
⁴ Chemical and Environmental Engineering Group, Rey Juan Carlos University, C/Tulipán, s/n, Móstoles 28933, Madrid, Spain.
⁵ COMET-NANO Group, ESCET, Universidad Rey Juan Carlos, C/Tulipán, s/n, Móstoles 28933, Madrid, Spain.

Abstract

The need to develop green and cost-effective industrial catalytic processes has led to growing interest in preparing more robust, efficient, and selective heterogeneous catalysts at a large scale. In this regard, microwave-assisted synthesis is a fast method for fabricating heterogeneous catalysts (including metal oxides, zeolites, metal-organic frameworks, and supported metal nanoparticles) with enhanced catalytic properties, enabling synthesis scale-up. Herein, the synthesis of nanosized UiO-66-NH₂ was optimized via a microwave-assisted hydrothermal method to obtain defective matrices essential for the stabilization of metal nanoparticles, promoting catalytically active sites for hydrogenation reactions (760 kg·m^-3·day^-1 space time yield, STY). Then, this protocol was scaled up in a multimodal microwave reactor, reaching 86% yield (ca. 1 g, 1450 kg·m^-3·day^-1 STY) in only 30 min. Afterward, Pd nanoparticles were formed in situ decorating the nanoMOF by an effective and fast microwave-assisted hydrothermal method, resulting in the formation of Pd@UiO-66-NH₂ composites. Both the localization and oxidation states of Pd nanoparticles (NPs) in the MOF were achieved using high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and X-ray photoelectron spectroscopy (XPS), respectively. The optimal composite, loaded with 1.7 wt % Pd, exhibited an extraordinary catalytic activity (>95% yield, 100% selectivity) under mild conditions (1 bar H₂, 25 °C, 1 h reaction time), not only in the selective hydrogenation of a variety of single alkenes (1-hexene, 1-octene, 1-tridecene, cyclohexene, and tetraphenyl ethylene) but also in the conversion of a complex mixture of alkenes (i.e., 1-hexene, 1-tridecene, and anethole). The results showed a powerful interaction and synergy between the active phase (Pd NPs) and the catalytic porous scaffold (UiO-66-NH₂), which are essential for the selectivity and recyclability.

Keywords: UiO-66-NH2; defect engineering; gram-scale; microwave-assisted synthesis; palladium; selective hydrogenation.