Accelerated Anti-Markovnikov Alkene Hydrosilylation with Humic-Acid-Supported Electron-Deficient Platinum Single Atoms

Article abstract of DOI:10.1002/anie.202109689

The hydrosilylation reaction is one of the largest-scale applications of homogeneous catalysis, and Pt homogeneous catalysts have been widely used in this reaction for the commercial manufacture of silicon products. However, homogeneous Pt catalysts result in considerable problems, such as undesired side reactions, unacceptable catalyst residues and disposable platinum consumption. Here, we synthesized electron-deficient Pt single atoms supported on humic matter (Pt₁@AHA_U_400), and the catalyst was used in hydrosilylation reactions, which showed super activity (turnover frequency as high as 3.0×10⁷ h^?1) and selectivity (>99 %). Density functional theory calculations reveal that the high performance of the catalyst results from the atomic dispersion of Pt and the electron deficiency of the Pt₁ atoms, which is different from conventional Pt nanoscale catalysts. Excellent performance is maintained during recycle experiments, indicating the high stability of the catalyst.

Full text of DOI:10.1002/anie.202109689

A Journal of the Gesellschaft Deutscher Chemiker
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Accepted Article
Title: Accelerated Anti-Markovnikov Alkene Hydrosilylation with Humic-
Acid-Supported Electron Deficient Platinum Single Atoms
Authors: Kairui Liu, Bolortuya Badamdorj, Fan Yang, Michael J. Janik,
and Markus Antonietti
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10.1002/anie.202109689
Angewandte Chemie International Edition
RESEARCH ARTICLE
Accelerated Anti-Markovnikov Alkene Hydrosilylation with Humic-
Acid-Supported Electron Deficient Platinum Single Atoms
Kairui Liu,*[a] Bolortuya Badamdorj,[a] Fan Yang,*[b] Michael J. Janik,*[c] and Markus Antonietti*[a]
[a]
Dr. K. Liu, B. Badamdorj, Prof. M. Antonietti
Department Department of Colloid Chemistry
Institution Max Planck Institute of Colloids and Interfaces
Potsdam 14476, Germany
E-mail: Kairui.Liu@mpikg.mpg.de
Markus.Antonietti@mpikg.mpg.de
Prof. F. Yang
School of Water Conservancy and Civil Engineering
Northeast Agricultural University
Harbin 150030, China
[b]
[c]
E-mail: yangfan@neau.edu.cn
Prof. M. J. Janik
Department of Chemical Engineering
Pennsylvania State University
PA 16802, USA
E-mail: mjj13@psu.edu
Supporting information for this article is given via a link at the end of the document.
Abstract: Hydrosilylation reaction is one of the largest-scale
applications of homogeneous catalysis, and Pt homogeneous catalyst
has been widely used in this reaction for the commercial manufacture
of silicon products. However, homogeneous Pt catalysts results in
considerable problems, such as undesired side reactions,
However, the activity is lower or comparable to their parental
Karstedt Pt catalyst.[2a, 6] Moreover, homogeneous Pt catalysts are
hard to recycle, and will inevitably bring in unacceptable catalyst
residues in the products, which is a waste of the rare noble metal.
These drawbacks promote the development of heterogeneous
unacceptable catalyst residues and disposable platinum consumption. catalysts, which is featured in facile separation and recycling.
Here, we synthesized electron deficient Pt single atoms supported on
humic matter (Pt1@AHA_U_400), and the catalyst was used in
hydrosilylation reaction, which showed super activity (turnover
frequency as high as 3.0 × 107 h-1) and selectivity (>99%). Density
functional theory calculations reveal that the high performance of the
catalyst results from the atomic dispersion of Pt and the electron
deficiency of the Pt1 atoms, which is different from conventional Pt
nanoscale catalysts. Excellent performance is maintained during
recycle experiments, indicating the high stability of the catalyst.
However, low efficiency of metal atom utilization and active
species leaching leads to the unsatisfying performance of current
heterogeneous catalysts.
