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Article Cite This: Inorg. Chem. XXXX, XXX, XXX−XXX

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High Selectivity of Hydrogenation Reaction over Co0.15@C/PC Catalyst at Room Temperature Ruirui Yun,*,† Wanjiao Ma,† Suna Wang,‡ Weiguo Jia,† and Baishu Zheng§

Inorg. Chem. Downloaded from pubs.acs.org by UNIV OF LOUISIANA AT LAFAYETTE on 04/23/19. For personal use only.

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The Key Laboratory of Functional Molecular Solids, Ministry of Education, College of Chemistry and Materials Science, Anhui Normal University, Wuhu 214001, P. R. China ‡ Shandong Provincial Key Laboratory of Chemical Energy Storage and Novel Cell Technology, School of Chemistry and Chemical Engineering, Liaocheng University, Liaocheng 252059, P. R. China § Key Laboratory of Theoretical Chemistry and Molecular Simulation of Ministry of Education, School of Chemistry and Chemical Engineering, Hunan University of Science and Technology, Xiangtan 411201, China S Supporting Information *

ABSTRACT: In the field of catalysis, material scientists pay much attention to tuning the activity and chemoselectivity of metal nanoparticles. Herein, we design and successfully synthesize a series of Co NPs which show high performance on hydrogenation of nitroarenes with both activity and chemoselectivity. Co0.15@C/PC preferentially activates the −CO bond over −NO2 in water with ammonia borane (AB); however, when the hydrogen source is changes to hydrazine hydrate (HH), the results are the opposite. The Co-based catalyst exhibits exceptionally high catalytic activity (with a TOF value of 10512 h−1, which is approximately 100 times than the akin catalysts) and chemo-selectivity for the hydrogenation of nitro compounds under mild conditions. Additionally, the catalyst can be separated easily by a magnet and shows prominent stabilit, which means that it can be reused for at least 10 cycles.

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kinds of hydrogenation, such as CC,19−21 −NO21,22,23 and CO24,25 bonds. But Co and Ni tend to aggregate at high temperature, which causes the decrease of the specific surface area and of the active site of the catalyst. Recently, many studies have reported some ways to solve this crucial issue. Fu and co-workers successfully loaded cobalt onto ZrLa0.2OX, for which good dispersion and large specific surface area cause it to have excellent catalytic performance.26 Beller’s group reported a simple way to obtain an efficient hydrogen material by applying a nitrogen-doped titania-supported Co catalyst.27,28 These methods well solved the problem of dispersion, and the catalytic performance was greatly improved. But the only disadvantage is that they still use H2. Consequently, it is very necessary to find a catalyst with simple synthesis, mild catalytic conditions, and high hydrogenation selectivity. However, some of the shortcomings are also not negligible, such as aggregation during the synthesis process, requirement of harsh conditions, and poor selectivity in the process of catalytic reaction. Therefore, it is important to design a synthetic way to overcome the problem of aggregation while increasing specific area and active sites to improve the reaction conditions and enhance catalytic selectivity.29−31 On the basis of the above considerations, in this work, we present a novel D-glucose-assisted pyrolysis strategy to

INTRODUCTION Metal catalysts supported by a porous medium have been extensively used in the chemical industry for many kinds of reactions.1,2 In the field of heterogeneous catalysis, how to obtain metal catalysts with high activity and chemo-selectivity has attracted tremendous attention.3,4 In particular, selective hydrogenation of aldehydes, ketones, and nitro compounds plays a crucial role in the field of industry chemistry. The selective reduction of functionalized nitroarene to amino compounds is a significant process, mainly in agricultural chemistry, pigment chemistry, and pharmacochemistry.5,6 To obtain high performance catalysts with selectivity and high activity has been the basic concept. Accordingly, numerous methods have been used to construct high-efficiency catalysts, such as heteroatom doping and multimetallic synergistic reactions.7−9 Recently, there have been many reports about selective catalytic preparation of aldehydes, ketones, and nitro compounds from alcohol and amine compounds in noble metal catalysts, respectively, but the restricted reserves and high cost limited their extensive application, so the sustainable use of resources, especially with non-noble metal catalysts, have attracted the attention of an increasing number of researchers.10,11 Nonnoble metals such as iron, cobalt, and nickel are not only abundant on the earth, but also have superior properties in terms of catalysis.12−14 Co15,16 and Ni17,18 nano particles and single atom are versatile catalysts in various catalytic reactions, including all © XXXX American Chemical Society

