Spirobifluorene-based Porous Organic Polymers as Efficient Porous Supports for Pd and Pt for Selective Hydrogenation

Article abstract of DOI:10.1002/cctc.201801247

Spirobifluorene-based porous organic polymers (POP) were synthesized following two different protocols; the acetylenic coupling reaction conditions and the Sonogashira cross-coupling reaction. These were utilized as support for the hydrogenation of a series of species containing unsaturated C=C and C=O bonds (4-nitrostyrene, 4-bromobenzophenone, acetophenone, 7-nitro-1-tetralone and 1,2-naphtoquinone confirmed their efficiency). POP1 prepared via a copper-catalysis protocol was completely inactive, while POP2-4 containing residual Pd exhibited different activities in accordance to the accessibility of the substrates to the metal. Further deposition of 0.5 wt% Pd led to active and stable catalysts. They were easily separated by filtration, and after re-dispersion, afforded the same performances for ten successive cycles. This study also evidenced the specific role of the support in these reactions by comparing the behavior of Pd/POP with that of a Pd/C catalyst with the same loading of palladium. The deposition of Pt on these supports led to sub-nanometric particles and, in accordance, to a different catalytic behavior reflected merely by differences in the selectivity.

Full text of DOI:10.1002/cctc.201801247

Accepted Article
Title: Spirobifluorene-based porous organic polymers as efficient
porous support for Pd and Pt for the selective hydrogenations
Authors: Mihaela Trandafir, Lidia Pop, Niculina Daniela Hadade, Ioana
Hristea, Cristian Mihail Teodorescu, Frank Krumeich, Jeroen
Anton van Bokhoven, Ion Grosu, and Vasile I. Parvulescu
This manuscript has been accepted after peer review and appears as an
Accepted Article online prior to editing, proofing, and formal publication
of the final Version of Record (VoR). This work is currently citable by
using the Digital Object Identifier (DOI) given below. The VoR will be
published online in Early View as soon as possible and may be different
to this Accepted Article as a result of editing. Readers should obtain
the VoR from the journal website shown below when it is published
to ensure accuracy of information. The authors are responsible for the
content of this Accepted Article.
To be cited as: ChemCatChem 10.1002/cctc.201801247
Link to VoR: http://dx.doi.org/10.1002/cctc.201801247
A Journal of
www.chemcatchem.org

10.1002/cctc.201801247
ChemCatChem
Spirobifluorene-based porous organic polymers as efficient porous support for Pd
and Pt for the selective hydrogenations
Mihaela Trandafir[a]#, Lidia Pop[b] #, Niculina D. Hӑdade[b], Ioana Hristea[c], Cristian Mihail
Teodorescu[c], Frank Krumeich[d], J.A. van Bokhoven[d] *, Ion Grosu[b]*and Vasile I.
Parvulescu[a]*
[a]University of Bucharest, Department of Organic Chemistry, Biochemistry and Catalysis, 4-12
Regina
Elisabeta
Blvd.,
030016
Bucharest,
Romania;
E-mail:
vasile.parvulescu@chimie.unibuc.ro
[b]Babes-Bolyai University, Faculty of Chemistry and Chemical Engineering, Department of
Chemistry, Cluj-Napoca, 11 Arany Janos str., 400028, Cluj-Napoca, Romania, e-mail:
igrosu@chem.ubbcluj.ro
[c]National Institute of Materials Physics, Department of Surfaces and Interfaces, Atomistilor 405
A, 077125 Magurele-Ilfov, Romania, e-mail: teodorescu@infim.ro
[d]
Institute for Chemical and Bioengineering, ETH Zurich, HCI D 130 Vladimir-PrelogWeg 1,
8093 Zurich, Switzerland, Paul Scherrer Institure, 5323 Villigen, Switzerland, e-mail:
jeroen.vanbokhoven@chem.ethz.ch
#- participated equally
Spirobifluorene-based porous organic polymers (POP) were synthesized following two different
protocols; the acetylenic coupling reaction conditions and the Sonogashira cross-coupling
reaction. These were utilized as support for the hydrogenation of a series of species containing
unsaturated C=C and C=O bonds (4-nitrostyrene, 4-bromobenzophenone, acetophenone, 7-nitro-
1-tetralone and 1,2-naphtoquinone confirmed their efficiency). POP1 prepared via a copper-
catalysis protocol was completely inactive, while POP2-4 containing residual Pd exhibited
different activities in accordance to the accessibility of the substrates to the metal. Further
deposition of 0.5wt% Pd led to active and stable catalysts. They were easily separated by
filtration, and after re-dispersion, afforded the same performances for ten successive cycles. This
study also evidenced the specific role of the support in these reactions by comparing the
behaviour of Pd/POP with that of a Pd/C catalyst with the same loading of palladium. The
deposition of Pt on these supports led to sub-nanometric particles and, in accordance, to a
different catalytic behaviour reflected merely by differences in the selectivity.
This article is protected by copyright. All rights reserved.

10.1002/cctc.201801247
ChemCatChem
Introduction
The chemoselective reduction of organic compounds is an important step in the synthesis of
various valuable compounds for both industrial and fine chemical processes.[1] Among others,
the selective hydrogenation of the carbonyl compounds to the corresponding alcohols may
produce platform molecules for the synthesis of different fine-chemicals.[2] Literature has largely
investigated this reaction taking as substrates both aldehydes and ketones and molecular
hydrogen or isopropanol as the hydrogen source.[3]
Hydrogenation by molecular hydrogen requires an adequate catalyst able to dissociate the
hydrogen and to activate the substrate. Generally, the catalysts used for the reduction reactions
contain transition metals (Fe, Co, Ni, Cu, Ru, Rh, Pd, Ir, Pt, Au).[4, 5] Further heterogenization of
these catalysts by their deposition onto solid supports, especially as metal nanoparticles (NPs),
provides specific advantages as high turnover number (TON), good selectivity and good
recyclability.[6] An adequate support eliminates some drawbacks, as the agglomeration during
their synthesis or reaction. The use of porous supports with a high surface area and controlled
pore size distribution allows an increased productivity and shape control selectivity.[7]
Metal oxide catalysts can act as appropriate supports, some of them being also active for
hydrogen transfer reactions.[8] They afford large surface areas, have a very good dispersion of the
catalytic active phase and may influence the oxidation state of the metal and ensure hydrogen to
spillover.[9] Materials such as mesoporous activated carbon, graphitic carbon nitride, carbon
nanotubes and graphenes are also suitable supports for the metal catalysts in the hydrogenation
reactions.[10] These materials have the advantage of sustainability, as these can be produced from
renewable resources.
Among these, porous organic polymers (POPs) gained a significant interest, the very large
surface areas and the good thermal stability recommending them as adsorbents and catalytic
supports.[11] The intrinsic properties of these new materials are the effect of the covalent organic
bonds participating in their construction,[12] while the catalytic ones are afforded by isolated
ions,[13] entrapped metal-complexes or nanoparticles.[14] The porous structure is able to stabilize
the metal NPs, making these highly active and reusable for heterogeneous catalysis.[15]. In this
context POP supported palladium catalysts showed efficiency for controlling the selectivity in
This article is protected by copyright. All rights reserved.

