A Hypercrosslin,ed Porous Porphyrin Aluminum(III) - ACS Publications

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Functional Nanostructured Materials (including low-D carbon)

A Hypercrosslinked Porous Porphyrin Aluminum(III) Tetracarbonylcobaltate as a Highly Active Heterogeneous Bimetallic Catalyst for the Ring-Expansion Carbonylation of Epoxides Vinothkumar Ganesan, and Sungho Yoon ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.9b02468 • Publication Date (Web): 30 Apr 2019 Downloaded from http://pubs.acs.org on April 30, 2019

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ACS Applied Materials & Interfaces

A Hypercrosslinked Porous Porphyrin Aluminum(III) Tetracarbonylcobaltate as a Highly Active Heterogeneous Bimetallic Catalyst for the Ring-Expansion Carbonylation of Epoxides Vinothkumar Ganesan and Sungho Yoon* Department of Applied Chemistry, College of Science and Technology, Kookmin University, 861-1, Jeongneung-dong, Seongbuk-gu, Seoul 02707, Republic of Korea KEYWORDS: hypercrosslinked polymers, heterogeneous catalysis, porphyrinoids, lactones, ring expansion carbonylations ABSTRACT: Development of an industrially viable catalyst for the ring expansion carbonylation of epoxides remains challenging in view of facile product separation and recyclability.

Herein,

we

report

a

heterogenized

porous

porphyrin

Al(III)

tetracarbonylcobaltate bimetallic catalyst for the ring-expansion carbonylation of epoxides. The catalyst was synthesized using a hypercrosslinking strategy involving methylene bridges introduced by the Friedel–Crafts reaction and incorporated with cobaltate anions. The catalyst effectively converts epoxides into the corresponding -lactones with the excellent site time yield of 360 h: , which is comparable to those of corresponding homogeneous catalysts and the highest of any heterogeneous catalyst reported so far for this reaction.

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1. INTRODUCTION -lactones are a class of strained four-membered heterocycles with widespread importance in the chemical industry owing to their application as critical intermediates in the production of compounds such as poly( -hydroxyalkanoates), which are important biodegradable polyesters,1-3 -hydroxy acids,4-5 succinic anhydrides,6 and acrylic acids.7-8 In recent years, ring-expansion carbonylation of epoxides has emerged as a convenient, direct, and atom economic method for the production of -lactones.9-14 Furthermore, this synthetic strategy allows the value-added utilization of the inexpensive C1 resource CO and epoxides, both of which can be commercially produced by a variety of practical methods and are thus readily available.15-16 The [Co(CO)4]: catalyzed ring-expansion carbonylation of epoxides to lactones has been known for several decades.17-19 Furthermore, Coates et al. reported a series of welldefined

homogeneous

bimetallic

Lewis

:

pair

catalysts,

i.e.,

([Lewis

acid]+[Co(CO)4]:), for the ring-expansion carbonylation of epoxides and proposed the catalytic mechanism shown in Scheme 1.20-24 The mechanism involves (i) epoxide activation by a Lewis-acidic metal ion; (ii) ring opening by a Lewis-basic Co(CO)4- ion; (iii) CO insertion into a Co-alkyl bond; and (iv) ring closure to generate the lactone.23 Among the ([Lewis acid]+[Co(CO)4]–)-type systems, porphyrin-based catalytic systems have proved to be the most efficient to date, even though they have limitations in terms of tedious product separation and catalyst recycling, both of which are critical for commercial-scale applicability.25-26


