1 Introduction
Biomass has been considered to be the most attractive sustainable sources for fuels and bulk chemical feedstocks [1–5]. 5-Hydroxymethyl-2-furfural (HMF), one of the major biomass platform chemicals, can be obtained from acid-catalyzed dehydration of cellulose and its derived C6 carbohydrates can be converted into a variety of biofuels, fine chemicals and pharmaceuticals [6–8]. Recently, the oxidation of HMF has attracted increasing attention since its final product, 2,5-furandicarboxylic acid (FDCA), has been listed as one of the top 12 building-block chemicals by the US Department of Energy and is regarded as a promising alternative to petroleum-derived terephthalic acid for the manufacture of key polyesters and polyamides [9–12]. A wide variety of metal catalysts, especially noble metal nanocatalysts, such as Au [13,14], Pt [15–17], Pd [18–20], Ru [21] and Au-Pd alloy [22,23], supported on different carriers, including metal oxides [13,16–18], carbon materials [21,22], zeolite [14], hydroxyapatite [20] and zinc hydroxycarbonate [23], have been developed for the catalytic aerobic oxidation of HMF toward FDCA in water with satisfactory catalytic efficiency by using molecular oxygen or air as the green oxidant. In most cases, however, a large excess of homogeneous base, such as NaOH or Na2CO3, was required, greatly limiting their practical applications due to the potential equipment corrosion and environmental pollution, as well as the need of neutralization reaction to isolate the acid products.
Consequently, it is highly desirable to develop new catalyst systems for the aerobic oxidation of HMF without the use of homogeneous base. Some progress has been achieved. Hydrotalcite- or basic oxide-supported Au [24–26], Pd [27] and Au-Pd alloy [28,29] nanocatalysts were reported to be active for the aerobic oxidation of HMF toward FDCA in water in the absence of a liquid base. However, the instability of these solid base supports under the reaction conditions was always an issue, and partial dissolution of the support often occurred. Different carbonaceous materials such as functionalized carbon nanotube [30,31], activated carbon [32], and N-doped carbon materials [33–35] were applied to support Au-Pd alloy, Pt or Ru catalysts for the base-free oxidation of HMF to FDCA in the aqueous phase, but the corresponding Ru catalysts exhibited relatively low catalytic activities with the yields of FDCA no more than 90%. Whereas Mn-Ce [36] or Mn-Co [37] mixed oxide-supported Ru nanocatalysts demonstrated high catalytic performance (>99% FDCA yields), due mainly to the strong metal-support interaction and unique support composition. Pt supported on other solid base materials, such as C–O–Mg [38] and N-doped carbon decorated CeO2 [39], were reported to be efficient and stable catalysts for the aqueous-phase aerobic oxidation of HMF to FDCA without a homogeneous base, in which the surface structures and properties of the supports were crucial.
It can be noticed that some attention has been paid to the inorganic solid material-supported nanocatalysts for the liquid-base-free aerobic oxidation of HMF to FDCA, however, the reports about the organic polymer-based catalysts to date have been very limited. Siankevich et al. [40] reported the Pt nanocatalysts stabilized by an ionic polymer (IP) or polyvinyl pyrrolidone (PVP) for the oxidation of HMF in water without the addition of any liquid base. IP was a porous solid that was insoluble in water, and the corresponding catalyst Pt/IP was active and stable for the oxidation reaction. While Pt/PVP that was well-dispersed in water afforded relatively low catalytic activity and suffered difficulties in separation and recovery. A cation-exchange resin-supported Pt catalyst, with a high Pt loading of 15.6 wt-%, was applied for the continuous-flow oxidation of HMF to FDCA in water, affording high catalytic performance and long-term resistance [41].
Recently, water-soluble thermosensitive polymers, with a smart feature of reversible solubility changes upon temperature variation, have attracted extensive attention because of their great potential in targeted drug delivery [42,43], enzyme immobilization [44–46], and chemical catalysis [47–50]. By changing the system temperature, it is highly desirable to realize a reaction process of “quasi-homogeneous catalysis, heterogeneous recycle” using such smart polymer supported nanocatalysts. Consequently, herein we explored a novel thermoresponsive block copolymer containing imidazole groups, with an upper critical solution temperature (UCST) of about 45 °C, for use as a support to stabilize Pt nanoparticles. The produced Pt nanocatalysts were evaluated in the base-free oxidation of HMF toward FDCA by molecular oxygen in water. They were well water-dispersed and exhibited high catalytic activity above the UCST. And they could be easily recovered for reuse by decreasing the system temperature to below the UCST. This preliminary study may shed light on the development of base-free HMF catalytic oxidation systems as well as that of new thermoresponsive nanocatalysts.