10.1002/cctc.201801247
ChemCatChem
specific reactions as Suzuki–Miyaura, Heck, and Sonogashira cross-couplings [16], or the
chemoselective decarbonylation of aldehydes[17]
.
In comparison to the coordination-bonded MOFs, POPs are generally less susceptible to
chemical degradation and water. This ensures the intactness of the catalysts during operation.
Both the structure and texture of these porous materials can be intimately tailored by the
selection of the building units.[18] In this way, these materials may enhance the properties of the
carbonaceous supports.[19] They can be constructed through covalent bonds, such as C–C ones[20]
from a variety of building blocks, including tetrahedral units starting from derivatives of
tetraphenyl-methane,[21-24] -silane,[23-25] -adamantane[21, 24, 26, 27] or 9,9'-spirobifluorene.[28] Today,
the synthesis of POPs can be done using different building blocks from very simple ones, such as
benzene (in Friedel-Crafts reaction with CH2(OMe)2),[29] to more elaborated structures, such as
27]
compounds with tetrahedral geometry (e.g. tetrakis(p-substituted-phenyl)methane,[22,
tetrakis(p-substituted-phenyl)silane[25]
or
tetrakis(p-substituted-phenyl)adamantane[27]).
28, 32]
Assembling strategies include Suzuki,[30] Sonogashira,[31] and Yamamoto,[21,
couplings, and boroxine[33] and imine[34] synthesis reactions.[35]
cross-
Compared to metal organic frameworks (MOFs), POPs are considerably more robust. Their
stability is ensured by connections made by covalent bonds instead of the chemically susceptible
coordination bonds of MOFs. Salient functionalities can also be integrated via covalent bonds.
Examples are basic N-heterocycles,[36] acidic motifs[37] and chiral entities.[23, 38]
Based on this state of the art, this study aimed the synthesis and characterization of new polymer
organic frameworks, using a tetrahedral substrate exhibiting 3,3',6,6'-tetrasubstituted-
spirobifluorene units (Scheme 1). They were coupled using either the Sonogashira protocol or
acetylenic coupling reactions. The resulted polymers were used as support for Pd to produce new
selective and reusable catalysts for the hydrogenation of several ketones (acetophenone(ACP), 4-
bromobenzophenone (4-BBP), 1,2-naphtoquinone (1,2-NQ) and 7-nitro-1-tetralone (7N-1T)). An
aromatic nitro compound (4-nitrostyrene (4-NS)) has also been hydrogenated in these
experiments. The challenge using aromatic ketones as substrates is that it is more difficult to
selectively hydrogenate the carbonyl group due to the strong positive electromer effect (+E)
induced by the presence of the aromatic group.
The new organic polymers take advantage of remnant Pd from the Sonogashira synthesis. The
additional loading of Pd was 0.5 wt.%. The resulted materials were exhaustively characterized.
This article is protected by copyright. All rights reserved.

10.1002/cctc.201801247
ChemCatChem
Results and Discussion
Synthesis of the porous organic polymers
The synthesis of key compounds (4 and 6) for the access to POP’s followed a strategy developed
in our group starting from the parent spiro compound 1 (Scheme 1).[39]
Scheme 1
The POPs with tetrasubstituted-9,9’-spirobifluorene motif exhibit different geometries according
to the positions of the reactive groups in the starting 9,9’spirobifluorene derivative. The
substituents located at positions 2,2',7,7', as it is the case in the most common derivatives, lead to
macromolecules with a planar structure, with perpendicular growing axes that are disposed in
close parallel planes, which delimit a thin sheet (Scheme 1). Substituents located at the positions
3,3',6,6' yield tetrahedral growing axes, as in tetrakis(p-substituted-phenyl)-methane and
adamantane (Scheme 2). A correction of the geometry and the synthesis of tetrahedral POPs with
derivatives of type I (having the substituents at positions 2,2’,7,7’) can be done if this substrate
reacts with reagents exhibiting an appropriate geometry, such as meta-di-substituted benzene.
This article is protected by copyright. All rights reserved.

10.1002/cctc.201801247
ChemCatChem
Scheme 2
Catalysts characterization
The investigated POP1-4 shown a good thermal stability. Except POP1, which starts to
decompose at 200 °C, all other catalysts decompose above 250 °C (Figure SI1). As the DTA
profiles demonstrated, the decomposition of these materials occurs in successive steps, specific
for each polymer (Figure SI1).
The adsorption-desorption isotherms of N2 at -196 °C of POP1-4 and the corresponding Pd- or
Pt/POP2 catalysts exhibit a type IV shape (Figure SI2) with a H4 type hysteresis loop, often
associated with mesoporous slit-like pores. The deposition of the noble metals (0.5wt% Pd or Pt)
onto POP2 did not alter the shape of the adsorption-desorption isotherms but produced a
decrease of the surface (BET and Langmuir) areas and with very small changes in the pore size
(Figure SI3). These results confirm that i) the structure/texture of the polymer is not affected by
the deposition-precipitation process and ii) the metals do not agglomerate to block the pores.
However, for Pt, the decrease of the surface area and the pore size was more evident than for Pd
which may suggest it is merely located at the pore mouth.
This article is protected by copyright. All rights reserved.

10.1002/cctc.201801247
ChemCatChem
350
300
250
200
150
100
50
a
POP2
0.04
0.035
0.03
0.025
0.02
0.015
0.01
0.005
0
b
Pd/POP2
Pt/POP2
POP2
Pd/POP2
Pt/POP2
0
0.0
0.2
0.4
0.6
0.8
1.0
10
30
50
70
90
Pore Diameter (Å)
Relative pressure (p/p0)
Figure 1. POP-based materials:(a) Nitrogen adsorption isotherms at -196 °C recorded on POP2
(purple), Pd/ POP2 (red), Pt/ POP2 (blue) (b) pore size distribution for the POP2 support and
Pd/POP2 and Pt/POP2 catalysts
Table 1. Textural properties of the investigated materials (surface areas determined from
Langmuir and Brunauer, Emmet, and Teller (BET), and pore size determined from Barrett,
Joyner, and Halenda (BJH) and Horwath−Kawazoe methods.
Sample
BET surface BJH pore size Langmuir surface Horwath−Kawazoe
area
area
pore size
(m2/g)
(Å)
(m2g-1)
(Å)
8.1
8.2
8.1
8.3
8.0
8.0
7.8
8.0
8.1
POP1
POP2
POP3
POP4
0.5% Pd/POP1
0.5% Pd/POP2
0.5% Pd/POP3
0.5% Pd/POP4
0.5% Pt/ POP2
377
583
271
205
339
522
241
321
428
21, 44
19, 41
20, 46
21,26, 44
21, 42
19, 40
20, 44
20, 43
20, 41
510
787
367
292
452
704
344
411
587
This article is protected by copyright. All rights reserved.

10.1002/cctc.201801247
ChemCatChem
Figure 2 depict the XRD patterns for the POP-based materials. They confirm the amorphous
nature of the organic polymers (Figure 2a). The absence of reflection lines of copper species
(POP1 support) and of palladium at 2θ 41° (POP2-POP4 supports) indicates that the small
loadings of the remnant Sonogashira catalyst exist only in a highly dispersed state.[18] After the
deposition-precipitation of the noble metals (Figure 2b,c), the recorded patterns shown that Pt is
deposited in a high dispersion (no line, even after the reduction, Figure 2b), while Pd
agglomerated after the reduction in hydrogen (line at 2θ 41°, Figure 2c).
POP1
POP2
POP3
POP4
a
10
20
30
40
50
60
70
80
90
2Theta (degrees)
POP2
Pd/POP2
Pd/POP2_red
c
POP2
Pt/POP2
Pt/POP2_red
b
10
20
30
40
50
60
70
80
10
20
30
40
50
60
70
80
2Theta (degrees)
2Theta (degrees)
Figure 2. X-Ray Diffraction patterns for a) POP1-4 materials, b) POP2, un-reduced and H2-
reduced Pt/POP2 and c) POP2, un-reduced and H2-reduced Pd/POP2
Figure 3 present XP spectra of the POP2 support and the investigated catalysts. For all the POP2-
POP4 polymers, the XP spectra of the Pd 3d level present the typical Pd 3d5/2 and Pd 3d5/2
doublets confirming the presence of the remnant palladium in polymers (Figure 3a, Table 2). For
This article is protected by copyright. All rights reserved.