Single atom catalyst combines of the advantages of
homogeneous and heterogeneous catalysts with 100% atom
utilization, and shows unique activity and selectivity in catalysis
resulting from the special and uniform structures.[7] Downsizing
nanoclusters to single metal atoms not only reducing the
accessible neighboring adsorption and reaction sites for reactants,
which may otherwise result in stronger adsorption and higher
energy barrier for reaction, but also changing the electron density
state of the catalytic sites by adjusting the surrounding ligands.[7b]
For the synthesis of single atom catalyst, supports with suitable
surface functional groups which can coordinate to metal atoms
are needed to overcome the high surface energy of single atom.
Humin/humic acid, which accounts for up to 80 wt% of the total
organic matter in soil, is a promising and sustainable carbon
material for catalysis.[8] As a complex mixture of polymers rich in
carboxylates and phenolate groups, it can chelate and bind to
metal ions with high binding constants, especially for iron and
noble metals.[8,9] With other delicate modification, humic acid can
serve as a benign support with various functional groups in single
atom catalysis. However, owing to the rich phenolic and
carboxylic groups and low molecular weights, humic acid
dissolves well in base or polar organic solvents, which would
result in “enzyme-like” operation conditions, but restricts the
traditional processes of heterogeneous catalysis. To use it as a
traditional heterogeneous catalyst, crosslinking with moderate
thermal condensation is to be applied.
Introduction
Alkene hydrosilylation, the addition of a silicon hydride (Si-H) to
a carbon-carbon double bond, is one of the largest-scale industrial
applications of homogeneous catalysis, and Pt homogeneous
catalyst is widely used in this reaction for the commercial
manufacture of silicon products.[1] The worldwide silicone industry
consumes nearly 5.6 tons of platinum annually,[2] and the most
widely used catalysts for the commercial synthesis of silicones are
the so-called Speier Pt catalyst and Karstedt Pt catalyst.[3]
However, these two catalysts suffer from side reactions, such as
alkene isomerization and dehydrogenative silylation,[4] which
make subsequent purification steps necessary that are both
energy and cost intensive. Meanwhile, colloidal Pt species often
form during the hydrosilylation reaction and lead to additional side
reactions and coloration of the final product, which is also an
indication of catalyst deactivation.[5] Modified Karstedt Pt catalysts
show an improved product selectivity and catalyst stability.
1
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To protect the acidic function groups in humic acid and provide
a high temperature solvent reaction medium, molten-salts can be
used.[10] The coordination between carboxyl/phenolate groups of
humic acid and metal ions may promote the dissolution of humic
acid oligomers in molten-salts, while metal salt ligation protects
the functional groups at relative high condensation temperatures.
The addition of crosslinkers link the humic acid oligomers together
and may result in a porous humic acid framework, thus increasing
molecular weight, strength, and heterogeneity of the potential
catalytic system. Previously, we described the generation of
artificial humic acid (AHA) by artificial hydrogeochemistry at
moderate temperature and autogenous pressures in water.[11]
Herein, we show the synthesis of humic acid based porous carbon
frameworks with urea (AHA_U_400) as a crosslinkers in an ionic
molten-salt (MS) medium by fine-tuning the synthesis conditions.
A Pt single atom model catalyst is prepared by using AHA_U_400
as a support. The catalyst is applied in hydrosilylation reaction,
and showed remarkable activity and selectivity.
Results and Discussion
AHA_U_400 synthesis and characterization
AHA was synthesized from Liriodendron tulipifera as
described by Yang et al.[11] The phenol or hydroxyl groups of AHA
(Fig. 1a) can be cross-linked at elevated temperatures via
carbonylation reaction with urea[12] to give a particular, porous,
non swellable and thereby hard carbonaceous material. Fig. 1b
shows that when the condensation temperature increased to
400°C, AHA completely transformed into such hard carbon
material as AHA_U_400 treated with base (NaOH, 1M) only gave
a transparent solution phase, without dissolution. Elemental
analysis shows that condensation at 400°C resulted in a lowering
of O-content from 23.68% to 14.06% (Table S1), which we
attribute to decarboxylation and partial dehydration.[13] However,
the N content increased, which we assign to the carbonylation
reaction with urea with the preservation of one nitrogen.[12] Fig. 1c
shows the FTIR of AHA condensed and cross-linked at different
temperatures. The broad absorption band at 3200-3600 cm−1 is
caused by the stretching vibrations of the -OH groups.[14] With the
increasing of the condensation temperature, the alkyl C-H
vibration peak between 2820 cm-1 and 2930 cm-1 and the CAlkyl-O
vibration peak at 1108 cm-1 disappeared, which may point to water
elimination from carbohydrate-based humic acid fragments.[13]
The peak at 1698 cm-1 representing the C=O bond in carboxylic
groups also disappeared,[11] indicating the elimination of
Fig. 1 AHA_U_400 synthesis and characterizations. (a) AHA and the
carbonylation reaction between phenol/hydroxyl groups of AHA and urea. (b)
Images for the dissolving of AHA condensed at different temperatures in
NaOH solution (1M). (c) FTIR spectra of AHA condensed at different
temperatures. (d, e, f) XPS spectra of C1s, O1s and N1s for AHA_U_400.
