C Catalyst Generation via

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Hydroxyl Group Regulated Active Nano-Pd/C Catalyst Generation via Insitu Reduction of Pd(NH3)xCly/C for N-Formylation of Amine with CO2/H2 Yujing Zhang, Hongli Wang, Hangkong Yuan, and Feng Shi ACS Sustainable Chem. Eng., Just Accepted Manuscript • Publication Date (Web): 01 Jun 2017 Downloaded from http://pubs.acs.org on June 2, 2017

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ACS Sustainable Chemistry & Engineering

Hydroxyl Group Regulated Active Nano-Pd/C Catalyst Generation via In-situ Reduction of Pd(NH3)xCly/C for N-Formylation of Amine with CO2/H2 Yujing Zhang,†,‡ Hongli Wang,† Hangkong Yuan† and Feng Shi†*

†

State Key Laboratory for Oxo Synthesis and Selective Oxidation, Centre for Green Chemistry

and Catalysis, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, No.18, Tianshui Middle Road, Lanzhou, 730000, China ‡

University of Chinese Academy of Sciences, No. 19A, Yuquanlu, Beijing, 100049, China

The reductive N-formylation of amines using CO2 and hydrogen is a promising means of incorporating CO2 into value-added chemicals. To date, there has been a lack of heterogeneous catalyst systems that are sufficient active and selective for N-formylation of primary amines with CO2 and H2. For the first time, we report that a highly active palladium nanoparticle supported on hydroxyl group functionalized carbon material has been designed for the N-formylation of aliphatic primary amines with CO2 and H2. XPS, XRD, FT-Raman and TEM characterizations revealed the adsorbing of Pd(NH3)xCly onto the carbon support during catalyst preparation, and followed by in-situ reduction to generate active nano-Pd particles. The catalytic activity of the

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Pd/C catalysts can be tuned efficiently by the hydroxyl group, which can modulate the hydrophilic/hydrophobic properties of the carbon surface, and promote the adsorption of CO2 and the amines near the Pd sites. The results described here may promote the design of active catalyst for CO2 recycling and N-formyl amine synthesis.

INTRODUCTION The utilization of carbon dioxide (CO2) as a feedstock for fine chemical synthesis has attracted considerable attentions due to the fact that CO2 is a cheap, renewable, abundant, and green C1 resource.1-10 In the last decades, great efforts have been devoted to explore efficient catalyst systems for CO2 conversion. Among them, the reduction of CO2 in the presence of amines is a promising pathway for the formation of N-methylamines11-24 or N-formamides, which are valueadded fine chemicals. In particular, formamide derivatives, such as N,N-dimethylformamide (DMF), are important solvents and key intermediates in the synthesis of adhesives, pesticides, and drugs and formulation of polymers25,26. More recent works have focused on development of new catalytic methodologies for the conversion of CO2 to formamides using hydrosilanes27-39 and borane15,40 as the reductants. However, in comparison with hydrosilanes and boranes, hydrogen is the cleanest, atom-economical and economic reductant. Furthermore, products are prone to isolated from the reaction mixtures when hydrogen was applied. Since the initial report by Adkins and co-workers on RANEY Ni catalyzed reductive formylation of amines with CO2 and H2,41 a series of homogeneous or heterogeneous transition-metal catalysts such as ruthenium,42-53 palladium,54,55 platinum,56 copper,57-59 Iridium,60 iron61 and others62 are developed. Although extensively studied, N-formylation of primary amines with CO2 and H2 remains a formidable challenge in this field. The pioneering work by Adkins et al. first reported


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the formylation of N-amylamine with CO2 and H2, albeit in only 45% yield.41 In 2003, Jessop et al. discovered attractive formylation of aniline with CO2 and H2 in the presence of RuCl2(PMe3)4 and a stoichiometric amount of DBU.49 In 2005, a successful formylation of 3methoxypropylamine with H2 and supercritical CO2 was achieved in the presence of ruthenium catalysts.51 In 2015, Ding and co-workers reported an elegant homogeneous ruthenium-catalyzed N-formylation of aliphatic primary amines with CO2 and H2.53 In contrast to homogeneous catalysts, the heterogeneous catalysts are easily reused and recycled. However, there have been no examples of heterogeneous catalysts46,51,55,57-59,60 for formylation of primary amines with CO2 and H2. Therefore, the discovery of heterogeneous catalyst for N-formylation of primary amines with CO2 and H2 is highly desired. It is well known that adsorption and activation of CO2 are usually the key steps of the transformation of CO2. We envisaged that surface functionalization of the support of the heterogeneous catalyst might promote the adsorption and activation of CO2. Carbon materials, including amorphous carbon, ordered meso-porous carbon, graphite/graphene (oxide) and carbon nanotubes, are widely applied in many catalytic transformations in modern organic chemistry.6365

Noteworthy, carbon material is easy to be functionalized, which provided the possibility as a

potential candidate for the preparation of functional support to promote CO2 adsorption. For example, the functionalized carbon material with hydroxyl group, which can adsorb CO2 especially when suitable amount of base was added, can be smoothly realized via oxidation.66-69 Based on our previous work,55 palladium is an active catalyst for the N-formylaton of amines with CO2 and H2. Therefore, we envisioned that hydroxyl group functionalized carbon supported nano-Pd might establish an efficient approach to realize N-formylation of primary amines with CO2 and H2. Herein a series of carbon supported nano-Pd catalysts were prepared with


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precipitation-deposition method, and the results showed that the carbon supports with higher hydroxyl group density provide better catalytic performance in the reductive N-formylation of amines with CO2 and H2.

Scheme 1. N-formylation of amines with CO2/H2 catalyzed by supported nano-palladium catalyst

EXPERIMENTAL SECTIONS All solvents and chemicals were obtained commercially and were used as received.

