SUPPLEMENTARY INFORMATION - media.nature.com · 1 Spatially orthogonal chemical functionalization of a hierarchical pore network for catalytic cascade reactions Christopher M.A. Parlett

1

Spatially orthogonal chemical functionalization of a hierarchical pore network for catalytic

cascade reactions

Christopher M.A. Parlett1, Mark A. Isaacs1, Simon K. Beaumont2, Laura M. Bingham2, Nicole S. Hondow3,

Karen Wilson1 & Adam F. Lee1*

1European Bioenergy Research Institute, Aston University, Birmingham B4 7ET, UK 2Department of Chemistry, University of Durham, Durham DH1 3LE, UK 3Institute for Materials Research, University of Leeds, Leeds LS2 9JT, UK

Material synthesis

Supplementary Figure 1| Polystyrene colloidal nanosphere hard template. (left) SEM micrographs of centrifuged array of PS colloidal nanospheres, and (right) dynamic light scattering particle size distribution.

0

5

10

15

20

25

30

Cou

nts

Polystyrene particle size / nm

SUPPLEMENTARY INFORMATIONDOI: 10.1038/NMAT4478

NATURE MATERIALS | www.nature.com/naturematerials 1

© 2015 Macmillan Publishers Limited. All rights reserved

http://dx.doi.org/10.1038/nmat4478

2

Supplementary Figure 2| Selective removal of polystyrene macropore template. (top) N2 adsorption-

desorption isotherms, and (bottom) macropore surface area of as-synthesised and sub-ambient, toluene-

extracted macroporous silica as a function of extraction cycle. Negligible mesoporosity was observed in all

cases. Five extraction cycles were employed for all macroporous materials functionalised in this work.

0

5

10

15

20

25

0 1 2 3 4 5

Ma

cro

po

re s

urf

ace

are

a / m

2.g

-1

Number of toluene extractions

0

20

40

60

80

100

120

140

0 0.2 0.4 0.6 0.8 1

N2 v

olu

me

/ c

m3.g

-1

Relative pressure / P/P0

Adsorption

Desorption

As-synthesised

Extraction cycle:

4

3

2

1

5


3

Supplementary Figure 3| Hydrophobisation of macroporous silica by triethoxyoctylsilane and mesopore

template retention. (top) N2 adsorption-desorption isotherms, and (top inset) BJH pore size distribution of

macroporous silica after octyl functionalisation; lack of mesoporosity confirms retention of P123 template

during hydrophobisation process. (bottom) Water contact angle analysis of macroporous silica (left) before

and (right) after octyl functionalisation.

0

5

10

15

20

25

30

35

40

45

50

0.0 0.2 0.4 0.6 0.8 1.0

N2 v

olu

me

/

cm

3.g

-1

Relative pressure / P/Po

Adsorption

Desorption

Surface area = 19 m2

.g-1

Macroporous silica

Before octyl-

grafting

Macroporous silica

After octyl-

grafting

Fully wetted

137 °

Strongly hydrophobic

0.0

0.5

1.0

2 4 6 8 10

dV

(lo

gd

) /

a.u

.

Pore diameter / nm


4

Supplementary Figure 4| Removal of P123 mesopore soft template and resulting ordered mesoporosity.

(a) Thermogravimetric profiles during temperature-programmed oxidation of octyl-functionalised

macroporous silica under flowing 80:20 v/v N2/O2 (20 cm3.min

-1 and 10 °C.min

-1 ramp rate) before and after

extraction of P123 mesopore template by methanol reflux. Decrease in the mass of combustible matter and

absence of characteristic P123 exotherm after methanol reflux demonstrates successful mesopore template

extraction. (b, main) N2 adsorption-desorption isotherms, and (b, inset) BJH pore size distribution of

methanol-extracted, octyl-functionalised macroporous silica, confirming removal of P123 mesopore template,

and (c) low angle XRD evidencing p6mm ordered mesophase characteristic of SBA-15.

50

100

150

200

250

300

0.0 0.5 1.0

N2 v

olu

me

/

cm

3.g

-1

Relative pressure / P/P0

Adsorption

Desorption

0 1 2 3 4 5 6

Inte

nsity / a

.u.