Received: February 12, 2019

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DOI: 10.1021/acs.inorgchem.9b00385 Inorg. Chem. XXXX, XXX, XXX−XXX

Article

Inorganic Chemistry Scheme 1. Synthesis Method of Con@C/PC Catalyst

Figure 1. (a) HTEM image and EDS-mapping of Co0.15@C/PC; (b) wide-range XPS spectrum; (c) XPS survey spectrum for Co0.15@C/PC with two main broad peaks at 777.79 and 792.86 eV, assigned to Co 2p1/2 and Co 2p3/2, respectively. of deionized water and stirred 30 min by ultrasonic means. The mixture solution was heated at 100 °C for 20 min to form a purple sol and dried under vacuum 80 °C overnight to form a purple powder. The obtained purple powder was placed in a pipe heater and heated to 700 °C under Ar gas atmosphere for 1 h, with that naturally cooling to ordinary temperature. Characterization of Samples. Powder XRD pattern was carried out with a Bruker D8 X-ray diffractometer with monochromatized Cu Kα radiation (λ = 1.5418 Å). Transmission electron microscope (TEM) and high-resolution TEM observations were acquired on JEOL-2011 with an electron acceleration energy of 200 kV. The content of Co in the catalysts was determined by an Optima 7300 DV inductively coupled plasma atomic emission spectrometer (ICP-AES). X-ray photoelectron spectroscopy (XPS) was performed on a ULVAC

construct Con@C nanoparticles which were highly dispersed on porous carbon (PC). The as-synthesized Con@C/PC (n: represents the cobalt contents) can selectively catalyze liquid-phase hydrogenation of aldehydes, ketones, and nitro compounds in different hydrogen sources at normal pressure and temperature. We demonstrate that the hydrogen source hydrazine hydrate is preferred for selective hydrogenation of nitro compounds while ammonia borane is preferred for aldehydes.

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EXPERIMENTAL SECTION

Sample Preparation. For the synthesis of Con@C/PC, 0.4 g of cobalt nitrate hexahydrate and 2 g of D-glucose were added into 10 mL B


Article

Inorganic Chemistry

characterized by gas chromatography with n-hexadecane as an external standard. The identity of the products was further determined by gas chromatography−mass spectrometry (GC-MS) measurements with n-dodecane as standard.

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RESULTS AND DISCUSSION In this research, different kinds of Con@C/PC catalysts were fabricated just as Scheme 1 illustrates. For comparison, the effect of catalytic performance was investigated by the amount of Co, pyrolysis temperature, and pyrolysis times. X-ray powder diffraction (XRD) patterns confirm the Con@C/PC phase (PDF No. 15-0806). The peaks at 44.2°, 51.5°, and 75.8° can be designated to the (100), (200), and (220) lattice planes of Co nanoparticle (Figure S1). High-resolution transmission electron microscopy (HTEM) shows that Co NPs were encapsulated in carbon and were well dispersed on the porous carbon (Figure 1a). All the elements including C and Co have homogeneous distribution, as demonstrated by the energy-dispersive X-ray spectroscopy (EDX) element mapping images (Figure 1a). The selected area electron diffraction (SAED) suggested that all the clear diffraction rings matched well with Co nanoparticles (inset of Figure 1a). The Co content in Con@C/PC catalyst is in the range of 3.80−20.00% (determined by ICP-AES, Table S1), and it was studied with different temperatures and pyrolysis times. The states of Co atom of Con@C/PC were characterized by X-ray photoelectron spectroscopy (XPS) (Figure 1, parts b and c). The peaks at 777.79 and 792.86 eV can be assigned to Co0. The Raman spectrum was used to identify the change of graphitic carbon (Figure S2). Notably, the band with intensity at ∼1336.3 is attributed to defective sp3 hybridized carbon (D band) and 1594.9 cm−1 can be assigned to the crystallized graphitic sp2