Figure 1. An illustration of the Pd/C catalyst preparation. Typical procedure for carbon support preparation: The carbon materials were prepared via sol-gel polymerization of resorcinol and formaldehyde with Na2CO3 as a catalyst (Figure 1).


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First, a wet RF gel was prepared by polymerization of resorcinol and formaldehyde at 80 oC using a hydrothermal method. Then, the wet RF gel was mixed with KOH or another base and heated at 800 oC under a nitrogen flow. Next the carbonized sample was washed with deionized water to remove the base, and the carbon material was obtained. A series of carbon materials was prepared using this method by varying the type of base. The carbon materials that were not treated with a base are denoted C-none. C-KOH, C-NaOH, C-K2CO3, C-Na2CO3, C-K3PO4 were prepared using various bases (that is, KOH, NaOH, K2CO3, Na2CO3, K3PO4 respectively) with a fixed ratio of wet RF gel to base (that is, 1 : 1). The oxidation process was carried out by adding 40 mL of nitric acid (14.5 M, 65% HNO3) to 4.0 g C-KOH placed in a round-bottom flask. The mixture was heated at 25 oC, 50 oC, 80 oC or 110 oC on hot plate with constant stirring for 1 h, then washed with distilled water to neutral, decanted and the solid sample was dried at 110 oC in air. The carbon materials that were not treated with a nitric acid are denoted C-0. C-1, C-2, C-3 and C-4 were prepared at different temperatures (that is 25 oC, 50 oC, 80 oC or 110 oC). Typical procedure for carbon supported nano-Pd catalyst preparation: 0.25 g C-3 and 0.08 mL H2PdCl4 (aqueous solution, 29.93 mg/mL) were added into 10 mL aqueous solution of ammonia hydroxide (1 mol/L). After further stirring for 24 h at r.t., the water was removed under vacuum. It was dried at 80 °C in air for 6 h and then reduced under hydrogen flow at 200 °C for 2 h. The resulting catalyst samples were denoted as Pd/C-3. Following, the catalysts ware characterized by BET surface-area analysis (BET), transmission electron microscopy (TEM), Xray power diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and the reaction products were characterized by nuclear magnetic resonance spectrum (NMR). XRD measurements were conducted by using a STADIP automated transmission diffractometer (STOE) equipped with an


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incident beam curved germanium monochromator with CuKa1 radiation and current of 40Kv and 150mA, respectively. The XRD patterns were scanned in the 2 Theta range of 10-80o. XPS were obtained using a VG ES-CALAB 210 instrument equipped with a dual Mg/Al anode X-ray source, a hemispherical capacitor analyzer, and a 5keVAr+ iron gun. The electron binding energy was referenced to the C1s peak at 284.8 eV. The background pressure in the chamber was less than 10-7Pa. The peaks were fitted by Gaussian–Lorentzian curves after a Shirley background subtraction. For quantitative analysis, the peak area was divided by the element-specific Scofield factor and the transmission function of the analyzer. Nitrogen adsorption–desorption isotherms were measured at 77 K by using a Quanta chrome autosorb iQ2 instrument. The pore size distribution was calculated from the desorption isotherm by using the Barrett, Joyner, and Halenda (BJH) method. Prior to measurements, the samples were degassed at 200 oC for 10 h, at a rate of 10 oC/min. TEM was carried out by using a Tecnai G2 F30 S-Twin transmission electron microscope operating at 300 kV. Single-particle EDX analysis was performed by using a Tecnai G2 F30 S-Twin Field Emission TEM in STEM mode. For TEM investigations, the catalysts were dispersed in ethanol by ultrasonication and deposited on carbon-coated copper grids. NMR spectra were measured by using a Bruker ARX 400 or ARX 100 spectrometer at 400 MHz (1H) and 100 MHz (13C). All spectras were recorded in CDCl3 and chemical shifts (d) are reported in ppm relative to tetramethylsilane referenced to the residual solvent peaks. Catalytic performance test: The catalytic activity was tested by N-formylation of piperidine as the model reaction. 1.0 mmol amines, 50 mg catalyst and 2 mL methanol were added into a 100 mL autoclave equipped with magnetic stirrer. The autoclave was sealed and exchanged with CO2 for 3 times and reacted at 105 oC (oven temperature 130 oC) under 1 MPa CO2 and 3 MPa H2 for 24 h. Then it was cooled to room temperature, and 10 mL ethanol was added, and the


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reaction mixture was analyzed by GC-MS (Agilent 7890B/5977A). The GC-yield was determined by GC-FID (Agilent 7890A) using biphenyl as internal standard, and the isolated yields were obtained by flash column chromatography.

Results and discussion Catalyst screening and reaction conditions optimization Table 1. The catalyst screening

Yield[%][b]

Entry

Sample

1

Pd/C-none

27

2

Pd/C-KOH

51

3

Pd/C-NaOH

34

4

Pd/C-K2CO3

30

5

Pd/C-Na2CO3

36

6

Pd/C-K3PO4

27

[a] Reaction conditions: 1.0 mmol piperidine, 50 mg Pd/C (1wt% Pd, 0.47 mol% Pd to 1a), 2 mL methanol, 105 oC, 0.5 mmol KOH, 1/3 MPa CO2/H2, 5 h. [b] Yield determined by gas chromatography using biphenyl as internal standard. In order to find out a suitable carbon material to check the influence of hydroxyl group on the catalytic performance of the Pd/C catalyst, first, a series of carbon materials were prepared with sol-gel polymerization and followed by carbonization with or without the addition of base. By applying these carbon supports, a series of Pd/C catalysts were prepared with precipitation-