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O

O

[LnM]+[Co(CO)4]-

O

R

R [LnM]+[Co(CO)4]Ln M

O

R

O

O Co(CO)4

CO

LnM O

R

Co(CO)4

R -R = H, CH3, Et, n-Bu, CH2Ar etc.,

LnM - Lewis Acid

Scheme 1. Catalytic mechanism of ring-expansion carbonylation There are scattered reports of heterogeneous catalysts for the ring-expansion carbonylation of epoxides, including [bpy-CTF-Al(OTf)2]+[Co(CO)4]-, a bipyridine-based covalent triazine framework. However, the activity of this catalyst is limited to a total turnover number (TON) of 30.27 Another heterogeneous system, [Cr-metallated porous porphyrin polymer]+[Co(CO)4]-, has been reported to exhibit an improved TON of 410.28 Recently, Roman-Leshkov et al. reported [Co(CO)4]--incorporating Cr-MIL-101, a metalorganic framework, for the carbonylation of epoxides by both batch and continuous flow methods, with the significantly improved site time yield (STY) of 180 h: .29-30 However, these heterogeneous catalysts have significantly poorer activities than homogeneous systems and are difficult to prepare, making them unviable as industrial catalytic systems.27, 29-30 Thus, the development of an effective heterogeneous catalytic system with a comparable activity to those of currently employed homogeneous systems is highly desired. To that end, the direct heterogenization of a highly active homogeneous system would be an easy and attractive strategy if the development of a simple, robust, and inexpensive method of heterogenization could be achieved. Various synthetic strategies can be used to directly heterogenize active 3 ACS Paragon Plus Environment


homogeneous catalytic systems.31-36 Accordingly, knitting together the aromatic rings of homogeneous catalysts with covalent linkages using Friedel–Crafts reactions has garnered extensive research attention as it is a simple and low-cost method for generating highly porous and robust solid networks.37 In the current study, our strategy was to employ an active homogeneous catalyst as the constituent monomer in the construction of a highly porous hypercrosslinked polymer by simple solvent knitting to prepare a novel heterogeneous catalyst for the ring-expansion carbonylation of epoxides.38 We reasoned that, In this way, a heterogenized porous solid catalyst with the combined advantages of homogeneous-catalystlike activity and heterogeneous characteristics could be obtained. Considering the superior carbonylation activity of the [(TPP)Al(THF)2]+[Co(CO)4]: system and the fact that it contains four linkable aryl groups,39 we utilized meso-tetraphenylporphyrin Al(III)Cl ((TPP)AlCl, 1) as the building block in the construction of the hypercrosslinked polymer HCP-(TPP)AlCl (2) with inherent porosity and single-site catalytic centers through a one-pot Friedel–Crafts reaction (Scheme 2). Subsequently, the labile Cl- anions in polymer 2 can be exchanged with Co(CO)4– anions to generate the novel, recyclable, and efficient heterogeneous catalyst [HCP-(TPP)Al][Co(CO)4] (3) for the ring-expansion carbonylation of epoxides to H" lactones.27-30 The resultant catalyst exhibits activity that is comparable to those of currently known active homogeneous catalysts and is significantly higher than those of reported heterogeneous catalysts for this reaction. In addition, this catalyst exhibits good recyclability and regeneration ability over consecutive runs. 2. RESULTS AND DISCUSSION 2.1 Synthesis and characterization of hypercrosslinked (TPP)AlCl (2) The synthetic scheme for the heterogenization of (TPP)AlCl (1) is shown in Scheme 2. Monomer 1 is hypercrosslinked by a modified synthetic procedure using dichloromethane as 4 ACS Paragon Plus Environment