(g) Solid state 13C NMR spectra of AHA_U_400.
corresponds to C=O[18] and C-O,[19] respectively. The N1s can be
decomposed into two peaks located at 399.9 and 398.4 eV,
corresponding to amide and amino acid ester generated by
carbonylation reaction with urea, respectively.[20] Solid state 13C
NMR was also performed to investigate the C species in
AHA_U_400 (Fig. 1g). Obviously, aromatic carbon is dominant,
which is consistent with the XPS and FTIR data. Meanwhile, alkyl
C (0-44 ppm) and ketone/amidic C (188-230 ppm) were also
detected.[21] The absence of peak between 162-188 ppm
corresponding to COOH is consistent with the FTIR results.[21]
SEM images in Fig. 2 show the morphology changes of AHA
before and after condensation in ZnCl2-KCl salt melts. Obviously,
AHA_U_400 is made up from much smaller particles compared to
the isolated AHA, and the material becomes more porous while
the bigger pores start to be visible on the surface texture of the
particles, which points to the strong interaction with the salt
melts.[13] As it is shown in Table S2 and Fig. S1a, the BET surface
area of AHA_U_400 is more than two orders higher than that of
AHA, illustrating the successful formation of a carbon framework
with the salt melt as a porogen. Pore size distribution showed that
the majority of the pores are micropores (Fig. S1b).
carboxylic groups of AHA at high temperature. However, the CAryl
-
O vibration peak around 1210 cm-1 and the aromatic C=C
vibration peak around 1600 cm-1 still show strong adsorption,[14]
suggesting the phenolic part of the AHA remained at 400°C.
Although some decrease of the intensity of phenolic hydroxyls
was found, the acid concentration of phenolic hydroxyls on
AHA_U_400 is still as high as 2.4 mmol/g (Table S2). Consistent
with the lowering of oxygen content and FTIR results, almost no
carboxylic acid was found on AHA_U_400 during titration.
XPS was conducted to further confirm the surface chemistry of
AHA_U_400 (Fig. 1d-f). Three types of carbon species are shown
in C1s spectrum: the peak at 284.6 eV represents the aromatic
carbon;[15] the peak at 285.6 eV originates from the C in C-O;[16]
the peak at 287.5 represents the C in -C=O.[17] The O1s can be
decomposed into two peaks located at 531.7 and 533.1 eV, which
Without urea, heating also results in the appearance of big
pores (AHA_400, Fig. S2). However, the pores are much larger,
2
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as pore growth is not stopped by the onset of cross-linking ahead
of thermal elimination of water and CO2, and the BET surface area
is consequently only around 1/3 of that of AHA_U_400 (Fig. S1a
and Table S2). Therefore, urea cross-linking is beneficial to create
a heterogeneous catalyst support, while the carbonylation
reaction between urea and AHA should promote the restructure
of the AHA morphology. Meanwhile, compared to the AHA_400,
more phenolic groups were retained for AHA_U_400 during the
thermal condensation process (Fig. S3). Thermo-gravimetric
analysis (TGA) on AHA_U_400 shows only 2.51% reoccurring
weight loss from 160°C to 380°C, illustrating the high stability of
AHA_U_400 at elevated temperatures (Fig. S4).
Pt1@AHA_U_400 synthesis and characterization
The high phenolic content of AHA_U_400 makes it a favorable
support to stabilize metal atoms, even as single atom catalysts.[7b]
On the long run, we of course want to use iron for this purpose,
but here due to the much better visibility and developed catalytical
unit operation to reference to, we decided to graft with Pt first.