2 Experimental
2.1 Materials
Acrylamide (99%) was obtained from Energy Chemical and recrystallized from acetone before use. Acrylonitrile (99%) was provided by Aladdin Chemicals Co., Ltd. and purified by 8 wt-% NaOH aqueous solution. 2,2-Azobisisobutyronitrile (AIBN, AR) was purchased from Wako Pure Chemical Ind., Ltd. and recrystallized from ethanol. N-Vinylimidazole (99%) was supplied by Macklin Biochemical Co., Ltd. in Shanghai. Hexachloroplatinic acid hexahydrate (H2PtCl6·6H2O, AR) was obtained from Aldrich. HMF (97%) and FDCA (98%) were supplied by Heowns Biochemical Technology Co., Ltd. 5-Hydroxymethyl-2-furancarboxylic acid (HMFCA, 98%) was obtained from Matrix Scientific. 5-Formyl-2-furancarboxylic acid (FFCA, 98%) was purchased from Toronto Research Chemicals Inc. 2,5-Diformylfuran (DFF, 98%) was provided by Sun Chemical Technology Co., Ltd.
2.2 Characterization
The fourier transform infrared spectroscopy (FTIR) spectra were collected on a Bruker Tensor 27 spectrometer. The 1H nuclear magnetic resonance (NMR) spectrum was obtained with a Varian Mercury Vx-300 (300 MHz) spectrometer. The turbidity measurements were performed at 500 nm using an ultraviolet-visible (UV-Vis) spectrophotometer (Shimadzu UV-2550) equipped with a Shimadzu TCC-240A temperature controller and deionized water was used as a reference for 100% transmittance. The transmission electron microscopy (TEM) images of the specimens were obtained on an FEI Tecnai G2 F20 electron microscope with an accelerating voltage of 200 kV. The X-ray photoelectron spectroscopy (XPS) characterization of the Pt catalyst was performed on a Kratos Axis Ultra DLD spectrometer with a monochromatic Al Kα X-ray source (hν = 1486.6 eV). The scanning electron microscopy (SEM) images of the specimens were obtained on a JEOL JSM-7500F field-emission scanning electron microscope. The contents of Pt in the catalysts as well as in the reaction solutions were determined by inductively coupled plasma-atomic emission spectrometry (ICP-AES) on an ICP-9000(N+ M) spectrometer (TJA Co.). The pH values were measured by means of a Rex PHS-3C pH meter with an E-201-C pH electrode. Conversions and product yields were determined by high-performance liquid chromatography (HPLC) using an Agilent 1200 series liquid chromatograph equipped with a UV-Vis detector operating at 271 nm. A Sepax Carbomix H-NP10:8% column was used with a column temperature of 65 °C and a H3PO4 aqueous solution (1 mmol·L–1) was applied as the mobile phase at a flow rate of 0.6 mL·min–1.
2.3 Catalyst preparation
2.3.1 Synthesis of the block copolymer
The block copolymer was synthesized through a reversible addition-fragmentation chain transfer (RAFT) polymerization by using cumyl dithiobenzoate (CDB) as the RAFT agent and AIBN as the initiator (Scheme 1). CDB was synthesized as described previously [41].
First, dithiobenzoate-terminated poly(acrylamide-co-acrylonitrile), denoted as P1, was synthesized as follows. In a 25-mL Schlenk flask, acrylamide (5 mmol) and acrylonitrile (3 mmol) were dissolved in dimethylsulfoxide (DMSO, 5 mL). Then AIBN (0.08 mmol) and CDB (0.04 mmol) were added, and the resulting reaction mixture was stirred for 0.5 h under N2 atmosphere at room temperature, followed by being heated to 80 °C for 48 h. Thereafter, the mixture was cooled to room temperature. The produced polymer was precipitated in methanol, separated by filtration, and washed with methanol. After drying at 60 °C under vacuum, the yellowish solid P1 was obtained. FTIR: 3430, 3345, 3197 (νN–H); 2930 (νC–H); 2242 (νC≡N); 1667 (νC= O) cm–1.