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formed polymer 2 is the same as that of monomer 1, indicating that the core structure is maintained upon crosslinking (Figure S1-B), while the significant reduction in the intensity of the phenyl C-H stretching signal in the range of 3100-3020 cm: and the formation of a alkyl C-H stretching weak band around 2920–2960 cm: indicate that the phenyl groups are alkylated by methylene bridges.41-43 The chemical shifts observed by CP-MAS 13C NMR at 129, 138, and 146 ppm can be assigned to the carbon atoms of the phenyl rings and the porphyrin backbone of TPP, respectively (Figure S2).44 Furthermore, the broad resonance at 38 ppm confirms the presence of methylene carbon atoms formed through Friedel–Crafts crosslinking. This result is consistent with those previously reported for crosslinked metalloporphyrin polymers prepared by similar methods.45 The wide-angle powder X-ray diffraction pattern of 2 presents a broad peak centered at 2J = 21.9°, which reveals the formation of an amorphous carbonaceous polymeric material. The absence of characteristic crystalline peaks confirms that the crosslinking is completed and that the product is free from monomeric impurities (Figure S3). The pattern is comparable with those of similar porphyrin-based porous organic polymeric materials previously reported in the literature.40,46 The thermal stability of 2 was investigated by thermogravimetric analysis (Figure S4) to assess its durability under harsh temperature conditions and only 7% weight loss is observed at 100 °C, which might be due to the moisture absorptive nature of the material upon exposure to the atmosphere. When the temperature is raised to 350 °C, 90% of the polymer weight is retained. Thus, these results indicate that formation of the hypercrosslinked network around 1 confers thermal stability to the polymer.47 Additionally, the morphology of the polymer was investigated by scanning and transmission electron microscopies (SEM and TEM). As shown in Figure S5, the SEM images reveal a rough, non-uniform surface structure, and the TEM images further demonstrate the highly porous nature of the material. Energy dispersive X-ray spectroscopy (EDX) mapping indicates a uniform distribution of Al 6 ACS Paragon Plus Environment

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atoms and labile Cl- anions in an approximately equal ratio throughout the sample.34 The porosity of polymer 2 was studied in detail by sorption analysis using N2 as a sorbate. As shown in Figure 1a, the adsorption-desorption measurements performed at 77 K show typical type-I and type-IV isotherms according to the IUPAC classification of adsorption isotherms.48-49 The rapid uptake of N2 in the low-relative-pressure region (p/p0 = 0–0.1) may arise from the microporous nature of the polymer, while the hysteresis loop over the whole relative pressure range may be ascribed to the contributions of meso- and macroporosity. The uptake of N2 at a relative pressure above 0.9 might be attributed to meso-/macro structures and, in part, to interparticulate porosity. The Brunauer-Emmett-Teller specific surface area of 2 is 1,100 m2 g: , which is calculated from the data obtained in the relative pressure (p/p0) range 0.01–0.1. The total pore volume and average pore size are 1.1 cm3 g: and 3.8 nm, respectively (See Figure S6a). These surface area and pore volume results are comparable to those reported for porphyrin-based crosslinked polymers prepared using similar procedures and by different polymerization methods.33, 40-41, 46, 50-51 These porosity results demonstrate the high surface area and large pore volume of the catalyst, both of which are beneficial for effective mass transfer into the catalysts. Furthermore, they are also indicating the availability of large pore channels for the effective accommodation of Co(CO)4– anions to form a ([Lewis acid]+[Co(CO)4]–) catalytic structure.




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throughout the sample, even after washing several times with dry THF. The EDX spectra shows a very small amount of left out Cl, which might be get trapped inside the pores and not accessible for complete exchange (Figures 1c–d and S7).28-43 The FTIR spectrum reveals the presence of a new strong absorption peak at 1882 cm: , which is characteristic of Co(CO)4– anions, that is not presented by the non-exchanged sample, confirming the successful incorporation of Co(CO)4– anions into the polymeric framework of 2 as a frustrated Lewis acid-base pair through electrostatic interactions (Figure S1-C).27-29, 43, 52 This IR band value is consistent with those of well-defined Co(CO)4– anion exchanged homogeneous ([Lewis acid]+[Co(CO)4]–) type complexes used as carbonylation catalysts.20-24,

53

The Al and Co

loading in the framework was estimated by inductively coupled plasma-optical emission spectrometry (ICP-OES) and atomic absorption spectroscopy (AAS), revealing contents of 2.6 and 5.3 wt% for Al and Co, respectively. The Al/Co molar ratio is 1: 0.93 which is further corroborates to the maximum exchange of Cl– anions with Co(CO)4–. To characterize the coordination behavior of the metal species, X-ray photoelectron spectroscopy (XPS) studies were conducted. As shown in Figure 1e,f, the Al 2p3/2 XPS peak appears at 74.3 eV, which matches well with an Al(III) oxidation state and is close to that of salen-type Al(III) species in porous organic frameworks.27,

