Supporting Information

Transcription

1 Supporting Information Au-HKUST-1 Composite Nanocapsules: Synthesis with a Coordination Replication Strategy and Catalysis on CO Oxidation Yongxin Liu, 1 Jiali Zhang, 1 Lingxiao Song, 1 Wenyuan Xu, 1 Zanru Guo, 1 Xiaomin Yang, 1 Xiaoxin Wu, 1 Xi Chen* 1 1. Department of Polymer Materials and Chemical Engineering, East China Jiaotong University, Nanchang , PR China Corresponding author s chenxi@ecjtu.edu.cn S-1

2 1. Materials and Instrumentation Copper chloride hydrate (CuCl2 2H2O, 99.0%), sodium hydroxide (NaOH, 96%), ethanol (99.7%), sodium citrate (99.0%), benzene-1, 3, 5-tricarboxylic acid (H3btc, 98%), ascorbic acid (99.99%) and chloroauric acid (HAuCl4, Au 47.8%) were purchased from Chinese domestic suppliers. Polyvinylpyrrolidone (PVP, Mw = 40000, reagent grade) was purchased from VETEC, Sigma-Aldrich. All chemicals were used as received without further purification. Ultra-pure water with resistivity larger than 18.0 MΩ was produced from an Ultrapure Water System (Purifier). Powder X-ray diffraction (XRD) was performed on a Bruker D8 Focus diffractometer with Cu Kα radiation and a Lynx Eye detector at a scanning rate of 10 min 1 in the 2θ range of 5 to 80. Field emission scanning electron microscopy (FESEM) images were taken using a Hitachi S-4800 scanning electron microscope. Transmission electron microscopy (TEM) images were taken using an FEI Tecnai F20 transmission electron microscopy operated at an accelerating voltage of 200 kv. 2. Synthesis of octahedral Cu2O nanocrystals. Octahedral Cu2O nanocrystals were synthesized following the procedure of Wang et al. with minor modifications. 1 Typically, 5 ml of an aqueous solution of NaOH (2.0 M) was added dropwise into 50 ml of a mixture solution containing CuCl2 2H2O (10 mm), sodium citrate (3.4 mm) and PVP (0.034 g ml 1 ) under stirring. After 0.5 h, 5 ml of an ascorbic acid solution (0.6 M) was added dropwise (5 minutes to complete) into the above solution. The resultant suspension was further aged for 3 hours. The products were dispersed in 40 ml of ethanol for the synthesis of Cu2O-Au composites. 3. Synthesis of Cu2O Au heterostructures. 1 ml of 1 mm HAuCl4 4H2O ethanol solution was added into 1 ml of above Cu2O ethanol solution. The mixtures were immediately shaken for 5 seconds and allowed to standing for 55 seconds. The products were collected by centrifugation at 8000 rpm for 1 minute and washed with ethanol several times. As illustrated in Fig. S1, the loading of the Au particles on the surface of Cu2O crystals could be increased by increasing the concentration of HAuCl4 4H2O ethanol solution. Finally, the products were dispersed in 1 ml of ethanol for the preparation of Cu2O Au-HKUST-1 core-shell S-2

3 heterostructures. 4. Synthesis of Cu2O Au-HKUST-1 core-shell heterostructures. 0.5 ml of 1, 3, 5-trimesic acid (H3btc) ethanol solution (160 mm) and 0.5 ml of N, N-dimethylacetamide were mixed with 1 ml of above Cu2O Au heterostructures ethanol solution. The mixtures were shaken for several seconds and allowed to standing for 40 minutes. The products were collected by centrifugation at 8000 rpm for 1 minute and washed with ethanol several times. 5. Synthesis of Au-HKUST-1 composite nanocapsules The obtained Cu2O Au-HKUST-1 core-shell heterostructures were dispersed in the mixture of 5 ml ethanol and 50 μl acetic acid. The mixtures were shaken for several seconds and allowed to standing for 12 hours. The products were collected by centrifugation at 6000 rpm for 3 minute and washed with ethanol several times. 6. Synthesis of HKUST-1 crystals HKUST-1 crystals were synthesized following the procedure of Chui et al Catalytic reaction of CO oxidation. Au-HKUST-1 nanocapsules and absolute HKUST-1 crystals were evaluated in a continuous flow system (1% CO and 99% Air) with a flow rate of 25 ml min -1. The reaction with 60 mg catalyst was carried out in a quartz tubular reactor heated by a furnace with temperature controller at temperatures between 60 C and 220 C. The end gas was analyzed by a Shimadzu GC-8A gas chromatograph with a TCD detector after reaction maintained for 10 min at a certain temperature. Prior to the evaluation, both samples were evacuated at 120 C for 8 hours to remove the free molecules in pores of HKUST-1. S-3