H2PtCl6 was mixed with ethanol, water and AHA_U_400, and
stirred for 2 h at room temperature. Ethanol was chosen for the
reduction of H2PtCl6. After that, the catalyst was filtrated and
vacuum dried at 60°C for 24 h.
XRD indicates the absence of any peaks related to Pt particles
(Fig. S5), while ICP-OES gave a Pt loading of 1 wt% with
corresponding amount of H2PtCl6 precursor used. A more visual
appearance is obtained by high resolution transmission electron
microscopy (HRTEM). Fig. 3a-d shows high-angle annular dark-
Fig. 2 Representative SEM images of AHA (a, b, c) and AHA_U_400 (d, e,
f).
field and bright-field scanning HRTEM
images
of
Pt1@AHA_U_400.
As
manifested by the bright spots, Pt atoms
are found atomically dispersed on
AHA_U_400, sometimes we might see
some Pt atoms a little close to each other,
which may result from projection overlaps
or “beam shower” pretreatment[22] of the
sample, but nanoparticles were absent.
To further confirm the atomically
dispersion of Pt on AHA_U_400, in situ
diffuse reflectance infrared Fourier
transform (DRIFT) spectroscopy of CO
adsorption on Pt1@AHA_U_400 was
performed (Fig. 3e). Depending on the Pt
nuclearity in the particles, adsorbed CO
on Pt may form linear Pt-CO, doubly
bridged Pt2CO, and triply bridged Pt3CO
on the surface of Pt clusters and
nanoparticles.[7a] However, only one peak
at 2098 cm-1 corresponding to the linearly
adsorbed CO on Pt1@AHA_U_400 was
detected (Fig. 3e). The absence of
bridged CO adsorption peak between
1800 and 1900 cm-1 implies the absence
of Pt clusters and nanoparticles. There is
almost no shift with more CO adsorption,
further demonstrating the atomic
dispersion of Pt on AHA_U_400.
Moreover, the high wavenumber (2098
cm-1) implies that the Pt1 atom is electron
deficient, which is consistent with the
Fig. 3 Structural characterizations of Pt1@AHA_U_400. High-angle annular dark-field (a, c) and bright-
field (b, d) STEM images of 1 wt% Pt1@AHA_U_400. (e) In situ diffuse reflectance infrared Fourier
transform (DRIFT) spectroscopy of CO adsorption on 1 wt% Pt1@AHA_U_400. (f) X-ray photoelectron
spectra of 1 wt% Pt1@ AHA_U_400. (g) Pt L3-edge EXAFS spectra in R space of Pt foil and 1 wt% Pt1@
AHA_U_400. Pt foil was used as the reference. (h) Structural model of Pt1@ AHA_U_400 simulated by
DFT calculations.
3
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XPS results. A peak at 72.54 eV (Pt 4f7/2), which is 1.34 eV higher
than that of bulk Pt metal (71.20 eV) and 0.66 eV lower than that
of Pt(II) (73.2 eV),[23] indicating missing electron density in the Pt
center, which is may due to electron donation to the support (Fig.
3f).
Table 1: Hydrosilylation of terminal olefins catalyzed by Pt1@AHA_U_400[a]
To determine the electronic and coordination structures of Pt
atoms in Pt1@AHA_U_400 catalysts, extended X-ray absorption
fine structure (EXAFS) spectra were measured (r space, Fig. 3g).
There is one prominent peak at 1.9 Å, which is longer than the Pt-
O distance for PtO2 in FT-EXAFS results (~1.7 Å).[24] Far infrared
spectra (Fig. S6) and XPS spectra of Cl 2p (Fig. S7) show that
some chlorines are still weakly coordinating to Pt1 atoms in
Pt1@AHA_U_400. Therefore, the peak at 1.9 Å may be a mixed
result of the Pt-O and Pt-Cl shells which are close to each other.
No other typical peaks for Pt–Pt bonds at longer distances (>2.5
Å) were observed, revealing the isolation of Pt atoms throughout
the whole Pt1@AHA_U_400.