54

The XPS peaks at 781.6 eV and 797.2 eV along with

typical shoulders are characteristic of the Co 2p3/2 and Co 2p1/2 orbitals of the frustrated Co(CO)4–species, which matches well with similar Co(CO)4–-incorporated heterogeneous catalysts.27-28 Finally, retention of porosity is evident from the TEM images of 3, as shown in Figure 1b (see Supporting Information, Figure S8). The N2 sorption traces for 3 exhibit the same type-I and type-IV isotherm patterns and hysteresis loop behavior as those for 2, indicating the retention of the micro-, meso-, and macroporosity (Figure 1a and Figure S6-b) of the parent framework.48-49 However, the BET specific surface area is decreased to 760 m2 g: along with decreases in pore volume to 0.7 cm3 g: and average pore size to 3.7 nm. This 9 ACS Paragon Plus Environment


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indicates that Co(CO)4– anions partially occupy the pore channels of the framework, thereby reducing the total pore volume available. However, the framework still exhibits high porosity and maintains its average pore size, which can easily allow the substrate (epoxides) and product molecules to diffuse in and out of the framework.27-28 2.3 Catalytic Activity of 3 According to the mechanistic studies into ring-expansion carbonylation of epoxides with homogeneous catalysts reported by Coates et al., the solvent plays a significant role in carbonylation.23,

39

Therefore, the as-prepared heterogenized catalyst 3 was screened in

different solvents using propylene oxide (PO) as a substrate in a custom made 100-mL stainless steel tube reactor with 0.5 mol% catalyst loading at 60 °C under 60 bar of CO pressure for 24 h. 1H NMR spectroscopy analyses of the reaction mixtures showed that the conversion of -butyrolactone varies widely depending on the solvent medium, as shown in Figure S9. Of the solvents screened, 1,4-dioxane is the most effective, so this was adopted as the solvent of choice for all subsequent reactions (unless otherwise stated). Notably, similar solvent

effects

have

been

reported

in

[(ClTPP)Al(THF)2]+[Co(CO)4]–

(ClTPP

=

the

literature

for

the

well-defined

meso-tetra(4-chlorophenyl)porphyrinato)

homogeneous catalyst.39 The catalytic activity was evaluated in detail using the optimal solvent 1,4-dioxane under typical conditions of 0.1 mol% catalyst loading, 60 °C, and 60 bar of CO pressure for 24 h, and the results are shown in Table 1.


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Table 1. Catalytic activity of 3 in the ring-expansion carbonylation of epoxides O

+

O

Catalyst

CO

O

1,4-dioxane, 60 bar CO

R

R

O

+ R

Entry

Catalyst

-R

Solvent

T (°C)

PCO (bar)

Time (h)

[Epoxide]/ [Co] ratio

Yield (%)

Lactone/ Ketone

TONd

STY (h? )e

Ref

1

[(salph)Al(THF)2]+[Co(CO)4]-

n-Bu

neat

60

62

6

350

40

NA

140

23

21

2

[(salph)Cr(THF)2]+[Co(CO)4]-

Me

DME

22

1

6

50

98

96/04

47

8

24

3

[(OEP)Cr(THF)2]+[Co(CO)4]-

n-Bu

neat

60

62

6

4500

>99

NA

4500

750

22

4

[bpy-CTF-Al(OTf)2]+[Co(CO)4]-

Me

DME

50

60

24

30

>99

90/10

27

1

27

5

[(PPP)Cr(THF)2]+[Co(CO)4]-

Me

THF

60

60

20

1000

34

99/01

337

17

28

n-Bu

DME

60

60

1

200

88

NA

176

176

29

Me

Dioxane

60

60

24

1000

>99

>99

1000

-

This work

24

1000b

49c

>99

490

-

This work

65c

6 7a

Co(CO)4-

Cr-MIL-101

[(TPP)Al(THF)2

8a

3

]+[Co(CO)