Then, to a solution of P1 (250 mg) in DMSO (5 mL) was added N-vinylimidazole (4 mmol) and AIBN (0.04 mmol). The reaction mixture was stirred for 0.5 h under N2 atmosphere at room temperature and then heated to 80 °C for 48 h, followed by being cooled to room temperature. The block copolymer, poly(acrylamide-co-acrylonitrile)-b-poly(N-vinylimidazole), denoted as P2, was then obtained as a yellowish powder by precipitation with acetone, filtration, washing with acetone, and drying at 60 °C under vacuum. FTIR: ~3400, 3197 (νN–H); 3105 (ν=C–H); 2930 (νC–H); 2242 (νC≡N); 1667 (νC=O); 1497 (νC=C) cm–1. 1H NMR (300 MHz, DMSO): δ (ppm) 1.4–2.2 (–CH2–), 2.6–3.3 (–CH–), 6.5–7.5 ( =C–H).
2.3.2 Synthesis of P2-stabilized Pt nanocatalysts
In a typical synthesis, an ethylene glycol solution of H2PtCl6·6H2O (38 mmol·L–1, 4.0 mL) and an aqueous solution of NaOH (2.5 mol·L–1, 1.0 mL) were added in ethylene glycol (5 mL) with vigorous stirring for 0.5 h under N2 atmosphere. The resulted orange-yellow solution was then heated to 160 °C and kept for 3 h, followed by being cooled to room temperature. The Pt nanoparticles were precipitated by adjusting the pH of the solution lower than 4.0 with a diluted HCl solution (1.0 mol·L–1) and collected by centrifugation. After washing with deionized water thrice, the Pt nanoparticles were re-dispersed in deionized water (10 mL). Afterward, to an aqueous solution of a certain amount of P2 (9 mL) was added the above-mentioned Pt dispersion (1 mL). The reaction mixture was stirred at 60 °C for 2 h. The product was precipitated by cooling the reaction mixture to room temperature, separated by centrifugation, washed thrice with deionized water, and then re-dispersed in deionized water (10 mL). The resulting specimen was denoted as Pt/P2-x (x = 20, 40, 60, 80) solution, where x represents the amount of P2 used in the synthesis procedure (mg). The ICP-AES analysis determined that the Pt concentration in the sample was 1.5 mmol·L–1. And the control experiment showed that there was no detectable Pt species in the aqueous solution after isolating Pt/P2-x from the sample.
For comparison, Pt/P1 was also synthesized according to the above-mentioned procedure by the replacement of P2 by P1 (40 mg).
2.4 HMF oxidation
A typical procedure for HMF oxidation reaction was as follows. A solution of HMF (0.075 mmol) in deionized water (3 mL) and the above-synthesized Pt/P2-x solution (2 mL) were charged into a 30-mL stainless steel autoclave equipped with a magnetic stirring bar. After being purged with pure O2 for five times, the autoclave was pressurized to the desired pressure with O2 (2–8 bar) and immersed into a pre-heated oil bath with the reaction mixture being stirred. After the reaction was over, the catalyst was precipitated by cooling the reaction mixture to room temperature, separated by centrifugation, and washed with deionized water. The liquid phase was subjected to HPLC analysis. For the recycling experiment, the recovered Pt nanocatalyst was re-dissolved in deionized water and subjected to a new run with fresh reactants under the same reaction conditions.
3 Results and discussion
3.1 Catalyst characterization
The as-synthesized Pt/P2-x catalysts were characterized by TEM. Figure 1 shows the typical TEM image of Pt/P2-40. Uniformly dispersed Pt nanoparticles were observed. The histogram of particle size distribution, based on the measurement of more than 150 Pt nanoparticles, indicated a very narrow size distribution of Pt nanoparticles in the range of 1.3–2.4 nm with an average particle size of ca. 1.9 nm. Similar TEM results were obtained for other catalysts.
The Pt 4f XPS spectrum of Pt/P2-40 is depicted in Fig. 2. Two peaks ascribed to Pt 4f7/2 and Pt 4f5/2 were observed, which could be deconvoluted into four sub-bands. The components located at about 70.7 and 74.1 eV could be assigned to Pt 4f7/2 and Pt 4f5/2 of Pt0, respectively. And the minor components appeared at about 71.8 and 75.4 eV could be attributed to Pt2+ species. The results of XPS characterization indicated that Pt predominantly existed as Pt0 species in the catalyst, along with about 30% of oxidized Pt2+ species.