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deposition method. The catalyst screening was performed with N-formylation of piperidine (1a) as the model reaction. The results suggested that 27% yield was obtained with Pd/C-none was used as catalyst (Table 1, entry 1). The treatment of the carbon supports can improve the catalytic performance of Pd/C remarkably, and the applying of Pd/C-KOH afforded 51% yield (Entry 2). Lower yields to N-formyl piperidine were obtained if Pd/C-NaOH, Pd/C-Na2CO3, Pd/C-K2CO3, and Pd/C-K3PO4 were used as catalysts (Entries 3-6). Therefore, C-KOH (C-0) was chosen as the standard carbon to prepare carbon materials with different hydroxyl group densities via oxidation with nitric acid at different temperatures, and C-1, C-2, C-3 and C-4 were produced via C-0 oxidation at 25-110 oC. Table 2. The catalyst screening

Yield[%][b]

Entry

Sample

1

Pd/C-0

13

2

Pd/C-1

11

3

Pd/C-2

17

4

Pd/C-3

19

5

Pd/C-4

16

Reaction conditions: 1.0 mmol piperidine, 50 mg Pd/C (1 mol% Pd), 2 mL methanol, 105 oC, 0.5 mmol KOH, 1/3 MPa CO2/H2, 2 h. Then these carbon materials were used as supports to prepare Pd/C catalysts, which were denoted as Pd/C-0, Pd/C-1, Pd/C-2, Pd/C-3 and Pd/C-4. The catalytic performance of these


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catalysts was tested (Table 2). Clearly, the highest catalytic performance was observed with Pd/C-3, providing the N-formylation product in 19% yield at 105 oC for 2 h (The oven temperature is 130 oC, while 105 oC is the actual temperature measured by thermocouple). Therefore, catalyst Pd/C-3 was used for the further optimization of the reaction conditions. Table 3. Reaction conditions optimization for N-formylation of piperidine

Entry

Catalyst

Solvent

KOH/mmol

CO2/H2(Mpa)

Yield of 1b /(%)b

1

Pd/C-3

Methanol

0

2:3

45

2

Pd/C-3

Methanol

0.3

2:3

55

3

Pd/C-3

Methanol

0.5

2:3

57

4

Pd/C-3

Methanol

1.0

2:3

60

5

Pd/C-3

Methanol

0.5

1:3

62

6

Pd/C-3

Methanol

0.5

2:2

32

7

Pd/C-3

Methanol

0.5

1:2

43

8

Pd/C-3

Methanol

0.5

1:4

57

9

Pd/C-3

C2H5OH

0.5

1:3

22

10

Pd/C-3

1,4-dioxane

0.5

1:3

17

11

Pd/C-3

CH2Cl2

0.5

1:3

2

12

Pd/C-3

H2O

0.5

1:3

0

13c

Pd/C-3

Methanol

0.5

1:3

99(93d, 82e)


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[a] Reaction conditions: 1.0 mmol amine, 50 mg catalyst (1wt% Pd, 0.47 mol% Pd to 1a), 105 oC, 5 h. [b] Determined by GC-FID using biphenyl as the standard material. [c] 24 h. [d] Isolated yield. [e] The catalyst was recovered and reused at the 3rd run. Following, the influence of base on the catalytic reaction was evaluated. Clearly the results can be improved slightly if KOH was added during the reactions (Table 3, entries 1-4). As similar results were obtained when 50% or 100% KOH was added, finally we chose 50% KOH as additive for further improvement. Then the influence of solvents, i.e., MeOH, EtOH, 1,4Dioxane, CH2Cl2 and H2O, and the CO2/H2 ratios were tested, and the best result was obtained when 50% KOH was added with a CO2/H2 ratio of 1 : 3, and methanol as solvent (Entries 5-12). Finally, 99% GC yield to N-formyl piperidine was achieved if prolonging the reaction time to 24 h, and the isolated yield was 93% (Table 2, entry 13). Pd(NO3)2 was used to instead of H2PdCl4 to prepare catalyst Pd/C-3, and the yield of N-formyl piperidine was 88% when it was applied in the piperidine N-formylation reaction, which indicated the anion of the Pd precursor influences the catalytic performance of the final catalyst sample less. Also, this catalyst is easily recoverable by simple filtration, and it can be used directly without further treatment. To our delight, 82% yield was maintained when it was used at 3rd run thus this catalyst exhibits nice reusability. Catalyst Characterization


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Figure 2. Contents of surface oxygenated groups by Boehm Titration In order to prove that catalytic activity was influenced by hydroxyl group density, Boehm Titration analysis was performed to determine contents of surface oxygenated groups (Figure 2). The content of surface number of phenol groups first dropped from 208 µmol/g to 119 µmol/g, then increased from 119 µmol/g to 808 µmol/g (Table S1). The same trend was observed in Lactone groups (Table S1). However, the content of surface number of carboxylic acid groups continuously increased from 0 µmol/g to 2599 µmol/g (Table S1). With the increasing of hydroxyl group density, the yield for N-formyl piperidine was improved to 19% yield when Pd/C-3 was used as the catalyst (Table 2, entry 4). It is similar to the trend of surface number content of phenol and lactone groups. Given the lactone groups are weak for the adsorption of CO2. Therefore, we supposed that phenol groups belonging to the support influenced the catalytic activity of the catalyst. However, the yield for N-formyl piperidine was decreased to 16% if the hydroxyl group density was further increased (Table 2, entry 5). It was well-known that the treatment of carbon material at elevated temperature would cause collapse of its framework. We reasoned that decreasing of the catalytic activity might result from collapse of carbon material framework. Table 4. The physicochemical properties of catalysts Different catalysts

SBET(m2/g)

Vpa(cm3/g)

Dpb(nm)

