Contents lists available at ScienceDirect Microporous and Mesoporous Materials journal homepage: www.elsevier.com/locate/micromeso MoO 3 nanoparticle formation on zeolitic imidazolate framework-8 by rotary chemical vapor deposition Matteo Ciprian a , Peng Xu a , Somboon Chaemchuen a , Rong Tu a , Serge Zhuiykov b , Philippe M. Heynderickx b,d , Francis Verpoort a,b,c,* a State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan, China b Center for Environmental and Energy Research (CEER), Ghent University Global Campus, 119 Songdomunhwa-Ro, Yeonsu-Gu, Incheon 406-840, South Korea c National Research Tomsk Polytechnic University, Lenin Avenue 30, 634050 Tomsk, Russian Federation d Department of Green Chemistry and Technology (BW24), Faculty of Bioscience Engineering, Ghent University, 753 Coupure Links, Ghent B-9000, Belgium ARTICLE INFO Keywords: MoO 3 nanoparticles ZIF-8 Photocatalysis Rotary chemical vapor deposition ABSTRACT For the first time, MoO 3 nanoparticles (NPs) with a size ranging from 1.5 to 60 nm were deposited on spray dried zeolitic imidazolate framework-8 (ZIF-8) by rotary chemical vapor deposition (RCVD) in order to improve its photocatalytic performance. A direct effect of the deposition time on the metal oxide loading was observed. In a time frame between 0.9 and 2.7 ks the metal oxide loading can be increased from 1 to 3 wt%. All the MoO 3 -NPs/ ZIF-8 catalysts were tested towards the methylene blue photodegradation using sunlight. MoO 3 -NPs/ZIF-8 3 wt% RCVD reached a conversion of 82% and 95% after 180 and 300 min, respectively. 1. Introduction Zeolitic Imidazole Frameworks (ZIFs) [1,2] are an interesting sub- class of metal-organic frameworks (MOFs) having an extended 3D crystalline structure consisting of metal ions (e.g. Zn, Co, In) bridged in a tetrahedral fashion via the imidazolate linker. They combine the advantages of MOFs with higher stability and framework diversity. Zeolitic Imidazolate Framework 8 (ZIF-8), which is constructed with Zn (II) ions and 2-methylimidazole ligands, has received significant at- tention due to its high thermal stability in aqueous solutions [3], ap- plication in gas uptake and separation, as well as drug delivery [4–6]. Additionally, this new class of materials created an increasing attention as photocatalyst with promising results [7,8]. MOFs structural key feature is the highly tunable specific surface area and porosity, which with the encapsulation of active species and nanoparticles, can enhance their catalytic performances [9–11]. Titanium oxide (TiO 2 ) is an efficient photocatalyst under UV light and extensive research has been executed to modify its electronic structure by applying nanoparticles to improve the photo response under solar light radiation [12–15]. Among the n-type semiconductors, molybdenum oxide (MoO 3 ) is an ideal candidate as doping agent and has generated much research interest due to its wide application in various fields such as photoluminescence [16], optical fibers [17], scintillation materials [18] and photocatalyst for dye degradation [19,20]. A monolayer-dispersed MoO 3 on TiO 2 has been synthesized by impregnation technique [21], reaching pour performances. To further advance the photochromic properties, numerous strategies such as metalorganic decomposition [22], hydrothermal method [23], surfac- tant micelle nucleation [24] and sol-gel process [25] have been re- searched achieving MoO 3 -TiO 2 nanostructures with a significant im- provement. However, with these techniques, the use of surfactants and high temperature second stage thermal treatments are required. A new versatile technique is the rotary chemical vapor deposition (RCVD) [26,27]. This one step solvent free process is proven to be ef- fective towards a uniform nanoparticle deposition on powder supports [28–30]. The rotary reactor can ensure the contact between the pre- cursor gasses and the powder, in combination with a stable floating state and a uniform temperature distribution. In the present study, MoO 3 nanoparticles (NPs) were generated for the first time on spray dried ZIF-8 by RCVD at 250 °C using Mo(CO) 6 as precursor. Subse- quently, MoO 3 -NPs/ZIF-8 was characterized and its photocatalytic performance was evaluated against methylene blue degradation. 2. Experimental section 2.1. Materials Zinc acetate ((Zn(OAc) 2 ·2H 2 O); ≥99%), 2-methylimidazole (2- mIm; 98%), molybdenum oxide (MoO 3 ; 99.5%) and methylene blue (MB) were purchased from Aladdin Ltd. All reagents and solvents were https://doi.org/10.1016/j.micromeso.2018.03.028 Received 18 January 2018; Received in revised form 7 March 2018; Accepted 24 March 2018 * Corresponding author. State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan, China. E-mail address: Francis.verpoort@ugent.be (F. Verpoort). Microporous and Mesoporous Materials 267 (2018) 185–191 Available online 29 March 2018 1387-1811/ © 2018 Elsevier Inc. All rights reserved. T