The thermoresponsive properties of the catalysts Pt/P2-x were investigated by the measurement of the turbidity in 0.5 wt-% aqueous solutions with the observation of the 00 nm UV transmittance. Figure 3 shows the representative turbidity curves for the 0.5 wt-% aqueous solutions of P2 and Pt/P2-40. Both the two specimens showed a UCST of about 45 °C and a rapid decrease in the transmittance of the solutions was observed as lowering the temperature from 50 °C to 40 °C. For the purpose of comparison, the thermoresponsive property of polymer P1 was also tested. As shown in Fig. S1 (cf. Electronic Supplementary Material, ESM), P1 exhibited an almost identical turbidity curve to P2, suggesting that the thermosensitivity was mainly contributed by the segment of poly(acrylamide-co-acrylonitrile). The observed phase transition behavior was associated with the enhanced inter-/intra-chain hydrogen bonding interaction between the carbonyl and amino groups upon cooling [51], which forced the polymer to appear in a collapsed globule structure and precipitated from water. As a consequence, Pt/P2-40 was well-dispersed in deionized water at 55 °C but precipitated at 35 °C. This thermoresponsive character is highly desirable for HMF oxidation reaction that is often performed at a temperature higher than this UCST.
3.2 Reaction pathways for base-free oxidation of HMF to FDCA over Pt/P2-x
The as-synthesized catalysts Pt/P2-x were evaluated in the aqueous-phase aerobic oxidation of HMF to FDCA without the assistance of any base additive. For the purpose of comparison, polymer P2 was also investigated under the identical reaction conditions. No HMF conversion was detected (Table 1, entry 1), indicating that the polymer was catalytically inactive in this reaction system.
Tab.1 Catalytic performance of different catalyst systems for the aerobic oxidation of HMF a) |
| Entry | Catalyst | PI/μmol b) | HMF conv./% | Yield/% | |||
|---|---|---|---|---|---|---|---|
| HMFCA | DFF | FFCA | FDCA | ||||
| 1 | P2 | 0 | 0 | 0 | 0 | 0 | 0 |
| 2 | Pt/P2-40 | 0 | 100 | 0 | 0 | 0 | >99.9 |
| 3 | Pt/P1 | 0 | 79.4 | 0 | 12.5 | 20.2 | 46.7 |
| 4 | Pt/P1 | 5 | 63.4 | 4.5 | 2.8 | 40.3 | 15.8 |
| 5 | Pt/P1 | 50 | 55.9 | 3.3 | 5.0 | 34.6 | 13.1 |
| 6 | Pt/P1 | 300 | 40.6 | 2.0 | 2.9 | 25.4 | 10.2 |
| 7 | Pt/P2-20 | 0 | 100 | 0 | 0 | 11.8 | 88.2 |
| 8 | Pt/P2-60 | 0 | 100 | 0 | 0 | 10.9 | 89.1 |
| 9 | Pt/P2-80 | 0 | 100 | 0 | 4.6 | 41.6 | 53.8 |
Figure 4 shows the reaction profiles for HMF oxidation over Pt/P2-40 at 100 °C under O2 pressure of 8 bar. FFCA and DFF were the major intermediate products for this reaction system, along with a very little amount of HMFCA (<1%) detected within the first 1 h. The yield of DFF reached 15% in 1 h and began to decrease to zero after 6 h of reaction. And the yield of FFCA reached 54% within 2 h and then underwent a continuous decline. A complete conversion of HMF was achieved in 6 h, and the yield of FDCA monotonically increased with prolonging the reaction time, reaching>99.9% after 12 h. All these observations suggested that the formation of DFF intermediate via oxidation of the hydroxymethyl group in HMF was he ominant athway for HMF xidation ver Pt/P2-x catalysts (Scheme 2).
It was reported that the soluble base had a dramatic impact on the aldehyde oxidation by the formation of a geminal diol intermediate and its consequent dehydrogenation conversion toward a carboxylic acid function, thus HMFCA was always generated as one of the major intermediate products in the presence of a liquid base [13–23,52]. While the present reaction solution showed a rather moderate pH of 7.5 in the initial period, which sharply decreased to about 3.0 after 2 h of reaction due to the production of the acidic products, including FFCA and FDCA. On the other hand, Pt nanocatalysts had been reported to be highly effective for the aerobic oxidation of the alcohol function in HMF by promoting the activation of the C–H bond in the hydroxymethyl group and facilitating the elimination of β-H atom to form an aldehyde group [17,31,40]. Therefore, DFF was formed initially as a reaction intermediate for Pt/P2-x catalyzed base-free aerobic oxidation of HMF.