Although AHA_U_400 can be ligated with metal ions,
AHA_400 showed no ligation ability with metal ions. Considering
the introduction of carbonyl group through carbonylation reaction
between AHA and urea (Fig. 1a) and some chlorines still
coordinates to Pt1 center, a possible local structure model of Pt
single atoms in AHA_U_400 was constructed and optimized by
DFT (Fig. 3h). The anchoring site of AHA_U_400 was modeled
as deprotonated salicylamide, and DFT calculation shows that Pt
coordinated by two unsaturated O atoms, as well as one Cl- and
one HCl moiety is the most stable structure (Table. S4). This
model agrees well with our EXAFS results (Fig. 3g), which
indicates a Pt-O coordination number (CN) of 1.9 and a Pt-Cl CN
of 2.2 (Table S3). Bader charge analysis shows the Pt center is
electron deficient with around + 0.9 e, which is consistent with the
XPS results. This model is used below as a starting structure to
be utilized in density functional theory calculations for the
hydrosilylation process.
[a] Experiments were performed at 4 mmol scale: 1 wt% Pt1@ AHA_U_400
catalyst, silane/olefin = 1.1 (mol/mol), temperature = 70oC. The products
yield and selectivity were determined by 1H NMR analysis using N,N-
dimethylaniline as internal standard. [b] Based on olefin substrate. [c] TOF
values were calculated based on T yield, and the calculation method was
detailed in Fig. S12. [d] To eliminate the influence of mass transfer,
improve solid-liquid contact and easy to weigh the catalyst, 0.25 wt% Pt1@
AHA_U_400 catalyst was used. [e] Temperature = 50oC. [f] 0.25 wt% Pt1@
AHA_U_400 catalyst was used, and the experiment is performed on 40
mmol scale (base on olefin). [g] Karstedt catalyst was used, and the
experiment is performed on 40 mmol scale (base on olefin). [h] 1 wt%
PtNP@AHA_U_400 catalyst. For 1-octene, only trace amount of olefin
isomerization products was detected. For styrene, the side product is α-
adduct. For other terminal alkenes, the low selectivity may come from the
decomposition of the alkenes in the reaction condition.
Catalytic properties of Pt1@AHA_U_400 for hydrosilylation
The catalytic efficiency of Pt1@AHA_U_400 was then
evaluated in hydrosilylation reaction for a wide range for both
alkenes and silanes (Table 1). AHA_U_400 shows no catalytic
ability for the benchmark reaction between 1-octene and
(Me3SiO)2MeSiH. However, Pt1@AHA_U_400 shows an ultrahigh
activity with a high selectivity (99%) for the benchmark reaction
between 1-octene and (Me3SiO)2MeSiH (Entry 4, Table 1). The
turnover frequency (TOF) is as high as 9.8 × 106 h-1. 17% product
yield can be achieved in 1 h even when the catalyst using amount
is very low (Entry 5, Table 1), which is more than 3 times higher
than that of Karstedt Pt catalyst (Entry 6, Table 1), and to our
knowledge one of the highest ever reported for heterogenous
catalysis.
Pt 4f (Fig. S11b) shows the Pt1 center is still electron deficient
after reaction, which may result from the oxidative addition of
excess silane onto the Pt1 center (molar ratio of olefin to silane is
1:1.1 before reaction). It also indicates no Pt nanoparticles or
clusters are formed during the reaction. XPS spectra of Cl 2p (Fig.
S11a) shows that the intensity of the peak corresponding to
inorganic chlorine bonding to Pt1 decreased greatly after reaction,
indicating olefin or silane replace chlorine to coordinate to the Pt1
during the reaction.