4

]-

Me

Dioxane

60

60

9a

3

n-Bu

Dioxane

60

60

24

1000b

>99

650

-

This work

10a

3

n-Bu

Dioxane

60

60

24

500b

>99

>99

500

-

This work

11a

3

n-Bu

Dioxane

60

60

6

500b

86c

>99

430

-

This work

72c

>99

360

360

This work

10c

>99

53

53

This work

12a

3

n-Bu

Dioxane

60

60

1

500b

13a

3

n-Bu

Dioxane

30

60

1

500b

aReaction

performed in 1.8 M solution of epoxide in 4-dioxane solvent and pressurized using 60 bar of CO at room temperature and kept in a preheated oil bath to attain the desired temperature. bCalculated based on ICP-AAS value for Co content. cDetermined by 1H NMR spectroscopy using naphthalene as an internal standard (remaining is the unreacted epoxide). dTotal turnover number (TON) = mol e : -lactone/molCo. Site time yield (STY) = TON h throughout the overall reaction time. The homogeneous catalyst [(TPP)Al(THF)2]+[Co(CO)4]- is very effective and achieves >99% conversion and >99% selectivity toward -butyrolactone. Interestingly, the heterogeneous catalyst 3 is also active and converts 49% of the PO with >99% selectivity toward butyrolactone (entries 7 and 8, Figure S10) under the same conditions. The calculated TON of 490 for the heterogeneous catalyst is significantly higher than those for other reported heterogeneous catalysts and salph-based homogenous catalysts (compare entries 1, 2, 4–6, and 8).21, 24, 27-29 However, under similar conditions, if the PO substrate is changed to 1,2epoxyhexane, 65% conversion to the corresponding -lactone is achieved as the sole product 11 ACS Paragon Plus Environment


with a TON of 650 (entry 9, Figure S11). This TON is higher than that of any previously reported heterogeneous catalyst for the same reaction and is comparable with that of its homogeneous counterpart (entries 4–7).27-28 The origin of this reactivity trend, which correlates with the alkyl chain length of the –R group attached to the epoxide (vide infra), is attributed to polarity effects and, in part, the electronic properties of the alkyl chain attached to the epoxide, as reported by Coates et al.22 Furthermore, the boiling point of the epoxides increase in parallel with the alkyl chain length of the–R group, allowing more contact time for the epoxide with the catalyst at higher temperatures. Thus, we used the epoxide with the longer alkyl group (1,2-epoxyhexane) to assess the real activity of the catalyst. To avoid the presence of unreacted epoxides in the reaction mixture and to allow facile separation of the product from the catalyst, reactions were performed using a lower substrate-to-catalyst ratio (entry 10, Figure S11). When using an epoxide ratio of 500, complete conversion is achieved with the H"

as the only product. Impressed by higher activity of the catalyst under

these conditions, reactions were performed to obtain the initial conversion rates for 6 h and 1 h under similar reaction conditions in 1,4-dioxane (entries 11 and 12). The carbonylated yields were 86 and 72%, respectively, with an STY of 360 h: for 1 h. Though initial STY is lower than that of the highly active homogeneous catalyst (entry 3),22 it is far higher than those of other homogeneous catalysts for this carbonylation reaction (entries 1 and 2),21, 24 and this is the highest STY value reported for any heterogeneous catalyst for this reaction to date (entries 4–6).27-29 Even though, all the ([Lewis acid]+[Co(CO)4]–)-type catalysts are proposed to have the same rate determining step, Coates et al reported that the origin of much greater epoxide carbonylation activity of [(TPP)Al(THF)2]+[Co(CO)4]: system is that the increased delocalization of charge into the porphyrin ligands, which stabilizes the ratedetermining transition state as the Al center is converted from a formally neutral alkoxide to a cationic species.39 Similar reason holds good for the excellent activity of this heterogenized 12 ACS Paragon Plus Environment