Based on the reaction results, it could be concluded that HMF was rapidly oxidized by Pt/P2-x to produce DFF, followed by a continuous oxidation to generate FFCA and further FDCA. The relatively low yield of DFF throughout the reaction indicated that the oxidation process of DFF to FFCA was fast. Whereas on the contrary, FFCA was the main product during the initial reaction stage with a higher yield than DFF and FDCA, suggesting that the conversion of FFCA to FDCA was the slowest step in the entire oxidation process from HMF to FDCA.
3.3 The role of imidazole functional group in P2 on aerobic oxidation of HMF
To investigate the role of the imidazole functional groups in polymer P2, a control experiment with Pt/P1 as the catalyst was performed. As shown in Table 1, Pt/P1 exhibited notably inferior catalytic performance compared with Pt/P2-40, giving a low FDCA yield of 46.7% with an HMF conversion of 79.4% after 12 h (Table 1, entry 3). This indicated that the presence of imidazole groups in the polymer could significantly enhance the catalytic behavior of the catalyst.
For a further comparison, a certain amount of PI, a weak organic base with a similar structure to the imidazole groups in polymer P2, was added into the reaction system catalyzed by Pt/P1. Interestingly, it was found that the addition of PI did not facilitate the catalytic reaction; conversely, it had a distinct inhibiting effect on the catalytic activity of Pt nanocatalyst. The presence of even a small amount (5 μmol) of PI caused a significant decrease in FDCA yield (Table 1, entry 4). In addition, this inhibiting effect became stronger with the increase in the amount of PI. When 50 μmol of PI, which was approximately equivalent to the amount of imidazole groups in the catalyst of Pt/P2-40, was added, the yield of FDCA decreased further to 13.1% (Table 1, entry 5). Furthermore, a certain amount of HMFCA arose in the products when PI was used. This inhibiting effect may be derived from the competitive adsorption of PI molecules and reactants on the surface of Pt nanoparticles, which led to lower probability of contact between reactants and catalytic active sites, thus resulting in inferior catalytic efficiency.
Based on these comparison results, we could then conclude that combining the imidazole groups into the polymer structure produced a promising carrier of Pt for the liquid-base-free oxidation of HMF. The promotion of catalytic activity by the imidazole groups in polymer P2 was probably associated with the π–π interaction between the imidazole ring and furan ring, leading to the enrichment of reactants surrounding the polymer molecules.
It is noteworthy that the RAFT polymerization with CDB represents a living radical polymerization process, which allows the facile synthesis of block copolymers and makes it possible to design target polymers at the molecular level. The segment of poly(acrylamide-co-acrylonitrile) derived from the copolymerization of acrylamide and acrylonitrile was responsible for the distinct thermosensitivity of polymer P2, where the UCST could be regulated by tuning the molar ratio of acrylamide to acrylonitrile. Whereas the segment of poly(N-vinylimidazole) was beneficial for promotion of the catalytic activity of Pt/P2-x. By using this strategy, it is highly promising to design diverse thermoresponsive polymers as catalysts or catalyst supports for varying catalytic processes.
3.4 Effect of the ratio of P2 to Pt on catalytic performance
To study the influence of the ratio of P2 to Pt in the catalyst on the catalytic performance, the supported catalysts Pt/P2-x with different amounts of polymer P2 were evaluated in the oxidation of HMF. Pt/P2-40 exhibited the best catalytic performance, giving a high FDCA yield of>99.9% after 12 h (Table 1, entry 2). With further increasing the ratio of polymer to Pt, a gradual decline in catalytic activity was observed (Table 1, entries 8 and 9). For example, the yield of FDCA decreased to 53.8% over Pt/P2-80 under the same reaction conditions, along with 4.6% unconverted DFF. The decrease in catalytic performance may be related to the enhanced steric hindrance for reactant access to the surface of Pt nanoparticles that were surrounded by more polymer segments. When the catalyst of Pt/P2-20, with a relatively low ratio of P2 to Pt, was used, lower reaction activity compared with Pt/P2-40 was also presented (Table 1, entry 7). The TEM characterization showed that Pt nanoparticles were well dispersed without agglomeration with an average particle size of ca. 2.0 nm for the catalyst Pt/P2-20 after being used in the oxidation reaction of HMF (Fig. S2, cf. ESM), suggesting that this amount of polymer was able to effectively stabilize Pt nanoparticles. Thus the inferior catalytic activity of Pt/P2-20 may be associated with the relatively low content of imidazole groups in Pt/P2-20.