Figure 2. Performance of hydrogenation of nitrobenzene with a series of Co-based catalysts (catalytic reaction with hydrazine hydrate as hydrogen resource under room temperature). PHI Quantera microscope. The surface area of the samples was estimated by the method of Brunauer−Emmett−Teller (BET), and the pore size distribution was obtained from the DFT method in the Micrometrics ASAP2020 software package based on the N2 sorption at 77 K. Catalytic Hydrogenation Activity Test. All hydrogenation reactions were placed in a 25 mL bottle and a magnetic stirrer. In the reaction, 0.5 mmol of reactant and 10 mg of catalyst and HH or AB were mixed in 5 mL of water and alcohol (1:4). The reaction was carried at normal pressure and room temperature. The products were

Table 1. Reduction of Various Nitroarenes by Co0.15@C/PCa

a

Analyzed by GC-MS spectrum with n-dodecane as standard; rt = room temperature. C


Article

Inorganic Chemistry Table 2. Hydrogenation of Different Aldehydes by Co0.15@C/PCa

a

Note: AB is ammonia borane. R represented as alkyl or unsaturated chain hydrocarbon. NPT is normal pressure and temperature.

carbon (G band), respectively. The ID/IG relative ratio of 0.84 also confirms defection of the carbon, which is good to favor rapid mass transfer and can offer adequate active site exposure for catalysis. Just as Figure S3, S4, and S5 show, the catalyst shows rich mesoporous pores. The N2 sorption isotherm of the Co0.15@C/PC sample showed a typical IV isotherm, which revealed a mesoporous characteristic. The calculated total pore volume and the BET surface area of Co0.15@C/PC were 0.19 cm3/g and 373 m2/g (Figure S6), respectively. The catalytic performance of Con@C/PC was evaluated via the hydrogenation of nitro compounds by hydrazine hydrate as hydrogen resource. The products of such a reaction can be simply analyzed by GC−MS. As shown in Figure 2, catalytic reduction of nitrobenzene was chosen as a benchmark substrate. It is notable that the nitrobenzene is quickly converted to aniline within 20 min. The results show that the Co contents strikingly boosted the efficiency during the catalytic reaction. One of the series catalysts, Co0@C/PC, does not give the target results. However, the catalyst Co0.03@C/PC shows about 12% conversion which is much higher than that of Co0@ C/PC under the same reaction conditions. Furthermore, the conversion is increased when the contents of Co are increased; significantly, Co0.15@C/PC achieves the maximum performance. The catalyst exhibits exceptionally high catalytic activity (10512 h−1 which is about 100 times higher than that for similar kinds of catalysts, Table S2). The results illustrate that well-dispersed mesoscale porosity was constructed in the synthesis procedure of the catalysts, and the pores made Co0.15@ C/PC fit for mass transfer of the substrate; besides this, the