10.1002/cctc.201801247
ChemCatChem
the reduced POP2 (Figure 3a) the peaks located at binding energies of 336.2 and 341.2 eV are
ascribed to zero-valent palladium,[40] while those at 337.7 and 342.6 eV to Pd2+ from the
palladium complex catalyst used in the synthesis of POPs.[40,41] By calculating the integration
areas of these two doublets, it can be estimated that, even after reduction, the incarcerated Pd2+ is
the major phase in these polymers (approx. 88%).
Further deposition and reduction of palladium led to an increase in the intensity of the reduced
Pd0 species (Figure 3d). The doublets at 338.3 and 343.7 eV correspond to unreduced Pd2+.[42]
However, the Pd2+ species are still dominant (65%) after the reduction in hydrogen at 200 °C. An
increase of the XPS Pd/C atomic ratio for the Pd/POP2 catalyst (Table 2) confirms the decrease
of the dispersion by the deposition/precipitation method and is in line with the XRD results.
XPS also provided information about the state of the carbon in the POPs. The deconvolution of
the C1s spectra for POP2 and Pd/POP2 samples (Figure 3 (b, e)) led to three components located
at 284.6, 285.6 and 286.6 eV, respectively, that correspond to sp2 and sp3 C and C bonded to
oxygen (C-O) species.[43] Further deposition of Pd on POP2, led to a more complex C spectrum
evidencing the presence of C=O and COOH groups (287.6, 288.7 eV)[36] that well correlated to
the concentration of the Pd2+ species.
The deconvolution of O1s spectra of POP2 and Pd/POP2 also point to the presence of the Pd2+
species (Figure 3 (c, f)). A peak with binding energy 533.2 eV was observed and is ascribed to
Pd-O. The other two components in these spectra at 531.8 and 534.6 eV and were attributed to
the oxygen bonded to aromatic structures (O-C-Ph, CH3-O-Ph).[44]
This article is protected by copyright. All rights reserved.

10.1002/cctc.201801247
ChemCatChem
Figure 3. XP spectra of the Pd3d, C1s and O1s levels for the investigated materials
Table 2. XPS binding energies and Pd/C and Pd/(Pd+Pd2+) ratios
Sample
Binding Energy
(eV)
Species
XPS atomic ratio
Pd(0)/(Pd(0)+Pd2+)x102
Chemical Pd/C
ratiox 102
Pd/C
Pd 3d5/2 Pd 3d3/2
336.2
337.7
341.2
Pd0
5 x 10-3
12
35
0.4
3.0
POP2
342.5
341.7
Pd2+ from complex
Pd0
336.4
338.3
2 x 10-2
Pd/POP2
343.7
Pd2+
TEM analysis provided more insights in the characterization of these catalysts. The deposition of
the palladium changed the morphology of the POP catalyst. TEM investigation of the POP2
sample reveals a flake-like morphology with an amorphous structure (Figure 4a), while the
deposition of palladium (see Pd/POP2 sample) changed the morphology into a ball-like
morphology (Figure 4b). It contains Pd nanoparticles with a diameter typically in the range of
This article is protected by copyright. All rights reserved.

10.1002/cctc.201801247
ChemCatChem
about 50 – 150 nm (Figure 4c,d). In the HAADF-STEM images, Pd is clearly visible as bright
patches due to atomic number contrast (Z contrast; ZPd = 46)[45] This interpretation has been
confirmed by EDXS point analysis (Figure 4d).
Figure 4. TEM images of a) the POP2 support and b) Pd/POP2 catalyst. In b), a Pd particle is
encircled. c), d) HAADF-STEM images of Pd/POP2. c) shows an area with many 50 – 150 nm
Pd nanoparticles. The EDX spectrum of the encircled particle in d) confirms the presence of Pd
there. The Cu peak results from the supporting Cu TEM grid.
In the Pt/POP2 sample, the original morphology of POP2 is well preserved as recognized in the
TEM image (Figure 5a). HAADF-STEM imaging (Figure 5b) reveals the homogeneous
distribution of small Pt clusters that appear as bright dots (Z contrast). However, although highly
This article is protected by copyright. All rights reserved.

10.1002/cctc.201801247
ChemCatChem
dispersed, the deposition of Pt caused a more advanced decrease of the surface area and the pore
size compared to Pd (Table 1). HAADF-STEM of the pure POP2 is not presented as it does not
provide any new information.
b
1 nm
C
c
Cu
Pt
Pt
Cu
O
Energy, eV
Figure 5. TEM a) and HAADF-STEM image b) of Pt/POP2. The EDX spectrum confirms the
presence of Pt there. The Cu peak results from the supporting Cu TEM grid.
Catalytic activity
Hydrogenation of 4-nitrostyrene
This article is protected by copyright. All rights reserved.

10.1002/cctc.201801247
ChemCatChem
Catalytic tests with the synthesized POP1-4 polymers carried out in the hydrogenation of 4-NS
(Scheme 3) show different activity and a full selectivity to 4-EN. Except for POP1, synthesised
following a copper-based catalytic process, all other POPs are more active than a previously
reported-adamantane based POP[16] (Table 3). These results are the consequence of the presence
of residual Pd from the POP synthesis, well incarcerated in the polymer network and able to
interact with 4-NS.[18]
Scheme 3. Potential products of the hydrogenation of 4-NS
For POP2 the conversion increases from 8.3% after 1h to 80% after 6h, for POP3 from 1% to
43%, and for POP4 from 5.3% to 79%. Doing hot filtrated tests, the ICP-OES analysis of the
reaction products indicated no palladium, thus eliminating the idea of any leaching of the active
species.[46] Very important, all catalysts were recyclable in all the investigated reactions with the
same performances (Figures SI6-10).
Table 3. Catalytic performance of POPs in the hydrogenation reaction of 4-NS
Selectivity (%) to
Time Conversion
Entry
Catalyst
(h)
(%)
4-EN
4-AS
4-EA
1
2
3
4
POP1
POP2
POP3
POP4
1
1
1
1
0.1
8.3
1
100
100
100
100
0
0
0
0
0
0
0
0
5.3
This article is protected by copyright. All rights reserved.