Pd/C-0

744

0.44

1.18

Pd/C-1

875

0.46

1.04

Pd/C-2

878

0.48

1.09

Pd/C-3

702

0.40

1.14

Pd/C-4

202

0.20

1.94


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[a] Pore volume measured at the single point of P/P0 = 0.99. [b] BJH desorption average pore diamete. So these carbon materials were characterized by BET surface-area analysis (BET) (Table 4). The results of BET analysis confirmed our conjecture, and the BET surface areas dropped remarkably from 702-878 m2/g to 202 m2/g. This might be the main reason for the decreasing of the catalytic activity when it was applied as the catalyst support. The N2 adsorption/desorption isotherm exhibited a steep increase (Fig. S2), signifying the presence of microporosity with a pore size distribution at 0.2-0.3 nm. The Barret–Joyner–Halenda (BJH) pore size distribution further revealed the mean size of mesopores to be 2-3 nm. Given the size of amines molecular is usually larger than the microporous size, the nano-Pd particles located inside mesopores or on the support surface might play a key role in N-formylation of the amines with CO2/H2. In order to reveal the structure of the Pd/C catalysts, they were further characterized by XRD, XPS, FT-Raman, and TEM. First, the catalysts were characterized by XRD (Figure 3a and Fig. S 8), and there are no observable diffraction patterns of Pd species, which suggested that the Pd species were amorphous or highly dispersed. The Pd 3d5/2 peak at 335.9 eV is attributed to Pd0 (metallic palladium), while the Pd 3d5/2 peak at 337.5 eV is related to Pd2+ (palladium oxide or Pd(NH3)xCly). According to XPS data, Pd2+ was mainly formed on the surface of the fresh catalyst and Pd0 was almost not formed (Figure 4 and Fig. S6). The same results are afforded in the XPS spectra of the Pd/C-3 which was submitted to CO2 + H2 before collecting the spectra (Fig. S6). The possibility of surface oxidation by air was ruled out. We wonder whether Pd2+ can be active for the reductive formylation of the amines with CO2 and H2. So the catalyst sample used three times was characterized by XPS and the formation of Pd0 (metallic palladium) on the carbon surface was observed, which indicated in-situ formation of active Pd0 species during the


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reaction process. In addition, XPS spectra suggested that small amount of K cation was retained into the catalyst and the K/C atomic ratio had not obvious impact on the reactivity as below. Clearly, there is no relationship between the catalytic results and K cation inside the catalyst sample. In order to verify the real palladium species in catalyst Pd/C-3, it was further characterized by FT-Raman (Figure 3b and Fig. S10), which revealed that Pd(NH3)xCly but not Pd2+ was mainly formed on the surface of the fresh catalyst.70 The HR-TEM image shown in (Figure 5 and Fig. S4) confirms the observations from the XPS spectra and FT-Raman spectra. The crystal lattices of fresh catalyst was Pd(NH3)xCly, and the crystal lattices of catalyst sample used three times was Pd0 species. The TEM images showed that 63% Pd species in Pd/C-3 was in the range of 0 to 1 nm, while it was mainly 1-4 nm in other catalysts. It should be noted that 86% of Pd species dropped in the range of 0 to 1 nm after Pd/C-3 being used for three times. All these results clearly indicate that the fresh catalysts contain Pd(NH3)xCly immobilized on the surface of functional carbon-base materials, and the active nano-Pd was generated in-situ during the reaction.

a

b

Figure 3. (a) XRD diffraction patterns of catalyst, (b) Raman pictures of catalyst.


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Figure 4. XPS spectra of fresh catalyst (left) and used three times catalyst (right).

Figure 5. (a) TEM images of fresh catalyst, (b) HADDF-STEM images and particle size distributions of fresh catalyst, (c) TEM images of used three times catalyst, (d) HADDF-STEM images and particle size distributions of used three times catalyst. In addition, CO2/NH3-TPD characterizations were performed (Fig. S11 and 12). Unfortunately, only less difference can be observed from the results of different samples. So the correlations between catalytic activity and whole acidic/basic groups on the catalyst surfaces can not be built. Therefore, the –OH groups might be helpful to modulate the hydrophilic/hydrophobic properties of the carbon surface, which can favor the adsorption of CO2 and the amines near the Pd sites, because no important change of the density of acid and basic sites is observed as a function of


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the preparation method. CO2 adsorption tests with FT-IR suggested that other peaks of CO2 adsorption were not observed in addition to background peaks (Fig. S13). With the optimized conditions in hand, the scope of this Pd/C-3 catalyzed N-formylation of different secondary amines was further investigated, and the results were summarized in Table 5. By using substituted piperidines as substrates, the reaction proceeded successfully and furnished the desired products in 65–93% yields (2a-2d). In addition, other cyclic secondary amines, such as piperazine and morpholine, were also converted into the formamides in 68-89% yields under the optimized conditions (2e-2h). Moreover, pyrrolidine and 1,2,3,4-tetrahydroisoquinoline were converted into the corresponding formamides smoothly in 81% and 83% yields, respectively. The employment of other dialkyalmines, such as Me2NH, n-Pr2NH, and Oct2NH, led to good yields, too (2j-2l). Table 5. Results of N-formylation of secondary amines[a] Entry

subsates

Product

1

Yield(%)

93 1a

2a

2

65 1b

2b

73

3 1c

2c


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O N

H

4

84 1d

2d

5

69 1e

2e

6

78 1f

2f

7

68 1g

2g O NH

N

O

H

O

8 1h

89

2h

83

9 1i

2i O N

10 1j

53

2j

11b

76


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1k

2k

12b

71 1l

2l

82

13 1m

2m

14

71 1n

2n

[a] Reaction conditions: 1.0 mmol amine, 50 mg catalyst (1wt% Pd, 0.47 mol% Pd to 1), 2 mL MeOH, 105 oC, 24 h. [b] 36 h. Inspired by the results in Table 4, N-formylation of primary amines was further investigated (Table 6). It should be mentioned that primary aliphatic amines with different alkyl chain proceeded well, affording their corresponding products in moderate yields. The steric hindrance substrate 1u was also worked to provide 2u in 74% yield. It is noteworthy that when benzylamine 1w and amphetamine 1x, bearing benzene ring on the substrates, can also be converted into desired products of 2w and 2x in 91% and 92% yields, respectively. Table 6. Results of N-formylation of primary amines[a] Entry

Substrates

Products

1

Yields[c]

77 1o

2o

2

82 1p


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2p

3

88 1q

2q

4

95 1r

2r

5

83 1s

2s

81

6 1t

2t

7

74 1u

2u

78

8 1v

2v

9

91 1w

2w

92

10 1x

2x

[a] Reaction conditions: 1.0 mmol amine, 50 mg catalyst (1wt% Pd, 0.47 mol% Pd to 1), 2 mL MeOH, 105 oC, 24 h.