size of Co NPs and the dispersity are more important for the catalytic performance.32−35 In consideration of the fact that the catalyst Co0.15@C/PC shows admirable catalytic performance, the hydrogenation of different kinds of nitroarenes are implemented. We can see from Table 1 that the catalyst enabled the hydrogenation of multifarious substituted nitro compounds, obtaining the corresponding anilines with perfect conversions and chemoselectivity. More importantly, the halogenated nitrobenzene gave high content of the target products without dehalogenation. It is worth mentioning that the catalyst expresses high chemo-selectivity in the hydrogenation of functional nitroarenes, such as ester, carboxyl, carbonyl, and cyano, giving the corresponding anilines in about 99% conversion without any byproducts. These outstanding results highlight the chemoselectivity of the Co-based catalyst, showing its eminent virtue compared to that of precious metal-based catalysts. More interestingly, the catalyst can perform hydrogenation for a variety of aldehydes selectively when the hydrogen resource changes to ammonia borane at room temperature (Table 2). The stability of catalyst is a vital benchmark to evaluate the performance of catalyst, which is crucial for practical productions. We can see from Figure 3 that, to demonstrate the stability and reusability of Co0.15@C/PC, cyclic experiments for the reduction of nitrobenzene were carried out. The catalyst Co.015@C/PC keeps its phase after being reused 11 times (Figure S7, Supporting Information). Interestingly, the catalyst can be simply recovered by a magnet due to its stronger magnetic ability. D


Article

Inorganic Chemistry

Photocatalytic and Electrocatalytic Reactions. Appl. Catal., B 2018, 227, 386. (2) Yuan, Y.-J. Metal-complex Chromophores for Solar Hydrogen Generation. Chem. Soc. Rev. 2017, 46, 603−631. (3) Hakim Siddiki, S. M. A.; Toyao, T.; Shimizu, K. Acceptorless Dehydrogenative Coupling Reactions with Alcohols over Heterogeneous Catalysts. Green Chem. 2018, 20, 2933. (4) Song, T.; Ren, P.; Duan, Y.; Wang, Z.; Chen, X.; Yang, Y. Cobalt Nanocomposites on N-doped Hierarchical Porous Carbon for Highly Selective Formation of Anilines and Imines from Nitroarenes. Green Chem. 2018, 20, 4629. (5) Yang, J.; Yuan, M.; Xu, D.; Zhao, H.; Zhu, Y.; Fan, M.; Zhang, F.; Dong, Z. Highly Dispersed Ultrafine Palladium Nanoparticles Encapsulated in A Triazinyl Functionalized Porous Organic Polymer as A Highly Efficient Catalyst for Transfer Hydrogenation of Aldehydes. J. Mater. Chem. A 2018, 6, 18242. (6) Lei, L.; Wu, Z.; Liu, H.; Qin, Z.; Chen, C.; Luo, L.; Wang, G.; Fan, W.; Wang, J. A Facile Method for the Synthesis of GrapheneLike 2D Metal Oxides and Their Excellent Catalytic Application in the Hydrogenation of Nitroarenes. J. Mater. Chem. A 2018, 6, 9948. (7) Abhilash, M.; Alex, M.; Mathews, V.; Nair, R. H. Chronic Effect of Aspartame on Ionic Homeostasis and Monoamine Neurotransmitters in the Rat Brain. Int. J. Toxicol. 2014, 33, 332. (8) Villaverde, M.; Bertero, N.; Garetto, T.; Marchi, A. Selective Liquid-phase Hydrogenation of Furfural to Furfuryl Alcohol over Cubased Catalysts. Catal. Today 2013, 213, 87. (9) Zhao, F.; Ikushima, Y.; Chatterjee, M.; Shirai, M.; Arai, M. An Effective and Recyclable Catalyst for Hydrogenation of α,βunsaturated Aldehydes into Saturated Aldehydes in Supercritical Carbon Dioxide. Green Chem. 2003, 5, 76. (10) Rautenstrauch, V.; Hoang-Cong, X.; Churlaud, R.; AbdurRashid, K.; Morris, H. R. Hydrogenation Versus Transfer Hydrogenation of Ketones: Two Established Ruthenium Systems Catalyze Both. Chem. - Eur. J. 2003, 9, 4954. (11) Zanotti-Gerosa, A.; Groarke, M.; Hems, W. P. Ketone Hydrogenation Technology. Speciality Chemicals Magazine 2004, 24, 42−43. (12) Jagadeesh, R. V.; Surkus, A.-E.; Junge, H.; Pohl, M.-M.; Radnik, J.; Rabeah, J.; Huan, H.; Schünemann, V.; Brückner, A.; Beller, M. Nanoscale Fe2O3-based Catalysts for Selective Hydrogenation of Nitroarenes to Anilines. Science 2013, 342, 1073. (13) Camacho-Bunquin, J.; Ferrandon, M.; Sohn, H.; Yang, D.; Liu, C.; Ignacio-de Leon, P. A.; Perras, F. A.; Pruski, M.; Stair, P. C.; Delferro, M. Chemoselective Hydrogenation with Supported Organoplatinum(IV) Catalyst on Zn(II)-modified Silica. J. Am. Chem. Soc. 2018, 140, 3940. (14) Peng, Y.; Geng, Z.; Zhao, S.; Wang, L.; Li, H.; Wang, X.; Zheng, X.; Zhu, J.; Li, Z.; Si, R.; Zeng, J. Pt Single Atoms Embedded in the Surface of Ni Nanocrystals as highly Active Catalysts for Selective Hydrogenation of Nitro Compounds. Nano Lett. 2018, 18, 3785. (15) Li, Y. H.; Hu, Y. Y.; Wu, X.-F. Non-noble Metal-catalysed Carbonylative Transformations. Chem. Soc. Rev. 2018, 47, 172. (16) Wang, X.; He, Y.; Liu, Y.; Park, J.; Liang, X. Atomic Layer Deposited Pt-Co Bimetallic Catalysts for Selective Hydrogenation of α, β-unsaturated Aldehydes to Unsaturated Alcohols. J. Catal. 2018, 366, 61. (17) Giziński, D.; Goszewska, I.; Zieliński, M.; Lisovytskiy, D.; Nikiforov, K.; Masternak, J.; Zienkiewicz-Machnik, M.; Śrębowata, A.; Sá, J. Chemoselective Flow Hydrogenation of α, β-unsaturated Aldehyde with Nano-nickel. Catal. Commun. 2017, 98, 17. (18) Jeong, H.; Kim, C.; Yang, S.; Lee, H. Selective Hydrogenation of Furanic Aldehydes using Ni Nanoparticle Catalysts Capped with Organic Molecules. J. Catal. 2016, 344, 609. (19) Chirik, P. J. Iron- and Cobalt-catalyzed Alkene Hydrogenation: Catalysis with both Redox-active and strong Field Ligands. Acc. Chem. Res. 2015, 48, 1687.