10.1002/cctc.201801247
ChemCatChem
5
6
POP1
POP2
6
6
0.1
80
100
100
0
0
0
0
7
8
POP3
POP4
6
6
45
79
100
100
0
0
0
0
Reaction conditions: 0.067 mmoles of 4-NS, 5 mL of heptane, 10 mg of catalyst, 25 atm H2, temperature 90 °C)
The deposition of palladium onto POPs provided more active catalysts. They hydrogenate
4-NS at 1 atm hydrogen over 1 h with total or almost total conversions (Table 4). The
comparison with a Pd/C show comparable activities but different selectivities. Pd/POP catalysts
orientate this reaction mainly to 4-EN, while Pd/C in an almost equal selectivity to 4-EN and 4-
EA. Pd/POPs also produced traces of 4-AS. Again, doing hot filtrated tests, the ICP-OES analysis
of the reaction products indicated no palladium, thus eliminating the idea of any leaching of the
active species.[46] Also important, all catalysts were recyclable with the same performances
(Figures SI4-10).
Table 4. Catalytic performance of POPs in the hydrogenation reaction of 4-NS
Entry Catalyst
Solvent
Time Conversion
Selectivity (%) to
(h)
1
(%)
99
4-EN 4-AS 4-EA
1
2
4
5
6
7
Pd/POP1 Heptane
Pd/POP2 Heptane
Pd/POP3 Heptane
Pd/POP4 Heptane
84
86
81
82
56
57
2
5
3
3
0
0
14
9
1
100
97
1
16
15
44
53
1
99
Pd/C
Pd/C
Heptane
Ethanol
1
95
1
99
Reaction conditions: 0.067 mmoles of 4-NS, 5 mL of heptane, 10 mg of catalyst, 1 atm H2, temperature 90 °C)
In spite of the small textural differences among these supports and differently to the
carbon support the catalytic tests carried out in the hydrogenation of 4-NS shown no real effect
on the palladium for the investigated hydrogenation reactions. Based on this, further catalytic
tests used as reference catalyst the Pd/POP2 one.
This article is protected by copyright. All rights reserved.

10.1002/cctc.201801247
ChemCatChem
Hydrogenation of 4-bromobenzophenone
Hydrogenation of 4-bromobenzophenone onto the same POPs provided further arguments in
favour of the absence of leaching (Scheme 4, Table 5). First step corresponds to the
hydrodehalogenation of the aromatic ring followed by the hydrogenation of the ketone. The
remnant Pd in POPs can also catalyse the hydrodehalogenation of 4-BBP to benzophenone (BP).
The conversion varied in the order POP4 > POP2 > POP3 ~ POP1 (Table 4). Among these,
POP2, although in a small extent, was able to further hydrogenate the BP to diphenylmethanol
(DPM) (selectivity of 7%).
Scheme 4. Reaction scheme of the hydrogenation of 4-BBP
Table 5. Catalytic performance of POPs in the hydrogenation of 4-BBP
Selectivity (%) to
Time Conversion
Entry
Catalyst
(h)
(%)
BP
DPM
1
2
3
4
POP1
POP2
POP3
POP4
6
6
6
6
0.6
18
15
60
100
93
0
7
0
0
100
100
Reaction conditions: 0.067 mmoles of 4-BBP, 5 mL of ethanol, 10 mg of catalyst, 25 atm H2, temperature 80°C
Catalysts that are based on POPs supports behave different in this reaction than conventional
catalysts do. Table 6 compiles comparative results for Pd/POP2 and carbon-based catalysts.
This article is protected by copyright. All rights reserved.

10.1002/cctc.201801247
ChemCatChem
While the conversions are very similar, the use of the carbon as support provides a completely
different selectivity. Pd/POP2 affords the selective hydrodehalogenation to BP with traces of
BEE while Pd/C produces a further hydrolgenoysis of the C-O group to diphenylmethane (DM).
Pd/C follows a more complex dehalogenation/hydrogenation/etherification pathway (Scheme 7).
Using Pd/C, hydrogenation of the aromatic ring has also been observed, leading to
(cyclohexylmethyl)benzene (CHMB) in small yields (Table 5). Operation at higher temperatures
affords an advanced hydrodehalogenation to BP and hydrogenation/etherification of the
produced OH groups to BEE in the detriment of DM.
Table 6. Catalytic results for 0.5 wt.% Pd catalysts for the hydrogenation of 4-BBP.
Selectivity (%) to
Temperature
Time Conversion
Entry
Catalyst
(°C)
90
(h)
6
(%)
100
99
BP
99.8
1.4
DPM BEE DM CHMB
1
2
3
4
Pd/POP2
Pd/C
-
-
0.2
0.1
-
-
90
6
95
-
3.5
-
Pd/POP2
Pd/C
140
140
6
100
100
99.8
21.6
-
0.2
6
0.2
10.5
67
0.7
Reaction conditions: 0.067 mmoles of 4-BBP, 5 mL of ethanol, 10 mg of catalyst, 25 atm H2
Table 6 provides additional evidence on the effect of temperature on the selective hydrogenation
of 4-BBP over the investigated catalysts. The remnant Pd in POPs allows high conversion only at
high temperatures. However, even in these conditions the reaction stops after
hydrodehalogenation. With Pd- and Pt/POP catalysts, the conversion of the substrate is high,
even at lower temperatures (i.e. 40 °C) with a very good selectivity in BP. Further increase of the
reaction time to 24 h generates hydrogenation of a small amount of the dehalogenated ketone as
evidenced by the formation of a very small quantity of BEE (almost 1%, Table 7). Hot filtration
confirmed again the absence of leaching. No differences were observed between Pd and Pt.
The formation of benzhydryl ethyl ether (BEE) even in the small concentrations (Table 6)
requires the presence of some catalytic acid sites. In these experiments, the acid source is only
represented by the HBr released during the dehalogenation of the substrate. Its presence was well
evidenced and quantified in the mixture collected after the reaction by the precipitation of AgBr
with AgNO3.
This article is protected by copyright. All rights reserved.

10.1002/cctc.201801247
ChemCatChem
Table 7. Performances of the investigated catalysts for the hydrogenation of 4-BBP at different
temperatures
Selectivity (%) to
Temperature Time Conversion
Entry
Catalyst
POP2
(°C)
(h)
(%)
BP
DPM
BEE
-
1
2
90
140
180
40
6
20
100.00
100.00
99.70
99.80
99.80
99.80
99.80
99.70
98.90
99.70
99.79
99.68
99.08
-
6
6
60
-
-
3
100
92
-
0.3
0.2
0.2
0.2
0.2
0.3
1.1
0.3
0.2
0.3
0.9
4
Pd/POP2
6
-
5
60
6
100
100
100
100
100
100
100
100
100
-
6
90
6
-
7
140
180
180
90
6
-
-
8
6
9
24
6
-
10
11
12
13
Pt/POP2
-
140
180
180
6
0.01
0.02
0.02
6
24
Reaction conditions: 0.067 mmoles of 4-BBP, 5 mL of ethanol, 10 mg of catalyst, 25 atm H2
The influence of the reaction time is presented for the hydrogenation of 4-BBP in the presence of
the Pd/POP2 catalyst (90 °C, ethanol, 25 atm H2) (Figure SI4). The deposition of the noble
metals onto the POPs affords a fast reaction. For 0.5 wt% Pd, the conversion reached 16% with a
This article is protected by copyright. All rights reserved.

10.1002/cctc.201801247
ChemCatChem
99% selectivity towards BP after 10 min (Figure SI4) and increases up to 95% after 2.5 h, and
99.8 % after 3 h.
Hydrogenation of acetophenone
The hydrogenation of acetophenone (ACP) on the investigated catalysts brings additional
information about their catalytic behaviour. This reaction may lead to the corresponding phenyl
alcohol as key intermediate for the production of fine chemicals, drugs and perfume
industries.[47] Obviously it is achieved via homogeneous catalysis,[48] with the cost of the
products separation and the recovery and reuse of the catalysts. For this reason, heterogeneous
catalysts are highly demanded and there are already studies concerning the selective
hydrogenation of ACP using catalysts containing noble metals (Pt, Pd, Rh, or Ru).[49] However,
even in this case, the selective hydrogenation of ACP to 1-phenylethanol (1-PE) is not trivial,
because different side reactions may take place, including the hydrogenation of the phenyl ring.
Scheme 5. Potential products of the hydrogenation of ACP
POP1-4 polymers exhibited no activity in the selective hydrogenation of ACP even after longer
reaction times meaning that the remnant highly dispersed Pd catalyst is not capable of
performance in such a reaction. However, the addition of 0.5 wt% Pd induced the required
catalytic activity and the hydrogenation of ACP occurred with a selectivity of 100 % towards the
desired 1-PE (Scheme 5).
Figure SI5 shows the evolution of the catalytic activity of Pd/POP2 as function of reaction time.
After 1h, Pd/POP2 converts 8wt% of the substrate, 87wt% after 6h and 95wt% after 24h reaction
time. A complete conversion was reached only after 30 h. Irrespective of the reaction time, the
This article is protected by copyright. All rights reserved.

