Robust and efficient catalyst derived from bimetallic Zn/Co zeolitic imidazolate frameworks for CO 2 conversion Somboon Chaemchuen a,b , Xuan Xiao a,c , Marzieh Ghadamyari a,c , Bibimaryam Mousavi a , Nikom Klomkliang d , Ye Yuan a,⇑ , Francis Verpoort a,b,c,e,⇑ a Laboratory of Organometallics, Catalysis and Ordered Materials, State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan, China b National Research Tomsk Polytechnic University, Lenin Avenue 30, 634050 Tomsk, Russian Federation c School of Materials Science and Engineering, Wuhan University of Technology, Wuhan 430070, China d School of Chemical Engineering, Suranaree University of Technology, Nakhon Ratchasima 30000, Thailand e College of Arts and Sciences, Khalifa University of Science and Technology, PO Box 127788, Abu Dhabi, United Arab Emirates article info Article history: Received 2 October 2018 Revised 18 November 2018 Accepted 21 November 2018 Keywords: Bi-metallic ZIF Pyrolysis CO 2 conversion Heterogeneous catalysis Cyclic carbonates abstract A robust catalyst generated from the pyrolysis of bimetallic Zn/Co-ZIF comprising magnetic properties demonstrated to be an effective heterogeneous catalyst system for CO 2 conversion reaction without the need of co-catalyst and solvent. Controllable pyrolysis under various conditions resulted in a unique active structure composed of metallic particles stabilized in a nitrogen-doped carbon matrix. The metallic particles acting as acid sites are dispersed in a nitrogen-doped porous carbon-wall which provides the basic sites. These sites are created during the pyrolysis process of Zn/Co-ZIF used as a special template under a controlled atmosphere. The resulting material possessing both, acid and basic sites, showed an excellent catalytic performance for the cycloaddition of CO 2 into epoxides as these sites correspond to the active sites in the catalytic cycle. Additional, the pyrolysis conditions indicated to play an important role in the properties of the resulting materials and in parallel with the catalytic performance. The cat- alytic material proved to be very robust and maintained high activities for at least eleven cycles using the optimized reaction condition. Moreover, the magnetic property of the resulting catalyst is advanta- geous especially for the separation from the reaction mixture. Ó 2018 Elsevier Inc. All rights reserved. 1. Introduction Utilization of carbon dioxide (CO 2 ) as a carbon source has received extensive attention in research societies aiming to reduce CO 2 emission which is the main cause of global warming [1,2]. Among the CO 2 utilization reactions, the CO 2 chemical fixation, producing carbonates is an economical attractive reaction pathway and remediates the environment of CO 2 emission. Numerous cyclic carbonates are widely applied as electrolytes in Li-ion batteries, aprotic solvents for cosmetics, and intermediates in pharmaceuti- cal and polymer synthesis, etc. [3,4]. Furthermore, several reports describe MOFs as efficient heterogeneous catalysts converting CO 2 to value-added chemicals in absence of solvent and co- catalyst [5,6]. Tailoring the MOF structures via metals ions/clusters and specifically designed organic linkers provides advanced prop- erties such as high CO 2 uptake, permanent porosity, and active cat- alytic sites, etc. [7]. The Zn-based ZIFs (ZIF-8, ZIF-90, ZIF-68, etc.) were among the first MOFs to be applied as a catalyst for the con- version of CO 2 with an epoxide to produce cyclic carbonates. How- ever, these systems suffered from low selectivity and reusability [8,9]. Later on, Co-based MOFs were found to be active for this reaction as well, however, they exhibited lower conversion rates than their Zn-based MOF analogous. Recently, a bimetallic Zn/Co- ZIF was developed via a simple synthesis method to synthesize a bimetallic MOF with Zn and Co as metal centers which showed enhanced gas adsorption properties [10,11]. Moreover, from all reported catalytic MOF materials, the bimetallic Zn/Co-ZIF exhib- ited a high catalytic conversion of epoxide to carbonates using CO 2 as a C1 source with excellent selectivity and performance [10]. Nevertheless, MOFs applied as heterogeneous catalysts pos- sess a relatively low chemical/thermal stability and combined with their small particle size, these drawbacks have to be considered for large-scale or industrial applications. Moreover, small particle- https://doi.org/10.1016/j.jcat.2018.11.027 0021-9517/Ó 2018 Elsevier Inc. All rights reserved. ⇑ Corresponding authors at: Laboratory of Organometallics, Catalysis and Ordered Materials, State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan, China (F. Verpoort). E-mail address: Francis.verpoort@ugent.be (F. Verpoort). Journal of Catalysis 370 (2019) 38–45 Contents lists available at ScienceDirect Journal of Catalysis journal homepage: www.elsevier.com/locate/jcat