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2.4 Substrate Scope The versatility of the catalyst was evaluated through the carbonylation of a variety of functionalized epoxides (Table S2, supporting information). Importantly, 3 exhibits a broad range of functional group tolerance toward ring-expansion carbonylation performed under similar conditions. The activity varies with the length of the pendant alkyl group in an array of aliphatic epoxides (entries 1–4). PO has a total TON of 490, but this increases to 520 for 1,2-epoxybutane and further increases to 650 and 700 for 1,2-epoxyhexane and 1,2epoxydodecane, respectively. This activity trend and its relationship to alkyl chain length has been explained already (vide supra). Glycidyl ethers can be carbonylated successfully to yield hydroxymethyl lactone derivatives, while ethers with unsaturated allyl groups and ester groups show only moderate activities (entries 5–7). Aryl groups are also tolerated to afford the corresponding lactone (entry 8). Substrates with more than one epoxide can also undergo multiple ring-expansion carbonylations (entry 9). It is also noteworthy that the heterogenized catalyst tolerates epoxides with various lengths and types of functional groups to afford the corresponding functionalized -lactone derivatives, demonstrating the potential applicability this heterogeneous catalyst to a variety of substituted epoxide carbonylations.22 2.5 Recyclability Before the recyclability studies, the heterogeneous nature of the catalyst was confirmed by a hot filtration test in which a 1,4-dioxane suspension of 3 was subjected to the reaction temperature of 60 °C for 6 h and then isolated by simple filtration.27-28 When the acquired filtrate and the filtered solid catalyst were both subjected separately to the standard reaction conditions for the carbonylation of PO, the solid catalyst effects full conversion of PO to the lactone, whereas the filtrate does not show any lactone conversion (See Figure S13, 14 ACS Paragon Plus Environment

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Supporting Information). The cooperative effects of the Lewis-acidic Al(III) sites and the Lewis-basic Co(CO)4– in 3 was verified by assessing the individual catalytic activities of 2 and KCo(CO)4 for PO carbonylation. Both systems show negligible activity toward lactone conversion when subjected to 6 h reaction time with 1.0 mol% of catalyst at 60 bar CO pressure. However, when equimolar amounts of Lewis-acidic 2 and KCo(CO)4 were used for epoxide carbonylation under the same reaction conditions, full conversion of the epoxide is achieved, presumably due to the in situ formation of Lewis-acidic Al(III) and Lewis-basic Co(CO)4- pairs in the reaction medium.14 The observed activity is comparable with that of heterogeneous 3 (See Table S3 and Figure S14, Supporting Information), which contains electrostatically paired well defined Al(III)/Co(CO)4– cooperative sites preassembled within the hypercrosslinked structure.29 Finally, the recyclability of 3 for the carbonylation of 1,2epoxyhexane was assessed following reactions performed at 30 °C for 6 h in 1,4-dioxane under 60 bar CO pressure. After the initial run, the reaction mixture was simply filtered inside the glove box, washed, dried under vacuum, and used for successive cycles. After complete conversion in the initial two cycles, the recovered catalyst was used further in the next cycle.27-28, 43,52, 55 As shown in Table 2 (See Figure S15 in supporting information for 1H NMR spectra) the activity decreases from complete conversion to 85±6% in the third cycle and further to 22±5% in the fourth cycle. To investigate the reason for this reduced activity upon recycling, the catalyst recovered after the first cycle was subjected to IR spectral analysis and compared with a fresh catalyst to observe any changes in the structure of the catalyst. Interestingly, the structural integrity of the catalyst is retained along with the carbonyl peak at 1882 cm: , which is characteristic for [Co(CO)4–] (See Supporting Information, Figure S16).27-28 However, analysis of the recovered catalyst after the third cycle shows only minimal presence of the characteristic carbonyl peak at 1882 cm: and this 15 ACS Paragon Plus Environment