2 / °

-2

0

2

4

6

8

10

12

14

16

18

0

10

20

30

40

50

60

70

80

90

100

0 100 200 300 400 500 600

Hea

t flow

/ mV

Ma

ss /

%

Temperature / ° C

Octyl-functionalised Post P123 extraction

P12

3 c

om

bustion

Surface area = 300 m2

.g-1

Mesopore diameter = 3.5 nm Mesopore range = 2.5 -3.75 nm

0

1

2

3

2 4 6 8 10

dV

(lo

gd

) /

a.u

.

Diameter / nm

(100)

(110) (200)

a

b c


5

Supplementary Figure 5| Importance of macropore hydrophobisation. (a, c, e) HRTEM bright-field and

(b, d, f) HAADF-STEM micrographs of a hierarchical macroporous-mesoporous SBA-15 functionalised with

Pt nanoparticles, without octyl pre-functionalisation of macropores. Pt nanoparticles are randomly distributed

throughout the entire bimodal pore network, and (g) exhibit a broad particle size distribution with a significant

fraction of particles >3.5 nm, i.e. larger than the mesopores, which must be present within the macropores.

This highlights the importance of octyl pre-functionalization of the macropores in controlling the size and

location of Pt within the framework.

a

b

c

d

e

Macropore surface

Mespore channels

Macropore

f

Mespore

g

0

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20

30

40

50

60

70

80

90

100

0

5

10

15

20

25

0.5

1 1.5

2 2.5

3 3.5

4 4.5

5 6 7 8

Cum

ula

tive

/ %

Fre

qu

en

cy /

%

Pt particle size / nm

Frequency

Cumulative


6

Supplementary Figure 6| Uniformity of colloidal Pd nanoparticles. (left) TEM micrograph and particle

size distribution from six similar images which exhibited minimal deviation; mean particle diameter = 5.6

0.8 nm, and (right) HRTEM micrograph showing Pd metallic character (fcc lattice).


7

Supplementary Figure 7| Independent functionalisation of either macropores or mesopores. (a) SEM

and (b) DF-STEM micrographs of a hierarchical macroporous-mesoporous SBA-15 functionalised with

colloidal Pd nanoparticles exclusively within macropores; all particles are common to both images, i.e. no

particles reside within the mesopore framework. (c,e) SEM and (d,f) DF-STEM and (g) backscattered SEM

micrographs of a hierarchical macroporous-mesoporous SBA-15 functionalised with Pt nanoparticles

exclusively within mesopores channels; no particles are visible either within, or on the surface, of macropores.

c

d

e

f

gMacropore surfaceMacropore network

Mespore channels

+ Pt nanoparticles

Pt nanoparticles

Macropore network

a b


8

Supplementary Fig. 8| Spatially orthogonal co-functionalisation of macropores and mesopores (a, d, g)

SEM and (b, e, h) DF-STEM and (c, f, i) backscattered SEM micrographs of a hierarchical macroporous-

mesoporous SBA-15 functionalised with Pt nanoparticles exclusively within mesopore channels and Pd

nanoparticles exclusively within macropores. High contrast exemplar features that are unique to mesopores

are ringed in blue; low contrast features visible on the macropore surface are ringed in grey.

a

d

b

e

c

f

g h i


9

Supplementary Figure 9| Incorporation of larger metallic Pd nanoparticles. Powder XRD patterns for a

hierarchical macroporous-mesoporous SBA-15 functionalised with either Pd nanoparticles exclusively within

the macropores, Pt nanoparticles exclusively within the mesopores, or Pd within the macropores and Pt within

the mesopores. Only reflections characteristic of fcc Pd crystallites of ~5 nm volume averaged diameter are

apparent; the absence of reflections attributable to any Pt phase is consistent with sub-3 nm particles below the

XRD sensitivity limit.

10 20 30 40 50 60 70 80

2 / °

Pd Macro-Pt Meso

Pd Macro

Pt Meso

fcc (111) 5 nm Pd NPs


10

Supplementary Table 1| Localisation of Pd and Pt within respective macropore and mesopores.

Porosimetry employing N2 physisorption identified minimal change in the average textural properties of the

(fully detemplated) hydrophobised hierarchical macroporous-mesoporous SBA-15 following the introduction

of 5 nm colloidal Pd nanoparticles, consistent with their selective incorporation within macropores. In

contrast, wet impregnation of the (detemplated) hydrophobised hierarchical macroporous-mesoporous SBA-

15 resulted in significant loss of BET and mesopore areas and mesopore volume, consistent with Pt

incorporation within mesopores. Textural properties of hierarchical macroporous-mesoporous SBA-15

functionalised with both Pd and Pt via our new synthetic route were akin to those of the Pt mesopore only

material.