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When aniline was subjected to this reductive formylation protocol (Scheme 2), 49% conversion of aniline with 27% of N-formanilide, 6% N-Cyclohexylformamide selectivities was obtained. These result indicated that in order to achieve the N-formylation of the aromatic amines, we should design a catalyst with nice catalytic performance in the reduction of CO2 while is resistant to hydrogenate the aromatic rings. H N

NH2

+ CO2/H2 1.0 mmol (4/2 MPa) Conv: 49%

40 mg Pd/C-3 0.5 equiv.KOH CH3OH, 125

oC,

15 h

H N

+

H N

+

O

O

Sel: 10% H N

Sel: 27% +

Sel: 21%

Sel: 6% H N

Sel: 36%

Scheme 2. N-formylation of aniline with CO2/H2 To obtain insights into the mechanism of the N-formylation reaction, control experiment was performed. Reaction of pepridine with CO2 was performed in the presence of 50 mg Pd/C-3 in methanol at 105 °C for 2 h under 10 atm CO2 without the addition of H2. After the reaction mixtures were centrifuged and washed with methanol, the catalyst was further reacted in methanol at 105 °C for 5 h under 10 atm H2 and 20 atm N2, which afford desired formylation product in 0.9% yield with recovery of 1.4% pepridine. These results suggest that this Nformylation first reaction of amine with CO2 in the presence of the Pd/C-3 and KOH to form the carbamate followed by hydrogenation to form the formylation product.

Scheme 3. Control experiment for mechanism study


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Conclusions In conclusion, an active catalyst can be obtained for the N-formylation of amines with CO2 and H2 by immobilizing nano-Pd onto the hydroxyl group functionalized carbon materials. The active nano-Pd/C structure was generated in-situ from Pd(NH3)xCly/C during the reaction. In the presence of this catalyst, the N-formylation of a variety of amines, especially primary aliphatic amines can be achieved under relatively mild conditions. The hydroxyl group on the carbon surface might be helpful to modulate hydrophilic/hydrophobic properties of the carbon surface, and promote the adsorption of CO2 and the amines near the Pd sites. Further development of Nformylation of aromatic amines is underway in our laboratory. ASSOCIATED CONTENT Supporting Information. The Supporting Information is available free of charge on the ACS Publications website. The characterization results of the catalysts and isolated products were provided. AUTHOR INFORMATION Corresponding Author *[email protected]. Author Contributions F. Shi supervised the research work, Y. Zhang performed the reactions, Y. Zhang, H. Wang, H. Yuan and F. Shi analyzed the data and wrote the manuscript.

ACKNOWLEDGMENT We thank the National Natural Science Foundation of China (21633013). REFERENCES