10.1002/cctc.201801247
ChemCatChem
selectivity was preserved at 100% to 1-PE, and the catalyst was recyclable with the same
performances.
Another important feature of these catalysts, in line to the literature, is that Pd supported
catalysts induce the hydrogenolysis of C-OH providing ethylbenzene as a final product (Scheme
5).[50] However, this is not the case of the present catalysts which preserved the total selectivity
towards 1-PE.
Hydrogenation of 7-nitro-1-tetralone
Catalytic tests for the selective hydrogenation of 7-nitro-1-tetralone (7N-1T) using POP2 and
Pd/POP2 catalysts (Scheme 6) led to a mixture of 7-amino--tetralone (7A-T), 7-nitro-1,2,3,4-
tetrahydronaphthalene-1-ol (7N-THN) and 7-amino-1,2,3,4-tetrahydronaphthalene-1-ol (7A-
THN). The results and the reaction conditions are summarized in Table 8.
Scheme 6. Potential products of the hydrogenation of 7N-1T
The porous organic polymer is very active at relative low temperature (90 ˚C), where after 6 h
reaction time the conversion was total with a selectivity of 80% to 7A-T. The increase of the
reaction temperature up to 140 ˚C practically had no catalytic consequences. However, the
addition of 0.5 wt% Pd (Pd/POP2) changed the selectivity. At 90 ˚C, the selectivity to 7A-THN
increased at 35% on the cost of the decrease of the selectivity to 7A-T, while at 140 ˚C it
produces a further decrease in the selectivity to 7A-T forming 7N-THN (Scheme 6). This
behaviour is indicative for a structural sensitive reaction requiring larger Pd nanoparticles.
By increasing the reaction time from 6 to 24 h, in the presence of Pd/POP2, the selectivity
towards 7A-T suffered a drastic decrease. After 24 h it decreased to 36% compared to 63%
after 6h. Since the yield in the nitro alcohol remained unchanged, it is likely that the
This article is protected by copyright. All rights reserved.

10.1002/cctc.201801247
ChemCatChem
hydrogenation of 7N-1T occurs mainly via the hydrogenation of the nitro-group to 7A-
which further it is hydrogenated to the aminoalcohol.
Table 8. Hydrogenation of 7-nitro-1-tetralone onto the investigated catalysts
Selectivity (%) to
Time Conversion
t
Entry
Catalyst
POP2
(h)
(%)
(°C)
7N-THN 7A-THN
7A-T
80
1
2
3
4
5
90
140
90
6
6
100
100
100
100
100
4
3
2
8
5
16
19
35
34
59
78
Pd/ POP2
6
63
140
90
6
58
24
36
Reaction conditions: 0.067 mmoles of 7N-1T, 5 mL of ethanol, 10 mg of catalyst, 25 atm H2
Hydrogenation of 1,2-Naphtoquinone
Table 9 compiles results collected from the hydrogenation of 1,2-naphthoquinone (1,2NQ)
(Scheme 7) in the presence of Pd/POP2 and Pt/POP2. The main reaction products were 1-
hydroxy-1H-naphthalen-2-one (1H1HN) and 1,2-dyhydroxynaphthalene-1,2-diol (1,2DHN).
Hydrogenation of 1,2NQ occurred only at high temperature (see Table 8), and with relative low
conversion compared to the other substrates. However, the 0.5wt% Pt/POP2 was more active (59
versus 22% conversion) but less selective toward 1,2DHN (8 versus 72%) compared to the
corresponding Pd/POP2. Pd afforded a more advanced hydrogenation of both carbonyl groups.
This article is protected by copyright. All rights reserved.

10.1002/cctc.201801247
ChemCatChem
Scheme 7. Potential products of the hydrogenation of 1,2NQ
Table 9. Hydrogenation of 1,2-naphthoquinone onto the investigated catalysts
Selectivity (%) to
t
Time Conversion
Entry
Catalyst
(°C)
(h)
(%)
1H1HN 1,2DHN
1
2
3
4
Pd/ POP2
140
180
140
180
6
6
6
6
-
-
-
72
-
22
-
28
-
Pt/ POP2
59
92
8
Reaction conditions: 0.067 mmoles of 1,2NQ, 5 mL of ethanol, 10 mg of catalyst, 25 atm H2
The performance of the catalysts in this reaction was strongly influenced by the solvent properties,
namely, by its polarity (dielectric constant, ). Thus, the hydrogenation of 4-BBPh in ethanol (=
24.55 at 20 °C[44]) afforded higher conversions than in n-heptane (=1.92 at 20 °C[51]) (Table 10).
The superior activity of the Pd catalysts in ethanol compared to heptane is in very good
accordance with literature.[52] Changing the metal has no essential influence in this reaction.
Table 10. Performances of the investigated catalysts for the hydrogenation of 4-BBP using
different solvents
S (%)
Conversion
Time
(h)
Entry
Catalyst
Solvent
(%)
20
BP
DPM BEE
1
2
3
4
POP2_red
Ethanol
Heptane
Ethanol
Heptane
6
6
6
6
100.0
100.0
99.8
-
-
-
-
-
-
0.4
100
10
Pd/POP2_red
0.2
-
100.0
This article is protected by copyright. All rights reserved.

10.1002/cctc.201801247
ChemCatChem
5
6
Pt/POP2_red
Ethanol
Heptane
6
6
100
16
99.7
100
-
-
0.3
-
Reaction conditions: 0.067 mmoles of 4-BBP, 5 mL of solvent, 10 mg of catalyst, 25 atm H2, temperature 90 °C
Catalysts stability
[52]
The experiments considering the Sheldon’s hot filtration test.
confirmed the absence of any
leaching. Besides this, TEM characterizations did not show any rearrangement/agglomeration of
the metal nanoparticles or morphology change after the reaction.
Conclusions
Spirobifluorene-based porous organic polymer frameworks synthesized following two different
protocols (the acetylenic coupling reaction conditions and the Sonogashira cross-coupling
reaction) behaved differently in the investigated hydrogenation reactions. POP1 prepared via a
copper-catalysis protocol was completely inactive, while POP2-4 exhibited different activities in
accordance to the accessibility of the substrates to the residual Pd. The deposition of Pd led to
active and stable catalysts in the investigated reactions in which the differences in the POP
properties exhibited either very small or no effect. They were easily separated by filtration and
after re-dispersion afforded the same performances for 10 successive cycles. The performances
of these catalysts in the hydrogenation of 4-nitrostyrene, 4-bromobenzophenone, acetophenone,
7-nitro-1-tetralone and 1,2-naphtoquinone confirmed their efficiency.
However, the role of these supports show specific properties. This has been demonstrated by the
behaviour of the different 0.5wt% Pd-POP catalysts in a very good correlation to their structural
characteristics, but also by the comparison with a Pd/C catalyst with the same loading of
palladium. The catalytic experiments revealed the role of the active metal. Platinum interacts
differently with the support affording sub-nanometric particles and, in accordance, a different
catalytic behaviour reflected merely by differences in the selectivity of the hydrogenation of 1,2-
naphthoquinone.
This article is protected by copyright. All rights reserved.