In contrast, the reference system PtNP@ AHA_U_400 (Fig. S8)
showed no reactions even in 30 mins (Entry 7, Table 1), indicating
that the active site is not the Pt as such, but single Pt atoms
immobilized on the artificial humic acid framework. For
Pt1@AHA_U_400, no special activation period was needed, and
the solution remained colorless and transparent after reaction and
separation of the heterogeneous catalyst, indicating high stability
of Pt1@AHA_U_400 during the hydrosilylation process.[2a, 5] High
activity and selectivity were both maintained even when the
catalyst was recycled for 6 times (Fig. S9), indicating the high
stability of the catalyst. STEM images of the spent catalyst show
no aggregation of the Pt single atoms (Fig. S10). XPS spectra of
When phenyldimethylsilane was used, the TOF value reached
3.0 × 107 h-1 (Entry 1, Table 1), which is about 106 times that of
the phosphines modified Karstedt Pt catalyst,[25] and 100 times
that of single atom based heterogeneous platinum catalyst
(120oC).[26] Moreover, Pt1@AHA_U_400 showed 100% selectivity
for the 1,2-epoxy-4-vinylcyclohexane (Entries 13&14, Table 1),
where opening/polymerization of the sensitive epoxide function is
observed when Karstedt catalysts were used.[2a] At the same time,
the catalyst also showed superior performance in hydrosilylation
of diverse terminal olefins with functional groups (Entries 10-12
and 15-19, Table 1). Pt leaching test (Table 1, Entry 3) shows very
low level of Pt (0.08 ppm, corresponding to about 1.5% of the
4
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10.1002/anie.202109689
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RESEARCH ARTICLE
initial Pt adding amount) in the crude reaction solution, and almost
no conversion (< 1%) is obtained by using the crude reaction
solution as catalyst, indicating the atomically dispersed Pt on
AHA_U_400 is the real catalytic sites.
leads to silane and olefin adsorbing on different Pt atoms,
resulting in much stronger adsorption (Fig. S15, 4.3 vs 3.5 eV)
and higher energy barrier for the hydrosilylation on
PtNP@AHA_U_400 (Fig. S15). The Pt-C bond length for olefin on
PtNP@AHA_U_400 (2.11 Å) is shorter than that on
Pt1@AHA_U_400 (2.17 Å), indicating stronger coordination
strength. However, moderate coordination strength is beneficial
for rapid hydrosilylation, and too strong or too weak coordination
both slow the reaction.[29] Meanwhile, Bader charge analysis
shows that the charge on Pt (+0.42 e) for the initial reaction
structure of Pt1@AHA_U_400 is much higher than that of Karstedt
catalyst (-0.10 e), which may be beneficial for lowering energy
barrier by optimizing the eletron structure of the transition state
(TS).
Density functional theory studies
Conclusion
A
humic acid based carbonaceous support material
AHA_U_400 was prepared through mild thermal condensation
and cross-linking between artificial humic acid and urea, and the
material proved to enable the preparation of stable Pt single atom
catalyst Pt1@AHA_U_400. HAADF-STEM, CO-DRIFT, EXAFS,
XPS and FIR prove the formation of Pt1 and the chemical
environment of Pt1. The catalyst shows ultrahigh activity and
selectivity in hydrosilylation reaction. DFT calculation show that
the high performance of the catalyst can be attributed to the
atomic dispersion of Pt and the electron deficiency of the Pt1
atoms.
Fig. 4 Reaction paths for hydrosilylation reactions on Pt1@AHA_U_400
and Karstedt’s Pt catalyst. The navy blue, yellow, red, bright blue, gray and
white balls represent Pt, Si, O, N, C and H atoms, respectively. To highlight
the reaction sites, green and pink balls represent the C1 and C2 in
CH2=CH-CH3, respectively. For simplification, propylene and
(MeO)2MeSiH
were
used
to
represent
octene
and
(Me3SiO)2MeSiH/(CH3CH2O)2CH3SiH, respectively. For the hydrosilylation
on Karstedt catalyst, Pt stabilized by olefin model is used according to
literature, and CH2=CH-CH3 was used not only as reactant but also as
ligand.[5]
To elucidate the reaction mechanism of hydrosilylation reaction
on Pt1@AHA_U_400, density functional theory (DFT) calculations
were performed. For comparison, hydrosilylations on Karstedt’s
Pt catalyst and PtNP@AHA_U_400 (Pt (111) surface) were also
calculated. As proposed by Chalk and Harrod, the reaction
mechanism of Pt-catalyzed alkene hydrosilylation can be divided
into three sequential steps: Si-H oxidation addition to Pt, alkene
insertion into the Pt-H bond and Si-C reductive elimination.[27]
However, for modified Chalk-Harrod mechanism, the second step
is alkene insertion into the Pt-Si bond followed by the C-H
reductive elimination as the third step.[28] Both mechanisms on
Pt1@AHA_U_400, Karstedt’s Pt catalyst and PtNP@AHA_U_400
were examined by DFT.
We initiated the reaction by binding silane to the single Pt atom,
with the model matching that in Fig. 3i with chlorine ligands
dissociated and replaced by silane. As shown in Fig. 4 and Fig.