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(1) Sakakura, T.; Choi, J.-C.; Yasuda, H. Transformation of Carbon Dioxide. Chem. Rev. 2007, 107 (6), 2365-2387. (2) Huang, K.; Sun, C.-L.; Shi, Z.-J. Transition-Metal-Catalyzed C-C Bond Formation through the Fixation of Carbon Dioxide. Chem. Soc. Rev. 2011, 40 (5), 2435-2452. (3) Wang, W.; Wang, S.; Ma, X.; Gong, J. Recent Advances in Catalytic Hydrogenation of Carbon Dioxide. Chem. Soc. Rev. 2011, 40 (7), 3703-3727. (4) Aresta, M.; Dibenedetto, A.; Angelini, A. Catalysis for the Valorization of Exhaust Carbon: From Co2 to Chemicals, Materials, and Fuels. Technological Use of CO2. Chem. Rev. 2013, 114 (3), 1709-1742. (5) Bhanage, B. M. Transformation and utilization of carbon dioxide; Springer, 2014. (6) Li, Y.; Chan, S. H.; Sun, Q. Heterogeneous Catalytic Conversion of CO2: A Comprehensive Theoretical Review. Nanoscale 2015, 7 (19), 8663-8683. (7) Liu, Q.; Wu, L.; Jackstell, R.; Beller, M. Using Carbon Dioxide as a Building Block in Organic Synthesis. Nat. Commun. 2015, 6. (8) Lu, X.-B. Carbon Dioxide and Organometallics; Springer, 2015; Vol. 53. (9) Shi, J.; Jiang, Y.; Jiang, Z.; Wang, X.; Wang, X.; Zhang, S.; Han, P.; Yang, C. Enzymatic Conversion of Carbon Dioxide. Chem. Soc. Rev. 2015, 44 (17), 5981-6000. (10) Klankermayer, J.; Wesselbaum, S.; Beydoun, K.; Leitner, W. Selective Catalytic Synthesis Using the Combination of Carbon Dioxide and Hydrogen: Catalytic Chess at the Interface of Energy and Chemistry. Angew. Chem. Int. Ed. 2016, 55 (26), 7296-7343. (11) Beydoun, K.; vom Stein, T.; Klankermayer, J.; Leitner, W. Ruthenium-Catalyzed Direct Methylation of Primary and Secondary Aromatic Amines Using Carbon Dioxide and Molecular Hydrogen. Angew. Chem. Int. Ed. 2013, 52 (36), 9554-9557. (12) Jacquet, O.; Frogneux, X.; Gomes, C. D. N.; Cantat, T. CO2 as a C1-Building Block for the Catalytic Methylation of Amines. Chem. Sci. 2013, 4 (5), 2127-2131. (13) Li, Y.; Fang, X.; Junge, K.; Beller, M. A General Catalytic Methylation of Amines Using Carbon Dioxide. Angew. Chem. Int. Ed. 2013, 52 (36), 9568-9571. (14) Li, Y.; Sorribes, I.; Yan, T.; Junge, K.; Beller, M. Selective Methylation of Amines with Carbon Dioxide and H2. Angew. Chem. Int. Ed. 2013, 52(46), 12156-12160. (15) Blondiaux, E.; Pouessel, J.; Cantat, T. Carbon Dioxide Reduction to Methylamines under Metal‐Free Conditions. Angew. Chem. Int. Ed. 2014, 53 (45), 12186-12190. (16) Cui, X.; Dai, X.; Zhang, Y.; Deng, Y.; Shi, F. Methylation of Amines, Nitrobenzenes and Aromatic Nitriles with Carbon Dioxide and Molecular Hydrogen. Chem. Sci. 2014, 5 (2), 649655. (17) Cui, X.; Zhang, Y.; Deng, Y.; Shi, F. N-Methylation of Amine and Nitro Compounds with CO2/H2 Catalyzed by Pd/CuZrOX under Mild Reaction Conditions. Chem. Commun. 2014, 50 (88), 13521-13524. (18) Das, S.; Bobbink, F. D.; Laurenczy, G.; Dyson, P. J. Metal-Free Catalyst for the Chemoselective Methylation of Amines Using Carbon Dioxide as a Carbon Source. Angew. Chem. Int. Ed. 2014, 53 (47), 12876-12879. (19) Kon, K.; Siddiki, S.; Onodera, W.; Shimizu, K. i. Sustainable Heterogeneous Platinum Catalyst for Direct Methylation of Secondary Amines by Carbon Dioxide and Hydrogen. Chem. Eur. J. 2014, 20 (21), 6264-6267. (20) Catherine, S. N-Heterocyclic Carbene Copper(I) Catalysed N-Methylation of Amines Using CO2. Dalton Trans. 2015, 44 (41), 18138-18144.


21


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 22 of 26

(21) Chen, W. C.; Shen, J. S.; Jurca, T.; Peng, C. J.; Lin, Y. H.; Wang, Y. P.; Shih, W. C.; Yap, G.; Ong, T. G. Expanding the Ligand Framework Diversity of Carbodicarbenes and Direct Detection of Boron Activation in the Methylation of Amines with CO2. Angew. Chem. Int. Ed. 2015, 54 (50), 15207-15212. (22) Tang, G.; Bao, H.-L.; Jin, C.; Zhong, X.-H.; Du, X.-L. Direct Methylation of NMethylaniline with CO2/H2 Catalyzed by Gold Nanoparticles Supported on Alumina. RSC Adv. 2015, 5 (121), 99678-99687. (23) Yang, Z.; Yu, B.; Zhang, H.; Zhao, Y.; Ji, G.; Ma, Z.; Gao, X.; Liu, Z. B(C6F5)3-Catalyzed Methylation of Amines Using CO2 as a C1 Building Block. Green Chem. 2015, 17 (8), 41894193. (24) Beydoun, K.; Thenert, K.; Streng, E. S.; Brosinski, S.; Leitner, W.; Klankermayer, J. Selective Synthesis of Trimethylamine by Catalytic N-Methylation of Ammonia and Ammonium Chloride by Utilizing Carbon Dioxide and Molecular Hydrogen. ChemCatChem 2016, 8 (1), 135-138. (25) Bipp, H.; Kieczka, H. Formamides. Ullmann's encyclopedia of industrial chemistry 2000. (26) Arpe, H.-J.; Weissermel, K. Industrial Organic Chemistry; Wiley-VCH Weinheim, 2010; Vol. 393. (27) Das Neves Gomes, C.; Jacquet, O.; Villiers, C.; Thuéry, P.; Ephritikhine, M.; Cantat, T. A Diagonal Approach to Chemical Recycling of Carbon Dioxide: Organocatalytic Transformation for the Reductive Functionalization of CO2. Angew. Chem. Int. Ed. 2012, 51 (1), 187-190. (28) Jacquet, O.; Das Neves Gomes, C.; Ephritikhine, M.; Cantat, T. Recycling of Carbon and Silicon Wastes: Room Temperature Formylation of N-H Bonds Using Carbon Dioxide and Polymethylhydrosiloxane. J. Am. Chem. Soc. 2012, 134 (6), 2934-2937. (29) González-Sebastián, L.; Flores-Alamo, M.; Garcı́a, J. J. Nickel-Catalyzed Hydrosilylation of CO2 in the Presence of Et3B for the Synthesis of Formic Acid and Related Formates. Organometallics 2013, 32 (23), 7186-7194. (30) Itagaki, S.; Yamaguchi, K.; Mizuno, N. Catalytic Synthesis of Silyl Formates with 1Atm of CO2 and Their Utilization for Synthesis of Formyl Compounds and Formic Acid. J. Mol. Catal. A: Chem. 2013, 366, 347-352. (31) Motokura, K.; Takahashi, N.; Kashiwame, D.; Yamaguchi, S.; Miyaji, A.; Baba, T. CopperDiphosphine Complex Catalysts for N-Formylation of Amines under 1 Atm of Carbon Dioxide with Polymethylhydrosiloxane. Catal. Sci. Technol. 2013, 3 (9), 2392-2396. (32) Frogneux, X.; Jacquet, O.; Cantat, T. Iron-Catalyzed Hydrosilylation of CO2 : CO2 Conversion to Formamides and Methylamines. Catal. Sci. Technol. 2014, 4 (6), 1529-1533. (33) Motokura, K.; Takahashi, N.; Miyaji, A.; Sakamoto, Y.; Yamaguchi, S.; Baba, T. Mechanistic Studies on the N-Formylation of Amines with CO2 and Hydrosilane Catalyzed by a Cu-Diphosphine Complex. Tetrahedron 2014, 70 (39), 6951-6956. (34) Chong, C. C.; Kinjo, R. Hydrophosphination of CO2 and Subsequent Formate Transfer in the 1,3,2-Diazaphospholene-Catalyzed N-Formylation of Amines. Angew. Chem. Int. Ed. 2015, 54 (41), 12116-12120. (35) Hao, L.; Zhao, Y.; Yu, B.; Yang, Z.; Zhang, H.; Han, B.; Gao, X.; Liu, Z. ImidazoliumBased Ionic Liquids Catalyzed Formylation of Amines Using Carbon Dioxide and Phenylsilane at Room Temperature. ACS Catal. 2015, 5 (9), 4989-4993. (36) Nguyen, T. V.; Yoo, W. J.; Kobayashi, S. Effective Formylation of Amines with Carbon Dioxide and Diphenylsilane Catalyzed by Chelating Bis(tzNHC) Rhodium Complexes. Angew. Chem. Int. Ed. 2015, 54 (32), 9209-9212.


