Supporting Information

Transcription

1 Supporting Information Wiley-VCH Weinheim, Germany

2 Zn-MCM-48 Supporting Hydrated Dibromodioxomolybdenum(Ⅵ) for Facile Conversion of Methane to Methyl Oxygenated Products Fengbo Li, Guoqing Yuan* [ ] Prof. G.Yuan, F. Li Beijing National Laboratory for Molecular Sciences Laboratory of New Materials, Institute of Chemistry, Chinese Academy of Sciences Beijing, , China Fax: (+) yuangq@iccas.ac.cn

3 Figure S1. a) Powder XRD patterns of MCM-48 (1) and Zn-MCM-48 (2-6) materials. b) N 2 sorption isothermals of MCM-48 (1) and Zn-MCM-48 (2-6) materials. c) Powder XRD patterns of the samples loaded with MoO 2 Br 2 (H 2 O) 2. The Si/Zn ratio in the incipient gel: 2) 60, 3) 40, 4) 20, 5) 10, and 6) 5.

4 Table S1. Textural properties of Zn-MCM-48 materials Sample Si/Zn [a] 2θ [f] MCM ( o ) 2.50(2.36) 2.38(2.32) 2.32(2.28) 2.36(2.32) d 211 spacing (Å) [f] 35.3(37.4) 37.1(38.1) 38.0(38.7) 37.4(38.0) [b], [f] Lattice parameter (Å)a o 86.5(91.6) 90.9(93.3) 93.1(94.8) 91.6(93.1) Surface area (m 2 /g) Pore volume (ml/g) [c] Pore size (Å) [d] Wall thickness [a] The mole ratio of Si to Zn in the incipient gel. [b]the lattice parameter is calculated by the formula a o =d [c]pore volume is mesopore volume. [d] Pore size is calculated by the formula, pore size =4V meso /S, where V meso is the mesopore volume and S is the surface area. [e] Wall thickness is calculated from the equation, wall thickness =a o / pore size/2. [f] Values in the parenthesis are data for the supports loaded with hydrated dibromodioxomolybdenum. (Å) [e] Figure S2. Mo XPS peaks of MoO 2 Br 2 (H 2 O) 2 core. 1) MoO 2 Br 2 (H 2 O) 2 diglyme, 2) MoO 2 Br 2 (H 2 O) 2 /-20, 3) MoO 2 Br 2 (H 2 O) 2 /-20 exposed to air for 24 h, and 4) MoO 2 Br 2 (H 2 O) 2 /-20 heated in air at 100. Zn-MCM-48 was synthesized from the incipient gel with the molar ratio SiO 2 : xzn(oh) 2 : 0.28CTAOH: 42H 2 O (where x = 0.017, 0.025, 0.05, 0.1, 0.2; silica source is TEOS). To the best of our knowledge, the incorporation of Zn to mesoporous silica sieves via direct mixed-gel synthesis is first attempted in this work and the existence of Zn in the sieves is a key parameter affecting the catalytic stability. The powder XRD patterns (Figure S1a) of the parent calcined MCM-48 and Zn-MCM-48 can be indexed on a cubic unite cell (using the strongest (211) diffraction peaks, a o = Å). For MCM-48, -60, and 40, with increasing Zn contents, the basal diffraction peak (211) shifts to lower 2θ values and the basal spacing increases. Such increase suggests the expansion of the lattice. The lattice parameter (a o ), which is the distance between two nearest pore centers calculated on the cubic unite cell (a o =d 211 6), increases as shown in Table S1. For -20, 10 and 5, with increasing Zn contents, 2θ values of the peak (211) keep constant, but their intensities are reduced sharply. This suggests diminishing of structural ordering. Figure S1c shows the powder XRD patterns of the supports loaded with MoO 2 Br 2 (H 2 O) 2. The basal (211) diffraction peaks are clearly observed. This indicates that the structure of Zn-silica mesoporous sieves remains intact through the supporting

5 procedure. The incorporation of MoO 2 Br 2 (H 2 O) 2 cause sharp decrease of the (211) peak intensities. This may be due mainly to contrast matching between the silicate framework and the species located inside the pores of mesoporous sieves. The (211) peaks shift to lower 2θ values indicates that the cubic unite cell expands (the lattice parameters increase) (Table S1) with the impregnation of MoO 2 Br 2 (H 2 O) 2. The N 2 sorption isotherm of MCM-48 (Figure S1b-1) is type Ⅳ isotherm with a typical capillary condensation in the relative pressure from 0.2 to 0.4, which indicate that the sample has good mesopore structural ordering and narrow pore size distribution. For -60, 40, and 20, the N 2 sorption isotherms bear an analogy to type Ⅱ isotherm, which have relatively poorly defined capillary condensation step and show unsaturated sorption at the high relative pressure. This indicates the broadening of the pore size distribution. However, they exhibit marked increasing of the surface area, which is resulted from the Zn incorporation. The N 2 sorption isotherms of -10 and 5 exhibit much similarity to type Ⅳ isotherm and the capillary condensation steps in the relative pressure from 0.2 to 0.4 are poorly defined. Their surface areas decrease markedly and pore size shrinks with the increasing of Zn contents (Table S1). MoO 2 Br 2 (H 2 O) 2 occurs in solutions of alkali molybdates in concentrated hydrobromic acid and can be extracted by diethyl ether. Yellow crystal of MoO 2 Br 2 (H 2 O) 2 2(Et) 2 O can be obtained by cool the MoO 2 Br 2 (H 2 O) 2 diethyl ether solution at 5, which is the precursor for the preparation of Zn-MCM-48 supporting MoO 2 Br 2 (H 2 O) 2. MoO 2 Br 2 (H 2 O) 2 stabilized by the simple diglyme, which is sufficiently stable to be operated in air at room temperature, is used as the reference to prove its existence inside the pores of the mesoporous sieves. The molybdenum XPS biding energy of MoO 2 Br 2 (H 2 O) 2 diglyme is ev (3d 5/2 ) and the supported MoO 2 Br 2 (H 2 O) 2 shows Mo 3d 5/2 at ev (Figure S2). These illustrate that the change of stabilizers has little influence on the chemical state of MoO 2 Br 2 (H 2 O) 2 core. But the stabilizers determine the stability of the resulting adducts. MoO 2 Br 2 (H 2 O) 2 supported by Zn-MCM-48 show lower stability than MoO 2 Br 2 (H 2 O) 2 diglyme. When exposed to air at room temperature for one day, it is observed that the light yellow MoO 2 Br 2 (H 2 O) 2 /-20 turns to blue and releases volatile Br 2 gradually. This indicates that the supported MoO 2 Br 2 (H 2 O) 2 decomposes to Br 2 and molybdenum blue, which shows Mo 3d 5/2 biding energy at 231.7eV (Figure S2). When heated in air at 100, the supported MoO 2 Br 2 (H 2 O) 2 releases a great amount of volatile Br 2 and the molybdenum blue is oxidized to yellow MoO 3 by O 2 (Mo 3d 5/2 biding energy: 232.6, Figure S2).