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peak is not observed after the fourth cycle (See Figure S16). Thus, it was concluded that the decreased activity of the catalyst after the third cycle might be due to decreasing Co content in the catalyst as a result of leaching, as has been reported for similar systems.27-28,

43, 52

Furthermore, XPS analysis of the recovered catalyst after two cycles was performed, revealing no significant changes in the binding energies of the Al and Co species compared to those of the fresh catalyst (See Figure S17, Supporting Information), which indicates that there is no change in the coordination environment of the Lewis-acidic Al(III) or the Lewisbasic cobaltate centers. SEM-EDX analysis of the catalysts recovered after each cycle shows no morphological changes in the catalysts, but there is a decrease in the Co/Al ratio after every cycle (Figures S18–S21). After the first cycle, the Co/Al ratio is 80%, which is further reduced to 49% and 46% after the third and fourth cycles, respectively. This is further confirmed by ICP-AAS analysis of the filtrate, which revealed that leaching of the Co content after each cycle. Therefore, acquired catalytic yields decreased after third cycle, to recover the catalytic activity, the spent catalyst was regenerated by treatment with K[Co(CO)4] and the activity was assessed again.24-25, 43, 52

To our delight, the activity is restored, affording a

catalyst that promotes complete conversion of the epoxide with >99% selectivity toward the H"

5 This unambiguously proves that Co leaching is the cause of the loss of activity

upon recycling, and that this can be rectified by a simple regeneration method. However, drastic decrease in the activity after third cycle without much further decrement in Co content looks wary of such an unambiguity and suggests that there may be factors other than Co leaching that led to catalyst deactivation during recyclability. The origin of the Co leaching and the mechanism of catalyst deactivation are currently under investigation.


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Table 2. Recyclability of 3. Selectivity (%) Cycle

Yield (%) H"A

N,

1

> 99

> 99/ < 1

2

> 99

> 99/ < 1

3

85±6

> 99/ < 1

4

22±5

> 99/ < 1

5a

> 99

> 99/ < 1

Reaction condition: 2 mol% of catalyst, 60 bar of CO, 30 °C, for 6 h, solvent 1,4-dioxane. Conversion was calculated by 1H NMR measurements with naphthalene as an internal standard. aRegenerated catalyst.

3. CONCLUSIONS In conclusion, we have demonstrated a design strategy for the direct heterogenization of a highly active homogeneous catalyst for the ring-expansion carbonylation of epoxides using a simple Friedel–Crafts reaction. The heterogeneous catalyst prepared is highly porous and very effective for the carbonylation of a variety of epoxides. Its activity is comparable to those of active homogeneous catalysts having a maximum TON of 650 and an STY of 360 h 1,

which are the highest values reported for any heterogeneous catalyst for this reaction to

date. The ease of preparation, excellent catalytic performance, facile separation, and excellent recycling ability make it a viable candidate for industrial applications.

4. EXPERIMENTAL SECTION Detailed synthetic procedures and characterization results are available in Supporting Information ASSOCIATED CONTENT 17 ACS Paragon Plus Environment


Supporting Information The Supporting Information is available free of charge on the ACS Publications website General considerations and Characterization techniques, detailed synthetic procedures, Experimental procedures, Characterization results, figures and tables are available in supporting information. AUTHOR INFORMATION Corresponding Author *[email protected] Funding Sources The authors declare no competing financial interest. Notes Toxic carbon monoxide containing chemicals dicobaltoctacarbonyl, potassium tetracarbonyl, newly synthesized catalyst 3 and high pressured carbon monoxide gas was used in this work. ACKNOWLEDGEMENT This work was supported by C1 Gas Refinery Program (2018M3D3A1A01018006) through the National Research Foundation of Korea (NRF) funded by Ministry of Science, ICT and Future Planning, Republic of Korea. Conflict of Interest The authors declare no conflict of interest REFERENCES 1.

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A Hypercrosslin,ed Porous Porphyrin Aluminum(III) - ACS Publications

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