22

Page 23 of 26

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(37) Das, S.; Bobbink, F. D.; Bulut, S.; Soudani, M.; Dyson, P. J. Thiazolium Carbene Catalysts for the Fixation of CO2 onto Amines. Chem. Commun. 2016, 52 (12), 2497-2500. (38) Fang, C.; Lu, C.; Liu, M.; Zhu, Y.; Fu, Y.; Lin, B.-L. Selective Formylation and Methylation of Amines Using Carbon Dioxide and Hydrosilane Catalyzed by Alkali-Metal Carbonates. ACS Catal. 2016, 6 (11), 7876-7881. (39) Lv, H.; Xing, Q.; Yue, C.; Lei, Z.; Li, F. Solvent-Promoted Catalyst-Free N-Formylation of Amines Using Carbon Dioxide under Ambient Conditions. Chem. Commun. 2016, 52 (39), 6545-6548. (40) Shintani, R.; Nozaki, K. Copper-Catalyzed Hydroboration of Carbon Dioxide. Organometallics 2013, 32 (8), 2459-2462. (41) Farlow, M. W.; Adkins, H. The Hydrogenation of Carbon Dioxide and a Correction of the Reported Synthesis of Urethans. J. Am. Chem. Soc. 1935, 57 (11), 2222-2223. (42) Haynes, P.; Slaugh, L. H.; Kohnle, J. F. Formamides from Carbon Dioxide, Amines and Hydrogen in the Presence of Metal Complexes. Tetrahedron Lett. 1970, 11 (5), 365-368. (43) Jessop, P. G.; Hsiao, Y.; Ikariya, T.; Noyori, R. Catalytic Production of Dimethylformamide from Supercritical Carbon Dioxide. J. Am. Chem. Soc. 1994, 116 (19), 8851-8852. (44) Jessop, P. G.; Hsiao, Y.; Ikariya, T.; Noyori, R. Homogeneous Catalysis in Supercritical Fluids: Hydrogenation of Supercritical Carbon Dioxide to Formic Acid, Alkyl Formates, and Formamides. J. Am. Chem. Soc. 1996, 118 (2), 344-355. (45) Kröcher, O.; Köppel, R. A.; Baiker, A. Highly Active Ruthenium Complexes with Bidentate Phosphine Ligands for the Solvent-Free Catalytic Synthesis of N,N-Dimethylformamide and Methyl Formate. Chem. Commun. 1997, (5), 453-454. (46) Schmid, L.; Rohr, M.; Baiker, A. A Mesoporous Ruthenium Silica Hybrid Aerogel with Outstanding Catalytic Properties in the Synthesis of N,N-Diethylformamide from CO2, H2 and Diethylamine. Chem. Commun. 1999, (22), 2303-2304. (47) Liu, F.; Abrams, M. B.; Baker, R. T.; Tumas, W. Phase-Separable Catalysis Using Room Temperature Ionic Liquids and Supercritical Carbon Dioxide. Chem. Commun. 2001, (5), 433434. (48) Kayaki, Y.; Shimokawatoko, Y.; Ikariya, T. Amphiphilic Resin-Supported Ruthenium (II) Complexes as Recyclable Catalysts for the Hydrogenation of Supercritical Carbon Dioxide. Adv. Synth. Catal. 2003, 345 (1-2), 175-179. (49) Munshi, P.; Heldebrant, D. J.; McKoon, E. P.; Kelly, P. A.; Tai, C.-C.; Jessop, P. G. Formanilide and Carbanilide from Aniline and Carbon Dioxide. Tetrahedron Lett. 2003, 44 (13), 2725-2727. (50) Schmid, L.; Schneider, M. S.; Engel, D.; Baiker, A. Formylation with “Supercritical” CO2 : Efficient Ruthenium-Catalyzed Synthesis of N-Formylmorpholine. Catal. Lett. 2003, 88 (3), 105-113. (51) Rohr, M.; Grunwaldt, J.-D.; Baiker, A. A Simple Route to Highly Active Ruthenium Catalysts for Formylation Reactions with Hydrogen and Carbon Dioxide. J. Mol. Catal. A: Chem. 2005, 226 (2), 253-257. (52) Rezayee, N. M.; Huff, C. A.; Sanford, M. S. Tandem Amine and Ruthenium-Catalyzed Hydrogenation of CO2 to Methanol. J. Am. Chem. Soc. 2015, 137 (3), 1028-1031. (53) Zhang, L.; Han, Z.; Zhao, X.; Wang, Z.; Ding, K. Highly Efficient Ruthenium-Catalyzed N ‐Formylation of Amines with H2 and CO2. Angew. Chem. Int. Ed. 2015, 54 (21), 6186-6189.