10.1002/cctc.201801247
ChemCatChem
Experimental Section
Synthesis of POPs
The spirobifluorene-based covalent organic frameworks were obtained quantitatively either from
the tetraethynyl derivative 6 submitted to the acetylenic coupling reaction conditions (Scheme 8),
or via the Sonogashira cross-coupling reactions of tetraiodo derivative 4 with 1,4-
diethynylbenzene 7 or 4,4'-diethynyl-biphenyl 8 (Scheme 9).
POP1
Scheme 8
POP2
POP3
This article is protected by copyright. All rights reserved.

10.1002/cctc.201801247
ChemCatChem
Scheme 9
All attempts to obtain POPs starting from the tetraiodurated derivative 2 via the acetylenic
coupling and the Sonogashira cross-coupling reactions with 7 and 8 failed due to the geometry
constraints induced by the macromolecules. However, the Sonogashira cross-coupling protocol
was successful by reacting 2 with meta-diethynylbenzene 9 (Scheme 10) probably due to the
geometry correction and to the tetrahedral structure of POP4.
POP4
Scheme 10
Procedure for the access to POP1
The mixture formed of terminal tetraalkyne 6 (2,2',7,7'-Tetramethoxy-3,3',6,6'-tetraethynyl-9,9'-
spirobifluorene), (0.1 g, 0.17 mmoles), tetramethylethylenediamine (0.44 g, 3.8 mmoles), and
CuI (0.21 g, 1.1 mmoles) in dry DCM (20 mL) under an aerobe atmosphere (supplied by
bubbling air into the reaction mixture) was stirred at room temperature for 12 h. At the end the
solid was collected by filtration, washed with dichloromethane, methanol, water and dried to
quantitatively yield POP1.
General procedure for the access to POP2-POP4
2,2',7,7'-Tetramethoxy-3,3',6,6'-tetraiodo-9,9'-spirobifluorene 4 (0.1 g, 0.1 mmoles) was
dissolved in dry toluene (15 mL) and Et3N (1 mL), then the solution was flushed with argon for
20 min. The diethynyl derivative [1,4-diethynylbenzene 7 (0.06 g, 0.44 mmoles) for POP2; 4,4′-
diethynylbiphenyl 8 (0.09 g, 0.44 mmoles) for POP3 or 1,3-diethynylbenzene 9 (0.1 g, 0.1
mmoles) for POP4], PdCl2(PPh3)2 (11 mg, 0.016 mmoles) and CuI (3 mg, 0.016 mmoles) were
This article is protected by copyright. All rights reserved.

10.1002/cctc.201801247
ChemCatChem
added under argon atmosphere, and the reaction mixture was stirred under reflux (110 °C) for 48
h. At the end, after cooling the reaction mixture at room temperature, the solid was collected by
filtration, washed with dichloromethane, methanol and water, and dried to give quantitatively
POP2-4 as a pale brown powder.
Synthesis of Pd/POP1-4, Pt/POP2 and Pd/C catalysts via the deposition-precipitation
method
Pd/POP1-4 and Pt/POP2 catalysts (with 0.5 wt. % noble metal) were prepared starting from a 0.3
mM precursor solution [Pd(CH3COO)2 or H2PtCl6, respectively] in 30 mL of methanol. The
deposition-precipitation of the metal was achieved with an aqueous solution of ammonia
(25wt%) at pH=9 in the presence of the corresponding amount of the support (POP). The stirring
was continued for another 2h, and then the supported solid was washed with distilled water,
dried at 80 °C for 2h under vacuum and at 80 °C overnight. Finally, Pd/POP1-4 and Pt/POP2
were reduced under a hydrogen flow (30 mL/min) at 200 °C for 3h. The synthesis of the Pd/C
based catalyst was described elsewhere [18]
.
Textural and structural characterization of the catalysts
Thermogravimetric (TG) and differential thermal analysis (DTA) were performed with a
Shimadzu DTG- 60 instrument under a dry nitrogen flow (50 mL/min, from Linde, purity
99.996%) in the temperature range 25–800 ºC with a heating-up rate of 5 ºC/min. Textural
characterization of the POPs and catalysts was carried out by measuring the
adsorption−desorption isotherms of nitrogen at -196 °C on a fully computerized Micromeritics
ASAP 2020 instrument, using the BET and Langmuir formalisms. Before the analysis, the
powders were degassed at 150 °C till a pressure of 10-6 atm. Powder X-ray diffraction (XRD)
patterns were recorded on a Shimadzu XRD-7000 diffractometer using the Cu K radiation ( =
1.5418 Å, 40 kV, 40 mA) at a scanning rate of 0.10-2/min in the 2 range 10-80°. For TEM and
EDX, the samples were dispersed in ethanol and some droplets of the suspension were deposited
on a lacey carbon foil supported on a Cu grid or supported on an aluminium stub, respectively.
This article is protected by copyright. All rights reserved.

10.1002/cctc.201801247
ChemCatChem
TEM was performed on a Tecnai F30 (FEI, field emission gun (FEG), SuperTwin lens (point
resolution ca. 0.2 nm), operated at 300 kV. EDX investigations were performed with an LEO
1530 Gemini (Zeiss, operated at 1 kV) or with a Quanta 200 (FEI, operated at 5 kV) equipped
with an EDX spectrometer (EDAX). X-ray photoelectron spectroscopy (XPS) measurements
were carried out on a SPECS surface-science cluster, including an XPS spectrometer equipped
with a monochromatic Al Kα1 X-ray source (photon energy 1486.74 eV) and operating under
ultrahigh vacuum at 1.3·10-13 atm. The photoelectrons were collected by a 150 mm radius
Phoibos electron analyzer with a pass energy of 30 eV, resulting in a full width at half maximum
(FWHM) of the Au 4f7/2 core levels of 1.15 eV55. The binding energies were corrected for the
surface-charging effects during the measurements by using the C1s core level (284.6 eV) of the
adventitious carbon as an internal reference. The content of palladium was determined by ICP-
OES (Agilent Technologies, 700 Series) after calibrating the instrument with standard solutions.
Catalytic tests
The catalytic tests were carried out in the hydrogenation of a series of unsaturated compounds
(4-nitrostyrene (4-NS), (acetophenone (ACP), 4-bromobenzophenone (4-BBP), 1,2-
naphtoquinone (1,2-NQ) and 7-nitro-1-tetralone (7N-1T)) of Sigma-Aldrich purity. All the
reactions were carried out in a magnetically stirred 25 mL stainless steel autoclave. Typically, 10
mg of catalyst were added together with 0.067 mmoles of substrate and 5 mL of solvent. The
autoclave was purged with H2 for 3 times to remove the air and then pressurized with molecular
hydrogen at 25 atm. The reactions were carried out at 40-180 ºC for different reaction times
(from 0.16 to 24 h). After reaction, the catalyst and the liquid were separated by filtration and
reaction products were analysed by gas chromatography using a GC 2014 Shimadzu apparatus
equipped with a DB-5MS capillary column (0.20 mm x 50 m x 0.33 µm) and flame ionization
detector (FID).
Leaching evaluation has been carried out using the Sheldon’s hot filtration test. [52] After 4h the
catalyst was filtered while maintaining the mixture at the reaction temperature. The filtrate was
then stirred at the same temperature for an additional 4h. Quantitative analyses were carried out
by GC (to evaluate the conversion) and ICP-OES (to evaluate the leached Pd or Pt). The
recyclability of the catalysts has been checked in.
This article is protected by copyright. All rights reserved.