4 Figure S1. SEM image of octahedral Cu 2O nanocrystals S-4

5 Figure S2. SEM images of Cu 2O-Au heterostructures prepared using different concentration of HAuCl 4 4H 2O ethanol solution: 0.5 mm (a), 1.0 mm (b), 1.5 mm (c) and 2.0 mm (d). As can be observed in Figure S2 b-d, the size of Au NPs on the surfaces of Cu2O increases with the increasing of the concentration of HAuCl4 ethanol solution. However, when the concentration of HAuCl4 ethanol solution decreases into 0.5 mm, the size of Au NPs become about 10 nanometers (Figure S2a), larger than that when the concentration of HAuCl4 ethanol solution is 1.0 mm (Figure S2b). This phenomenon could be explained by the growth kinetics of Au NPs. As can be observed in Figure S2 b-d, the numbers of Au NPs formed on the surfaces of Cu2O are similar when the concentration of HAuCl4 ethanol solution is above 1.0 mm. However, the number of Au NPs (Figure S2a) is obviously smaller than the other three (Figure S2, b-d), indicating the seeds of Au NPs are rarely formed on the surfaces of Cu2O when the concentration of HAuCl4 ethanol solution is 0.5 mm. The bigger size of Au NPs when the concentration of HAuCl4 ethanol solution is 0.5 mm (Figure S2a) than that when the concentration of HAuCl4 ethanol solution is 1.0 mm (Figure S2b) is probably resulted from that a seed could acquire more Au source when the total seeds number decreases. S-5

6 Figure S3. XRD spectra of standard Au (JCPDS no ), Au-HKUST-1 nanocapsules and simulated HKUST-1, respectively. S-6

7 Figure S4. SEM images of the coordination replication products with using sole ethanol solvent (a, b), mixed solvents with the ratio of DMA to ethanol of 1:3 (c, d) and 1:1 (e, f). solvents ethanol Ethanol/DMA = 3:1 Ethanol/DMA = 1:1 HKUST-1 shell massive mature and uniform immature Scheme S1. Influence of solvents on HKUST-1 shell S-7

8 Figure S5. SEM images of the coordination replication products with using 240 mm of H 3btc ethanol solution (a, b) and at the reaction temperature of 50 o C (c, d). As H3btc ligand is a kind of mild acid, increasing the concentration of H3btc ethanol solution could increase the acidity of the reaction mixture, which accelerates the oxidative dissolution of Cu2O. In addition, the concentration of btc 3- also increases resulting in a high rate of coordination reaction for assembling HKUST-1 crystals. In general, HKUST-1 shells are constituted by block crystals with the appearance of freestanding HKUST-1 crystals (Figure S5a and b). Thicker HKUST-1 shells and freestanding HKUST-1 crystals could be observed when reaction temperature increases into 50 o C (Figure S5c and d), which could be due to that the high reaction temperature increases both the oxidative dissolution rate of Cu2O and coordination rate of Cu 2+ with btc 3- ligands. S-8

9 References 1. Wang, Z.; Lou, X. W. TiO 2 Nanocages: Fast Synthesis, Interior Functionalization and Improved Lithium Storage Properties. Adv. Mater. 2012, 24 (30), Chui, S. S.-Y.; Lo, S. M.-F.; Charmant, J. P. H.; Orpen, A. G.; Williams, I. D. A Chemically Functionalizable Nanoporous Material [Cu 3(TMA) 2(H 2O) 3] n. Science 1999, 283 (5405), S-9