The influence of porosity on nanoparticle formation in hierarchical aluminophosphates

In this work we explore the deposition of gold onto a silicoaluminophosphate, using a variety of known nanoparticle deposition techniques. By comparing the gold particles deposited on a traditional microporous aluminophosphate, with an analogous hierarchical species, containing both micropores and mesopores, we explore the influence of this dual porosity on nanoparticle deposition. We show that the presence of mesopores has limited influence on the nanoparticle properties, but allows the system to maintain porosity after nanoparticle deposition. This will aid diffusion of reagents through the system, allowing continued access to the active sites in hierarchical systems, which offers significant potential in catalytic oxidation/reduction reactions.


SAPO-5 synthesis
As per our previous work [1], for the synthesis of MP-SAPO-5, pseudo boehmite (3.0 g), H3PO4 (5.8 g, 85 wt % in water) and deionised water (22.5 mL) were added to a small teflon beaker and left to stir for 4 h. Triethylamine (TEA) (5.0 g) and colloidal silica gel (1.5 g) were added dropwise sequentially to the gel and stirred for 2 h. The gel (Table S1) was then transferred into PTFE-lined autoclaves and heated at 200 °C for 24 h. For HP-SAPO-5, a similar experimental procedure was followed, except 42 wt % DMOD in methanol (3.4 mL) was added to the reaction mixture along with the TEA and colloidal silica gel (Table S1). Samples were then washed with 1 L of deionised water and dried at 70 °C overnight. They were then calcined at 600 °C in a flow of air at 2.5 °C/min for 16 h.

Incipient wetness deposition (IW)
The support (0.5 g) was added to a round-bottom flask and stirred while 0.5 mL of a

Wetness impregnation deposition (WI)
The support (0.5 g) was added to a round-bottom flask and stirred while 0.5 mL of a

Powder XRD (XRD)
Powder XRD patterns were collected on a Bruker AXS D2 Phaser with Cu Kα radiation.

Nitrogen physisorption
A Micromeritics TriStar II 3020 surface area analyser was used for nitrogen physisorption at 77 K. Surfaces areas were calculated using the BET model [2] and the Barrett-Joyner-Halenda (BJH) method [3] was used to determine pore sizes and volumes.

Scanning electron microscopy (SEM)
SEM images were performed using a JSM-5900 LV SEM. The samples were sputtered with gold prior to the measurements.

Induced coupled plasma-mass spectrometry (ICP-MS)
10 mg of samples was first digested in 1 mL of concentrated HNO3, 1 mL of concentrated HCl and 0.75 mL of concentrated HF. The samples were heated overnight at 120 °C to ensure complete digestion occurred. Samples were then diluted into 60 mL of deionised water and then diluted 1:100 into 3% HNO3 in deionised water.
These samples were then measured on a high-resolution ICP-MS

UV-vis spectroscopy
UV/Vis spectra were obtained using a Perkin Elmer Lambda 35 spectrometer in diffuse reflectance mode, with appropriate background subtraction.

X-ray photoelectron spectroscopy (XPS)
XPS analysis was performed using a Thermo Scientific K-Alpha+ / NEXSA instrument         Plots are stacked in increments of 0.05 cm 3 /g for clarity. Plots are stacked in increments of 0.05 cm 3 /g for clarity. Probing the gold species on deposited systems with UV-vis spectroscopy Figure

Toluene oxidation
Toluene (16.5 mmol, 1.52 g), 70% TBHP in water (16.5 mmol, 2.28 mL) and bis(2-methoxyethyl) ether (diglyme) (1.9 mmol, 0.28 mL) were all added to a roundbottom flask (10 mL), which was then sealed and stirred at 80 °C in a pre-heated oil bath. 50 mg of catalyst was added to the mixture and left to stir for 24 h. The samples were analysed using a Perkin Elmer 3400CX gas chromatogram with flame ionisation detector (FID). Products were identified against authenticated standards, and quantified by via calibration of measured response factors against the diglyme internal standard.