Figure 3. Recyclability tests of Co0.15@C/PC (inset: conversion of nitrobenzene to aniline).

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CONCLUSIONS In conclusion, a novel and efficient strategy has been designed for preparing high dispersive cobalt NPs which are encapsulated in porous graphic carbon. The catalyst Co@C/PC shows outstanding catalytic activity (TOF is 10512 h−1) and chemo-selectivity in the hydrogenation for nitrobenzene, because the large specific surface areas of porous carbon and the sizes of Co NPs are well-distributed. Meanwhile, the catalytic performance and chemo-selectivity of Co nanoparticles are successfully tuned by the amount of D-glucose. Furthermore, the catalyst could be reused many times without overt reduction of catalytic performance and can be easily separated from the reaction solution because of its magnetic properties. The results give a simple and low-cost method to design and synthesize versatile metals@carbon catalysts in the catalytic reaction.

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ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.inorgchem.9b00385. Materials and instrumentation, characterization, and GC graphics (PDF)

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected] (R.Y.). ORCID

Ruirui Yun: 0000-0002-5598-5076 Weiguo Jia: 0000-0001-7976-7543 Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS Our work was funded by the National Natural Science Foundation of China (No. 21401004 and 21571092), the Natural Science Foundation of Anhui Province (No. 1508085QB36), and the National Creative Plan of Students (201810370443).

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