Fabrication of Magnetic Pd/MOF Hollow Nanospheres with Double-Shell Structure: Toward Highly Efficient and Recyclable Nanocatalysts for Hydrogenation Reaction

Abstract

MNPs@MOF catalysts obtained by encapsulating metal nanoparticles (NPs) into metal–organic frameworks (MOFs) show fascinating performance in heterogeneous catalysis. The improvement of catalytic activity and reusability of MNPs@MOF catalysts has been a great challenge for a long time. Herein, we demonstrate well-designed Pd/MOFs, featuring hollow double-shell structure and magnetic property, exhibiting high reusability, efficient catalytic activity, and size selectivity for hydrogenation reaction. The as-synthesized Pd/MOF, denoted as Void nFe3O4@Pd/ZIF-8@ZIF-8, possesses diverse functional structural features. The hollow cavity can improve mass transfer; superparamagnetic Fe3O4 NPs embedded in the inner MOF shell can enhance the separation and recyclability; Pd NPs are highly dispersed in the matrix of the inner MOF shell, and the outer MOF shell acts as a protector to prevent the leaching of Pd NPs and a sieve to achieve size selectivity. As a proof of concept, the Void nFe3O4@Pd/ZIF-8@ZIF-8 catalyst exhibited excellent performance for the hydrogenation of styrene at room temperature. The activity only reduced 10% after 20 cycles for the higher conversions (>90%), and the lower conversion only decreased 3.6% (from 32.5 to 28.9% conversion) after twenty consecutive cycles, indicating the good and intrinsic reusability of the catalyst. The proposed structure in this work provides a strategy to effectively improve the reusability of MNPs@MOF catalysts, which would increase their practical applications.

A p-n Heterojunction Based Pd/PdO@ZnO Organic Frameworks for High-Sensitivity Room-Temperature Formaldehyde Gas Sensor

“…The other three peaks, 337, 340.4, and 342.4 eV, and one satellite peak at 344.4 eV, were attributed to the 3d 5/2 and 3d 3/2 PdO and PdO/Pd, indicating that the surface of Pd-NPs is partially oxidized because of the exposure to the air. Therefore, the chemical state of palladium was Pd 0 and Pd 2+, corresponding to Pd and PdO, respectively ( Yamamoto et al, 1997 ; Zhong et al, 2019 ).…”

Step by Step Construction of Multifunctional Hollow Double Shell MNPs@MOF as a Powerful Tandem/Cascade Catalyst

“…>99%). This result was attributed to the presence of SPS which made SPS|(Au)ZIF-8|ZIF-8 similar to (Au) ZIF-8 without obvious hollow accelerated mass transfer effect (Zhong et al, 2019). Additionally, the slight dissolution of SPS in the reaction system would greatly hinder the delivery of the reaction substrate and reduce the contact frequency of the reaction substrate with the catalytic active center in unit time.…”

“…Sequentially, the outer ZIF-8 shell was grown stepwise on the surface of SPS|(Au)ZIF-8 to obtain SPS|(Au)ZIF-8|ZIF-8. Eventually, the hollow Void|(Au)ZIF-8|ZIF-8 was constructed by removing the hard template SPS ( Wan et al, 2017 ; Zhong et al, 2019 ).…”

“…In view of this, we predict that the structure and property of Au/MOFs can be further optimized to improve the TOF values, and even to make the reaction conditions more moderate and economical. As well known, the hollow structure has been demonstrated to enhance the catalytic performance of catalysts due to the unique role in accelerating mass transfer at the nano-scale ( Zhong et al, 2019 ; Wan et al, 2017 ). In addition, some MOFs possess basic active sites ( Zhang et al, 2020 ), which can avoid using alkaline auxiliaries to make the reaction conditions more mild and economical.…”

Advances in Functional Metal‐Organic Frameworks Based On‐Demand Drug Delivery Systems for Tumor Therapeutics

“…The magnetic properties of MOFs have been a receiving interest due to the integration of both magnetic properties and various MOF features into one material. [ 100–102 ] For example, an Fe 3 O 4 ‐decorated MOF loaded with nimesulide (a drug) exhibited magnetic resonance imaging and controlled drug release for treatment of pancreatic cancer. [ 60 ] In contrast, another magnetically responsive MOF‐based delivery composite for magnetic targeting and nuclear magnetic imaging was also developed for both in vitro and in vivo cancer therapy.…”