Material BET m2.g-1

BET

area

/ %

DFT mesopore

volume

/ cm3

Mesopore

volume

/ %

DFT mesopore

area

/ m2.g-1

Mesopore

area

/ %

BJH

mesopore

diameter

/ nm

Hydrophobised

hierarchical SBA-15 297

0.33

235

3.6

Pd (macropores only)

hierarchical SBA-15 282 -5 0.34 6 246 5 3.6

Pt (mesopores only)

hierarchical SBA-15 216 -27 0.26 -21 170 -28 3.6

Pd macroporous-Pt

mesoporous SBA-15 191 -36 0.24 -26 162 -31 3.6

Supplementary Figure 10| Illustration of spatial control for cascade reactions. Spatially orthogonal

functionalization of hierarchical pore network affords precise control over reaction sequence in catalytic

cascades: Substrate entering macropores first encounters active species A (Pd NPs shown in blue) to form

Product 1, which subsequently diffuses into interconnected mesopores to undergo reaction over active

species B (Pt NPs shown in grey) to form Product 2. Undesired reaction of Substrate with active species B is

prohibited by the hierarchical nature of mesopore accessibility via macropores.

1

2


11

Cinnamyl alcohol aerobic selective oxidation

Comparison of spatially orthogonal bimetallic catalyst with monometallic counterparts

Quantitative comparison of the performance of our spatially orthogonal bimetallic catalyst with relevant

monometallic and bimetallic counterparts was undertaken in order to evaluate the impact of spatial

localisation of Pd and Pt upon selectivity to the desired cinnamaldehyde and cinnamic acid products. Since Pd

is selective to cinnamyl alcohol oxidation to cinnamaldehyde (but unreactive towards cinnamaldehyde),

whereas Pt favours cinnamyl alcohol hydrogenation and decarbonylation (but selective for cinnamaldeyde

oxidation to cinnamic acid), ones anticipates that the rate of cinnamyl alcohol diffusion from macropores (Pd)

to mesopores (Pt) is pivotal in determining product selectivity.

Defining selectivity = [Product]/[Total concentration of all products], then for the monometallic counterparts:

1 wt% Pd (macropores only) hierarchical SBA-15 = 74 % cinnamaldehyde selectivity

1 wt% Pt (mesopores only) hierarchical SBA-15 = 8 % cinnamaldehyde selectivity

If Pd and Pt were co-localised throughout both pore networks, then the predicted cinnamaldehyde selectivity

is given by the mean of the individual selectivities above, weighted by their respective TOFs for alcohol selox

(7762 and 4898 h-1

per surface PdO or PtO2 site, these being the respective active species) and atom% of each

metal. Since the composition of our hierarchical 1 wt% Pd macroporous-1wt% Pt mesoporous SBA-15

catalyst is 65:35 atom% Pd:Pt, then:

Predicted cinnamaldehyde selectivity = (0.65 𝑥 𝑤𝑒𝑖𝑔ℎ𝑡𝑒𝑑 𝑇𝑂𝐹𝑃𝑑

𝐶𝑖𝑛𝑛𝑂𝐻𝑥 74)

0.65 +

(0.35 𝑥 𝑤𝑒𝑖𝑔ℎ𝑡𝑒𝑑 𝑇𝑂𝐹𝑃𝑡𝐶𝑖𝑛𝑛𝑂𝐻𝑥 8)

0.35 = 49 %

Supplementary Equation 1

where the weighted TOF = TOFxCinnOH

/ (TOFPdCinnOH

+ TOFPtCinnOH

).

This predicted cinnamaldehyde selectivity of only 49 % for co-located Pd and Pt contrasts with the 71 %

observed for our spatially orthogonal catalyst, the latter being very close to the 74 % observed for cinnamyl

alcohol selox over Pd alone in the macropores. In other words, the overall selectivity to cinnamaldehyde is

very close to that expected if cinnamyl alcohol reacted solely over Pd, which is only possible if the rate of

cinnamyl alcohol selox over Pd exceeds the rate of CinnOH diffusion from macroporesmesopores (where

Pt is located).