10.1002/cctc.201801247
ChemCatChem
Acknowledgements
CNCS/CCCDI – UEFISCDI, project numbers PN-III-P2-2.1-PED-2016-0349
Conflict of interest
The authors declare no conflict of interest.
References
[1] M. Ito, T. Ikariya, Chem. Commun. 2007, 5134-5142.
[2] a) C. Hedberg, in Mod. Reduct. Methods, Wiley-VCH Verlag GmbH & Co. KGaA, 2008, pp.
107-134; b) M. Gopiraman, S. G. Babu, Z. Khatri, K. Wei, M. Endo, R. Karvembu, I. S. Kim,
Catal. Sci. Technol. 2013, 3, 1485-1489.
[3] R. Montalvo-González, D. Chávez, G. Aguirre, M. Parra-Hake, R. Somanathan, Synth.
Commun. 2009, 39, 2737-2746.
[4] a) G. C. Bond, Chem. Soc. Rev. 1991, 20, 441-475; b) U. K. Singh, M. A. Vannice, Appl.
Catal., A:Gen. A 2001, 213, 1-24; c) P. Gallezot, D. Richard, Catal. Rev. 1998, 40, 81-126; d) A.
Corma, P. Serna, P. Concepción, J. J. Calvino, J. Am. Chem. Soc. 2008, 130, 8748-8753; e) F.
Neatu, A. Kraynov, V. I. Parvulescu, K. Kranjc, M. Kocevar, V. Ratovelomanana-Vidal, R.
Richards, Nanotechnology 2008, 19, 225702.
[5] A. Corma, P. Serna, Science 2006, 313, 332-334.
[6] a) L. M. Rossi, F. P. Silva, L. L. R. Vono, P. K. Kiyohara, E. L. Duarte, R. Itri, R. Landers,
G. Machado, Green Chem. 2007, 9, 379-385; b) F. A. Harraz, S. E. El-Hout, H. M. Killa, I. A.
Ibrahim, J. Catal. 2012, 286, 184-192; c) D. Astruc, F. Lu, R. Aranzaes Jaime, Angew. Chem.,
Int. Ed. 2005, 44, 7852-7872.
[7] R. J. White, R. Luque, V. L. Budarin, J. H. Clark, D. J. Macquarrie, Chem. Soc. Rev. 2009,
38, 481-494.
[8] a) T. T. Upadhya, S. P. Katdare, D. P. Sabde, V. Ramaswamy, A. Sudalai, Chem. Commun.
1997, 1119-1120; b) R. A. W. Johnstone, A. H. Wilby, I. D. Entwistle, Chem. Rev. 1985, 85,
129-170.
This article is protected by copyright. All rights reserved.

10.1002/cctc.201801247
ChemCatChem
[9] a) R. Prins, Chem. Rev. 2012, 112, 2714-2738; b) W. Karim, C. Spreafico, A. Kleibert, J.
Gobrecht, J. VandeVondele, Y. Ekinci, J. A. van Bokhoven, Nature 2017, 541, 68.
[10] a) M. Tian, X. Cui, M. Yuan, J. Yang, J. Ma, Z. Dong, Green Chem. 2017, 19, 1548-1554;
b) X. Chen, L. Zhang, B. Zhang, X. Guo, X. Mu, Sci. Rep. 2016, 6, 28558; c) P. Serp, M.
Corrias, P. Kalck, Appl. Catal., A:Gen. 2003, 253, 337-358; d) S. Navalon, A.
Dhakshinamoorthy, M. Alvaro, H. Garcia, Coord. Chem. Rev. 2016, 312, 99-148.
[11] a) P. Kuhn, M. Antonietti, A. Thomas, Angew. Chem. Int. Ed. 2008,47, 3450–3453; b) P.
Kuhn, A.I. Forget, D. Su, A. Thomas, M. Antonietti, J. Am. Chem. Soc. 2008, 130, 13333–
13337; c) P. Kuhn, A.I. Forget, J. Hartmann, A. Thomas, M. Antonietti, Adv. Mater. 2009, 21,
897–901; d) S. Ren, M.J. Bojdys, R. Dawson, A. Laybourn, Y.Z. Khimyak, D.J. Adams, A.I.
Cooper. Adv. Mater. 2012, 24, 2357–2361; e) R. Palkovits, M. Antonietti, P. Kuhn,
A. Thomas, F. Schuth, Angew. Chem. Int. Ed. 2009, 48, 6909–6912; f) M. Rose,
ChemCatChem 2014, 6, 1166–1182; g) J. Roeser, K. Kailasam, A. Thomas,
ChemSusChem 2012, 5, 1793–1799.
[12] a) N.B. McKeown, P.M. Budd, Chem. Soc. Rev. 2006, 35, 675-683; b) Z. Wang, G. Chem,
K.L. Ding, Chem. Rev. 2009, 109. 322-359; c) A.I. Cooper, Adv. Mater. 2009, 21, 1291-1295.
[13] S.Y. Ding, J. Gao, Q. Wang, Y. Zhang, W. G. Song, C.Y. Su, W. Wang, J. Am. Chem. Soc.
2011, 133, 19816–19822.
[14] a) P. Kaur, J.T. Hupp, S.T. Nguyen, ACS Catal. 2011, 1, 819-835; b) Z. Xie, C. Wang, K. E.
de Krafft, W. Lin, J. Am. Chem. Soc. 2011, 133, 2056-2059.
[15] a) H.-C. Ma, J.-L. Kan, G.-J. Chen, C.-X. Chen, Y.-B. Dong, Chem. Mater. 2017, 29,
6518−6524; b) G.-J. Chen, X.-B. Li, C.-C. Zhao, H.-C. Ma, J.-L. Kan, Y.-B. Xin, C.-X. Chen,
Y.-B. Dong, Inorg. Chem. 2018, 57, 2678-2685.
[16] a) M. Shunmughanathan, P. Puthiaraj, K. Pitchumani, ChemCatChem, 2015, 7, 666-673; b)
Y.-B. Zhou, C.-Y. Li, M. Lin, Y.-J. Ding, Z.-P. Zhan, Adv. Synth. Catal. 2015, 357, 2503 –2508;
c) R.S.B. Goncalves, A.B.V. de Oliveira, H.C. Sindra, B.S. Archanjo, M.E. Mendoza, L.S.A.
Carneiro, C.D. Buarque, P.M. Esteves, ChemCatChem 2016, 8, 743 – 750; d) Y.-B. Zhou, Y.-Q.
Wang, L.-C. Ning, Z.-C. Ding, W.-L. Wang, C.-K. Ding, R.-H. Li, J.-J. Chen, X. Lu, Y.-J. Ding,
Z.-P. Zhan, J. Am. Chem. Soc. 2017, 139, 3966-3969; e) Y. Monguchi, F. Wakayama, S. Ueda,
R. Ito, H. Takada, H. Inoue, A. Nakamura, Y. Sawamaa, H. Sajiki, RSC Adv. 2017, 7, 1833; f)
This article is protected by copyright. All rights reserved.