S13, for Pt1@AHA_U_400, the modified Chalk-Harrod
mechanism is more favorable than the Chalk-Harrod mechanism
with much lower energy barrier (0.94 vs 1.35 eV). However, for
Karstedt’ Pt catalyst (Fig. 4 and Fig. S14) and Pt (111) (Fig. S15
and Fig. S16), Chalk-Harrod mechanism is more favorable.
Obviously, the energy barriers for hydrosilylaiton on Karstedt’ Pt
catalyst and Pt (111) are much higher than that on
Pt1@AHA_U_400 (Fig. 4, 1.22 vs 0.94 eV; Fig. S15, 2.92 vs 0.94
eV), which is consistent with their lower activity for hydrosilylation
reaction (Entries 6, 7 and 9, Table 1).
Acknowledgements
The authors acknowledge the financial support from the Max-
Planck Society and the support of the technicians in MPIKG.
Conflict of interest
The authors declare no conflict of interest.
Keywords: artificial humic acid • Pt single atom • urea •
heterogeneous catalysis • hydrosilylation
[1]
a) B. Marciniec, Coord. Chem. Rev. 2005, 249, 2374-2390; b) L. N. Lewis,
J. Stein, Y. Gao, R. E. Colborn, G. Hutchins, Platinum. Met. Rev 1997,
41, 66-75.
[2]
a) I. E. Marko, S. b. Ste´rin, O. Buisine, G. r. Mignani, P. Branlard, B.
Tinant, J.-P. Declercq, Science 2002, 298, 204-206; b) A. M. Tondreau,
C. C. Atienza, K. J. Weller, S. A. Nye, K. M. Lewis, J. G. Delis, P. J. Chirik,
Science 2012, 335, 567-570.
[3]
a) J. L. Speier, J. A. Webster, G. H. Barnes, J. Am. Chem. Soc. 1957, 79,
974-979; b) B. D. Karstedt, N. Scotia, (Ed.: U. S. P. Office), USA, 1973.
X. Du, Z. Huang, ACS Catal. 2017, 7, 1227-1243.
[4]
[5]
J. Stein, L. N. Lewis, Y. Gao, R. A. Scott, J. Am. Chem. Soc. 1999, 121,
3693-3703.
The ultrahigh activity of Pt1@AHA_U_400 catalyst may be
attributed to the atomic dispersion of isolated Pt atoms and the
electron deficiency of the Pt1 atoms. Compared to
Pt1@AHA_U_400, the accessible neighboring adsorption Pt sites
[6]
a) T. Troadec, A. Prades, R. Rodriguez, R. Mirgalet, A. Baceiredo, N.
Saffon-Merceron, V. Branchadell, T. Kato, Inorg. Chem. 2016, 55, 8234-
8240; b) T. Iimura, N. Akasaka, T. Kosai, T. Iwamoto, Dalton Trans. 2017,
5
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RESEARCH ARTICLE
46, 8868-8874.
[7]
a) B. Qiao, A. Wang, X. Yang, L. F. Allard, Z. Jiang, Y. Cui, J. Liu, J. Li, T.
Zhang, Nat. Chem. 2011, 3, 634-641; b) A. Wang, J. Li, T. Zhang, Nat.
Rev. Chem. 2018, 2, 65-81; c) R. Lang, T. Li, D. Matsumura, S. Miao, Y.
Ren, Y. T. Cui, Y. Tan, B. Qiao, L. Li, A. Wang, X. Wang, T. Zhang, Angew.
Chem. 2016, 128, 16288-16292; Angew. Chem. Int. Ed. 2016, 55, 16054-
16058; d) Z. Chen, E. Vorobyeva, S. Mitchell, E. Fako, M. A. Ortuno, N.
Lopez, S. M. Collins, P. A. Midgley, S. Richard, G. Vile, J. Perez-Ramirez,
Nat. Nanotechnol. 2018, 13, 702-707; e) F. Chen, X. Jiang, L. Zhang, R.
Lang, B. Qiao, Chin. J. Catal. 2018, 39, 893-898.
[8]
[9]
F. Yang, M. Antonietti, Prog. Polym. Sci. 2020, 100, 101182.
F. Yang, S. Zhang, J. Song, Q. Du, G. Li, N. V. Tarakina, M. Antonietti,
Angew. Chem. 2019, 131, 18989-18992; Angew. Chem. Int. Ed. 2019,
58, 18813-18816.