23


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 24 of 26

(54) Kudo, K.; Phala, H.; Sugita, N.; Takezaki, Y. Synthesis of Dimethyl Formamide from Carbon Dioxide, Hydrogen and Dimethyl Amine Catalyzed by Palladium (II) Chloride. Chem. Lett. 1977, 6 (12), 1495-1496. (55) Cui, X.; Zhang, Y.; Deng, Y.; Shi, F. Amine Formylation Via Carbon Dioxide Recycling Catalyzed by a Simple and Efficient Heterogeneous Palladium Catalyst. Chem. Commun. 2014, 50 (2), 189-191. (56) Schreiner, S.; James, Y. Y.; Vaska, L. Reversible Homogeneous Catalysis of Carbon Dioxide Hydrogenation/Reduction at Room Temperature and Low Pressures. J. Chem. Soc., Chem. Commun. 1988, (9), 602-603. (57) Auer, S. M.; Gredig, S. V.; Köppel, R. A.; Baiker, A. Synthesis of Methylamines from CO2, H2 and NH3 over Cu-Mg-Al Mixed Oxides. J. Mol. Catal. A: Chem. 1999, 141 (1), 193-203. (58) Liu, J.; Guo, C.; Zhang, Z.; Jiang, T.; Liu, H.; Song, J.; Fan, H.; Han, B. Synthesis of Dimethylformamide from CO2, H2 and Dimethylamine over Cu/ZnO. Chem. Commun. 2010, 46 (31), 5770-5772. (59) Kumar, S.; Jain, S. L. An Efficient Copper Catalyzed Formylation of Amines Utilizing CO2 and Hydrogen. RSC Adv. 2014, 4 (109), 64277-64279. (60) Bi, Q.-Y.; Lin, J.-D.; Liu, Y.-M.; Xie, S.-H.; He, H.-Y.; Cao, Y. Partially Reduced Iridium Oxide Clusters Dispersed on Titania as Efficient Catalysts for Facile Synthesis of Dimethylformamide from CO2, H2 and Dimethylamine. Chem. Commun. 2014, 50 (65), 91389140. (61) Federsel, C.; Boddien, A.; Jackstell, R.; Jennerjahn, R.; Dyson, P. J.; Scopelliti, R.; Laurenczy, G.; Beller, M. A Well-Defined Iron Catalyst for the Reduction of Bicarbonates and Carbon Dioxide to Formates, Alkyl Formates, and Formamides. Angew. Chem. Int. Ed. 2010, 49 (50), 9777-9780. (62) Minato, M.; Zhou, D.-Y.; Sumiura, K.-i.; Hirabayashi, R.; Yamaguchi, Y.; Ito, T. Reactions of Quadruply Chelated Silyl- and Germyl-Molybdenum Hydrido Complexes with Carboxylic Acids and Carbon Dioxide: A First Example of Carbon Dioxide Fixation Utilizing the Trans Effect of a Silyl Ligand. Chem. Commun. 2001, (24), 2654-2655. (63) Haag, D.; Kung, H. H. Metal Free Graphene Based Catalysts: A Review. Top. Catal. 2014, 57 (6-9), 762-773. (64) Kong, X.-K.; Chen, C.-L.; Chen, Q.-W. Doped Graphene for Metal-Free Catalysis. Chem. Soc. Rev. 2014, 43 (8), 2841-2857. (65) Shearer, C. J.; Cherevan, A.; Eder, D. Application and Future Challenges of Functional Nanocarbon Hybrids. Adv. Mater. 2014, 26 (15), 2295-2318. (66) Zhang, J.; Liu, X.; Blume, R.; Zhang, A.; Schlögl, R.; Su, D. S. Surface-Modified Carbon Nanotubes Catalyze Oxidative Dehydrogenation of N-Butane. Science 2008, 322 (5898), 73-77. (67) Su, D. S.; Zhang, J.; Frank, B.; Thomas, A.; Wang, X.; Paraknowitsch, J.; Schlögl, R. Metal-Free Heterogeneous Catalysis for Sustainable Chemistry. ChemSusChem 2010, 3 (2), 169180. (68) Edwards, E.; Antunes, E.; Botelho, E. C.; Baldan, M.; Corat, E. Evaluation of Residual Iron in Carbon Nanotubes Purified by Acid Treatments. Appl. Surf. Sci. 2011, 258 (2), 641-648. (69) Wen, G.; Diao, J.; Wu, S.; Yang, W.; Schlögl, R.; Su, D. S. Acid Properties of Nanocarbons and Their Application in Oxidative Dehydrogenation. ACS Catal. 2015, 5 (6), 3600-3608. (70) Degen, I.; Rowlands, A. The Fourier Transform Raman Spectra of a Series of Platinum (II), Palladium (II) and Gold (III) Square-Planar Complexes. Spectrochim. Acta 1991, 47 (9-10), 1263-1268.


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For Table of Contents Use Only Hydroxyl Group Regulated Active Nano-Pd/C Catalyst Generation via In-situ Reduction of Pd(NH3)xCly/C for N-Formylation of Amine with CO2/H2 Yujing Zhang, Hongli Wang, Hangkong Yuan and Feng Shi*


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The N-formylation of secondary amines and aliphatic primary amines with CO2/H2 was reported with Pd/C as catalyst. It applies a sustainable methodology for N-formylation of amines.


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C Catalyst Generation via

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