10.1002/cctc.201801247
ChemCatChem
Z.-C. Ding, C.-Y. Li, J.-J. Chen, J.-H. Zeng, H.-T. Tang, Y.-J. Ding, Z.-P. Zhan, Adv. Synth.
Catal. 2017, 359, 2280 – 2287; g) L.-P. Jing, J.-S. Sun, F. Sun, P. Chen, G. Zhu, Chem. Sci.
2018, 9, 3523–3530.
[17] W.-H. Li, C.-Y. Li, Y. Li, H.-T. Tang, H.-S. Wang, Y.-M. Pan, Y.-J. Ding, Chem. Commun.
2018, 54, 8446—8449.
[18] M. M. Trandafir, L. Pop, N. D. Hadade, M. Florea, F. Neatu, C. M. Teodorescu, B. Duraki,
J. A. van Bokhoven, I. Grosu, V. I. Parvulescu, H. Garcia, Catal. Sci. Technol. 2016, 6, 8344-
8354.
[19] a) Q. Fang, S. Gu, J. Zheng, Z. Zhuang, S. Qiu, Y. Yan, Angew. Chem., Int. Ed. 2014, 53,
2878-2882; b) L. Li, H. Zhao, R. Wang, ACS Catal. 2015, 5, 948-955.
[20] S. M. J. Rogge, A. Bavykina, J. Hajek, H. Garcia, A. I. Olivos-Suarez, A. Sepulveda-
Escribano, A. Vimont, G. Clet, P. Bazin, F. Kapteijn, M. Daturi, E. V. Ramos-Fernandez, F. X.
Llabres i Xamena, V. Van Speybroeck, J. Gascon, Chem. Soc. Rev. 2017, 46, 3134-3184.
[21] W. Lu, D. Yuan, D. Zhao, C. I. Schilling, O. Plietzsch, T. Muller, S. Bräse, J. Guenther, J.
Blümel, R. Krishna, Z. Li, H.-C. Zhou, Chem. Mater. 2010, 22, 5964-5972.
[22] a) J. Chun, S. Kang, N. Park, E. J. Park, X. Jin, K.-D. Kim, H. O. Seo, S. M. Lee, H. J. Kim,
W. H. Kwon, Y.-K. Park, J. M. Kim, Y. D. Kim, S. U. Son, J. Am. Chem. Soc. 2014, 136, 6786-
6789; b) S.-Y. Moon, H.-R. Mo, M.-K. Ahn, J.-S. Bae, E. Jeon, J.-W. Park, J. Polym. Sci., Part
A: Polym. Chem. 2013, 51, 1758-1766; c) D. Beaudoin, T. Maris, J. D. Wuest, Nat. Chem. 2013,
5, 830-834.
[23] J. Dong, Y. Liu, Y. Cui, Chem. Commun. 2014, 50, 14949-14952.
[24] T. Muller, S. Brase, RSC Adv. 2014, 4, 6886-6907.
[25] H. Yu, C. Shen, M. Tian, J. Qu, Z. Wang, Macromolecules 2012, 45, 5140-5150.
[26] R. Dawson, A. I. Cooper, D. J. Adams, Prog. Polym. Sci. 2012, 37, 530-563.
[27] D. Yuan, W. Lu, D. Zhao, H.-C. Zhou, Adv. Mater. 2011, 23, 3723-3725.
[28] J. Schmidt, M. Werner, A. Thomas, Macromolecules 2009, 42, 4426-4429.
[29] R. T. Woodward, L. A. Stevens, R. Dawson, M. Vijayaraghavan, T. Hasell, I. P.
Silverwood, A. V. Ewing, T. Ratvijitvech, J. D. Exley, S. Y. Chong, F. Blanc, D. J. Adams, S. G.
Kazarian, C. E. Snape, T. C. Drage, A. I. Cooper, J. Am. Chem. Soc. 2014, 136, 9028-9035.
This article is protected by copyright. All rights reserved.

10.1002/cctc.201801247
ChemCatChem
[30] a) Q. Chen, M. Luo, T. Wang, J.-X. Wang, D. Zhou, Y. Han, C.-S. Zhang, C.-G. Yan, B.-H.
Han, Macromolecules 2011, 44, 5573-5577; b) K. V. Rao, S. Mohapatra, C. Kulkarni, T. K.
Maji, S. J. George, J. Mater. Chem. 2011, 21, 12958-12963.
[31] a) J.-X. Jiang, F. Su, A. Trewin, C. D. Wood, H. Niu, J. T. A. Jones, Y. Z. Khimyak, A. I.
Cooper, J. Am. Chem. Soc. 2008, 130, 7710-7720; b) R. Dawson, A. Laybourn, R. Clowes, Y. Z.
Khimyak, D. J. Adams, A. I. Cooper, Macromolecules 2009, 42, 8809-8816.
[32] T. Ben, H. Ren, S. Ma, D. Cao, J. Lan, X. Jing, W. Wang, J. Xu, F. Deng, J. M. Simmons,
S. Qiu, G. Zhu, Angew. Chem., Int. Ed. 2009, 48, 9457-9460.
[33] a) E. L. Spitler, M. R. Giovino, S. L. White, W. R. Dichtel, Chem. Sci. 2011, 2, 1588-1593;
b) A. L. Korich, P. M. Iovine, Dalton Trans. 2010, 39, 1423-1431; c) M. K. Smith, B. H.
Northrop, Chem. Mater. 2014, 26, 3781-3795.
[34] a) G. Das, D. Balaji Shinde, S. Kandambeth, B. P. Biswal, R. Banerjee, Chem. Commun.
2014, 50, 12615-12618; b) Y.-B. Zhang, J. Su, H. Furukawa, Y. Yun, F. Gándara, A. Duong, X.
Zou, O. M. Yaghi, J. Am. Chem. Soc. 2013, 135, 16336-16339; c) M. E. Belowich, J. F.
Stoddart, Chem. Soc. Rev. 2012, 41, 2003-2024.
[35] X. Zhu, C. Tian, T. Jin, J. Wang, S. M. Mahurin, W. Mei, Y. Xiong, J. Hu, X. Feng, H. Liu,
S. Dai, Chem. Commun. 2014, 50, 15055-15058.
[36] a) Y. Du, K. Mao, P. Kamakoti, P. Ravikovitch, C. Paur, S. Cundy, Q. Li, D. Calabro,
Chem. Commun. 2012, 48, 4606-4608; b) W. Li, H. Shi, J. Zhang, ChemPhysChem 2014, 15,
1772-1778; c) Z. Xie, C. Wang, K. E. deKrafft, W. Lin, J. Am. Chem. Soc. 2011, 133, 2056-
2059; d) J. X. Jiang, C. Wang, A. Laybourn, T. Hasell, R. Clowes, Z. Khimyak Yaroslav, J.
Xiao, J. Higgins Simon, J. Adams Dave, I. Cooper Andrew, Angew. Chem., Int. Ed. 2010, 50,
1072-1075.
[37] P. Kaur, J. T. Hupp, S. T. Nguyen, ACS Catal. 2011, 1, 819-835.
[38] L. Ma, M. M. Wanderley, W. Lin, ACS Catal. 2011, 1, 691-697.
[39] L. Pop, F. Dumitru, N. D. Hădade, Y.-M. Legrand, A. van der Lee, M. Barboiu, I. Grosu,
Org. Lett. 2015, 17, 3494-3497.
[40] J. C. Bertolini, P. Delichere, B. C. Khanra, J. Massardier, C. Noupa, B. Tardy, Catal. Lett.
1990, 6, 215-223.
[39] J. Chen, W. Zhang, L. Chen, L. Ma, H. Gao, T. Wang, ChemPlusChem 2012, 78, 142-148.
This article is protected by copyright. All rights reserved.