[10] X. Liu, N. Fechler, M. Antonietti, Chem. Soc. Rev. 2013, 42, 8237-8265.
[11] F. Yang, S. Zhang, K. Cheng, M. Antonietti, Sci. Total Environ. 2019, 686,
1140-1151.
[12] W. Peng, W. Zhao, N. Zhao, J. Li, F. Xiao, W. Wei, Y. Sun, Catal. Commun.
2008, 9, 1219-1223.
[13] X. Liu, C. Giordano, M. Antonietti, Small 2014, 10, 193-200.
[14] M. Tatzber, M. Stemmer, H. Spiegel, C. Katzlberger, G. Haberhauer, A.
Mentler, M. H. Gerzabek, J. Plant Nutr. Soil Sci. 2007, 170, 522-529.
[15] Y. Zhu, M. Chen, Q. Li, C. Yuan, C. Wang, Carbon 2017, 123, 727-734.
[16] X. Xu, C. M. Friend, J. Phys. Chem. 1989, 93, 8072–8080.
[17] D. C. J. V. Salyn, D. C. E. K. Žumadilov, D. V. I. Nefedov, D. C. R. Scheibe,
D. G. Leonhardt, D. L. Beyer, P. D. E. Hoyer, Z. anorg. allg. Chem. 1977,
432, 275-279.
[18] B. Lindberg, A. Berndtsson, R. Nilsson, R. Nyholm, O. Exner, Acta Chem.
Scand., Ser. A 1978, 32, 353-359.
[19] G. Beamson, D. Briggs, Wiley, Chichester, J. Electron Spectrosc. Relat.
Phenom. 1992, 62, 371-372.
[20] a) T. Yoshida, S. Sawada, Bull. Chem. Soc. Jpn. 1974, 47, 50-53; b) D.
N. Hendrickson, J. M. Hollander, W. L. Jolly, Inorg. Chem. 1969, 8, 2642-
2647.
[21] J. Xu, B. Zhao, Z. Li, W. Chu, J. Mao, D. C. Olk, J. Zhang, X. Xin, W. Wei,
J. Agric. Food Chem. 2019, 67, 8107-8118.
[22] R. F. Egerton, P. Li, M. Malac, Micron 2004, 35, 399-409.
[23] J. E. Drawdy, G. B. Hoflund, S. D. Gardner, E. Yngvadottir, D. R. Schryer,
Surf. Interface Anal. 1990, 16, 369-374.
[24] Q. Liu, Z. Zhang, Catal. Sci. Technol. 2019, 9, 4821-4834.
[25] K. Itami, K. Mitsudo, A. Nishino, J.-i. Yoshida, Chem. Lett. 2001, 11,
1088-1089.
[26] X. Cui, K. Junge, X. Dai, C. Kreyenschulte, M. M. Pohl, S. Wohlrab, F.
Shi, A. Bruckner, M. Beller, ACS Cent. Sci. 2017, 3, 580-585.
[27] A. J. Chalk, J. F. Harrod, J. Am. Chem. Soc. 1965, 87, 16-21.
[28] A. J. Chalk, J. F. Harrod, Organic Synthesis via Metal Carbonyls, Vol. 2,
John Wiley & Sons Ltd, New York, 1977.
[29] T. K. Meister, K. Riener, P. Gigler, J. r. Stohrer, W. A. Herrmann, F. E.
Kꢀhn, ACS Catal. 2016, 6, 1274-1284.
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This article is protected by copyright. All rights reserved.

10.1002/anie.202109689
Angewandte Chemie International Edition
RESEARCH ARTICLE
Entry for the Table of Contents
A humic acid based carbonaceous support material AHA_U_400 was prepared through mild thermal condensation and cross-linking
between artificial humic acid and urea, and the material proved to enable the preparation of stable Pt single atom catalyst
(Pt1@AHA_U_400). Pt was coordinated to two unsaturated O atoms, as well as one Cl- and one HCl moiety. The catalyst showed
ultrahigh performance in hydrosilylation reactions with the TOF 3.0 x 107 h-1, high selectivity (>99%) and good stability during reuse.
7
This article is protected by copyright. All rights reserved.