12

Cinnamyl alcohol oxidation reaction profiles

Supplementary Figure 11| Selective aerobic oxidation of cinnamyl alcohol. Conversion reaction profiles

for cinnamyl alcohol selox under identical conditions over our spatially orthogonal Pd macroporous-Pt

mesoporous SBA-15 catalyst, and a range of monometallic and bimetallic controls are shown, highlighting the

benefits of localisation the two metal active sites within different pore networks. Reaction conditions: 150 C,

5 bar O2, 12.5 mg catalyst, 4.1 mmol cinnamyl alcohol in toluene solvent.

a

d


13

Supplementary Figure 12| Selective aerobic oxidation of cinnamyl alcohol. Product selectivity profiles for

cinnamyl alcohol selox under identical conditions over our spatially orthogonal Pd macroporous-Pt

mesoporous SBA-15 catalyst compared with Pt and Pt either uniformly co-located throughout the entire pore

network, or co-located within macropores, highlighting the benefits of localisation the two metal active sites

within different pore networks. Reaction conditions: 150 C, 5 bar O2, 12.5 mg catalyst, 4.1 mmol cinnamyl

alcohol in toluene solvent.

Spatially orthogonal PdPt

0

20

40

60

80

100

0 1 2 3 4 5 6

Sele

ctivity / %

Reaction time / h

Cin=O

ethylbenzene

Trans-β-methylstyrene

0

2

4

0 1 2 3 4 5 6

Sele

ctivity / %

Reaction time / h

Cin-OOHStyreneHydroCin=OHydroCin-OHHydroCin-OOH

0

20

40

60

80

100

0 1 2 3 4 5 6

Sele

ctivity / %

Reaction time / h

Cin=O

ethylbenzene

0

20

0 1 2 3 4 5 6

Sele

ctivity / %

Reaction time / h

Cin-OOH

StyreneHydroCin=OHydroCin-OH

HydroCin-OOHPdPt throughout hierarchy

Pd and Pt in macropores

0

20

40

60

80

100

0 1 2 3 4 5 6

Sele

ctivity / %

Reaction time / h

Cin=O

ethylbenzene


0

10

20

0 1 2 3 4 5 6

Sele

ctivity / %

Reaction time / h


Key: Cinnamaldehyde Cin=O

Cinnamic acid Cinn-OOH

Hydrocinnamaldehyde HydroCin=O

Hydrocinnamyl alcohol HydroCin-OH

Hydrocinnamic acid HydroCin-OOH


14

Supplementary Figure 13| Selective aerobic oxidation of cinnamyl alcohol. Product selectivity reaction

profiles for cinnamyl alcohol selox under identical conditions over macroporous-mesoporous SBA-15 with Pd

and Pt co-located within mesopores, Pd uniformly distributed throughout the entire pore network with Pt only

within the mesopores, or Pt uniformly distributed throughout the entire pore network with Pd only within the

macropores which show no evidence for synergy except in the case where Pt is spatially confined to

mesopores with Pd throughout (this being the closest analogue to our spatially orthogonal catalyst). Reaction

conditions: 150 C, 5 bar O2, 12.5 mg catalyst, 4.1 mmol cinnamyl alcohol in toluene solvent.

PdPt in mesopores

0

20

40

60

80

100

0 1 2 3 4 5 6

Se

lectivity / %

Reaction time / h

Cin=O

ethylbenzene


0

10

20

30

0 1 2 3 4 5 6

Sele

ctivity / %

Reaction time / h


Pt meso and Pd throughout

0

20

40

60

80

100

0 1 2 3 4 5 6

Se

lectivity / %

Reaction time / h

Cin=O

ethylbenzene


0

2

4

6

0 1 2 3 4 5 6

Sele

ctivity / %

Reaction time / h


Pt all over and Pd macro

0

20

40

60

80

100

0 1 2 3 4 5 6

Se

lectivity / %

Reaction time / h

Cin=OethylbenzeneTrans-β-methylstyrene

0

5

10

0 1 2 3 4 5 6

Sele

ctivity / %

Reaction time / h








15

Supplementary Figure 14| Selective aerobic oxidation of cinnamyl alcohol. Product selectivity reaction

profiles for cinnamyl alcohol selox under identical conditions over macroporous-mesoporous SBA-15 with

only Pd nanoparticles localised within macropores, only Pt nanoparticles localised within mesopores, or a

physical mixture of the two catalysts which shows no evidence of synergy between the two physically discrete

catalysts. Reaction conditions: 150 C, 5 bar O2, 12.5 mg catalyst, 4.1 mmol cinnamyl alcohol in toluene

solvent.

0

20

40

60

80

100

0 1 2 3 4 5 6

Sele

ctivity / %

Reaction time / h

Cin=O

ethylbenzene


0

1

2

3

4

0 1 2 3 4 5 6

Sele

ctivity / %

Reaction time / h


Pd macropore only

0

20

40

60

80

100

0 1 2 3 4 5 6

Se

lectivity / %

Reaction tIme / h

Cin=O

ethylbenzene


0

10

20

30

0 1 2 3 4 5 6

Se

lectivity / %

Reaction time / h


Pt mesopore only

Mix [Pd macro]+[Pt meso]

0

20

40

60

80

100

0 1 2 3 4 5 6

Se

lectivity / %

Reaction time / h

Cin=OethylbenzeneTrans-β-methylstyrene

0

10

20

0 1 2 3 4 5 6

Se

lectivity / %

Reaction time / h








16

Cinnamic acid spiking

The importance of spatially separating the selective oxidation step over Pd which produces cinnamaldehyde

from that over Pt which produces cinnamic acid, and controlling the sequence of these two reactions, such that

cinnamic acid is only formed after cinnamyl alcohol has already undergone oxidation to cinnamaldehyde, was

highlighted through a spiking test in which 0.1 mmol cinnamic acid was added at the start of a reaction (see

below). Introduction of cinnamic acid direct to the solution mixture enables its competitive adsorption with

cinnamyl alcohol over Pd within the macropores, enhancing the relative rate of cinnamyl alcohol

decarbonylation over Pd, such that the total 6 h selectivity to decarbonylation products increased from 21 % to

46 %, at the expense of selective oxidation to cinnamaldehyde. In contrast, cinnamic acid spiking had little

impact upon the rate of hydrogenation, with total 6 h selectivity to hydrogenation products unchanged at

around 6 %.

Supplementary Figure 15| Cinnamic acid spiking of cinnamyl alcohol selox. A cinnamic acid spiking

experiment highlights the benefits of spatially separating individual oxidation steps; 0.1 mmol cinnamic acid

was directly introduced to the solution mixture at the start of the reaction, enabling its competitive adsorption

with cinnamyl alcohol over Pd within the macropores. Cinnamic acid addition promotes undesired cinnamyl

alcohol decarbonylation over Pd at the expense of its selective oxidation to cinnamaldehyde.

0

10

20

30

40

50

Totaldecarbonylation

Totalhydrogenation

4.2 mmol CinnOH

4.2 mmol CinnOH +0.1 mmol CinnOOH


17

Supplementary Table 2| Benchmarking against state-of-the-art PGM selox catalysts. Our spatially

orthogonal Pd macroporous-Pt mesoporous SBA-15 catalyst affords superior Turnover Frequencies for

cinnamyl alcohol oxidation to any published materials under comparable conditions. It also exhibits good

selectivity to cinnamaldehyde, superior to any comparable high activity system (those reporting selectivities

>90 % only offer TOFs <100 h-1

), and crucially, is the only heterogeneous catalyst to our knowledge able to

produce quantifiable yields of cinnamic acid in a one-pot oxidation of cinnamyl alcohol.

Catalyst TOF

CinnOH

conversion

/ h-1

CinnCHO

selectivity

TOF

Cinnamic

acid

production

/ h-1

Substrate:catalyst

molar ratio

Base Reaction

conditions

Reference

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meso SBA-15

8500

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16

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Pd@CeO2 83 99 0 125 No 80 C, 1 bar ChemCatChem

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Pd/HAP 455 95 0 500 HAP 90 C, 1bar J. Am. Chem.

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Cu-

nanoparticles on cellulose

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activated carbon

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SUPPLEMENTARY INFORMATION - media.nature.com · 1 Spatially orthogonal chemical functionalization of a hierarchical pore network for catalytic cascade reactions Christopher M.A. Parlett