3.5 Effects of O2 pressure and reaction temperature on catalytic performance
The effects of O2 pressure and reaction temperature on the catalytic performance were investigated by using Pt/P2-40 as a model catalyst. HMF achieved a complete conversion in 12 h for all the cases studied. However, as shown in Fig. 5, obvious dependences of the FDCA yield on the O2 pressure and reaction temperature were observed. When the O2 pressure was raised from 2 to 8 bar, an increase in the yield of FDCA from 80.1% to>99.9% was achieved (Fig. 5(a)). Oxygen was believed to serve as a sacrificial electron acceptor and consume excess electrons on the Pt surface generated from the three-step oxidant reaction from HMF to FDCA [52,53]. The present results indicated that within the studied O2 pressure range, more O2 in the reaction system could facilitate the reaction. By increasing the reaction temperature from 70 °C to 100 °C, the yield of FDCA increased from 63.4% to>99.9% (Fig. 5(b)). It should be noted that the catalytic performance achieved over the present catalyst Pt/P2-40 is at the high level as compared with those of diverse noble metal nanocatalysts previously reported for the base-free oxidation of HMF in neat water under O2 atmosphere (Table S1, cf. ESM).
3.6 Catalyst recycling and stability
The stability and reusability of Pt/P2-x catalysts in the aerobic xidation of HMF were investigated using Pt/P2-40 as a model catalyst (Fig. 6). As described above, the catalyst Pt/P2-40 possessed a thermoresponsive phase transition behavior in aqueous solution with a UCST of about 45 °C. That is, it was well dispersed during the oxidation reaction carried out at 100 °C (Fig. 6(a)). After the oxidation reaction, it could be precipitated from the reaction mixture by cooling the reaction system to room temperature and recovered for reuse (Fig. 6(b)).
As shown in Fig. 6(c), the catalyst still remained high catalytic performance after five cycles with an FDCA yield of 95.7%, though a gradual and slight decrease in the yield of FDCA occurred during the durability test. The ICP-AES analysis showed that the Pt content in the supernatant after each cycle was less than 1.2 mg·L−1, corresponding to a Pt leaching of no more than 1%. This indicated that the catalyst Pt/P2-40 could be well recovered from the reaction mixture based on its thermosensitivity. Characterization of the used catalyst by TEM disclosed that Pt nanoparticles were still homogeneously dispersed with no obvious agglomeration and their average particle size remained relatively constant at about 2.0 nm (Fig. 7), suggesting the high stability of the present Pt catalyst in the aerobic oxidation system. The results of SEM and FTIR analyses, as shown in Figs. S3 and S4 (cf. ESM) respectively, also demonstrated that the catalyst showed no obvious change after undergoing the oxidation reaction.
4 Conclusions
The imidazole-containing thermoresponsive block copolymer P2 with a UCST of about 45 °C was synthesized through RAFT polymerization and applied to stabilize Pt nanoparticles, affording a kind of effective Pt nanocatalysts for the liquid-base-free aerobic oxidation of HMF toward FDCA in water. The supported Pt nanocatalysts Pt/P2-x, with a similar UCST to the block copolymer, were well-dispersed and formed a quasi-homogeneous catalytic system for the oxidation reaction, providing high catalytic performance. Especially, the catalyst Pt/P2-40 exhibited the best catalytic activity with FDCA yields up to>99.9%. The oxidation reaction proceeded via DFF and FFCA formation to produce FDCA and the promotion of catalytic activity by the imidazole functional groups in P2 was determined. Moreover, a heterogeneous separation and recovery of catalyst could be easily realized after the reaction by cooling down the reaction mixture below the UCST. The Pt catalysts showed good stability and reusability, and could be reused for five times with a slight loss in catalytic activity. These results suggested a great potential for industrial application of these thermoresponsive block copolymer supported nanocatalysts. More importantly, it is facile to alter the property of the block copolymer, by adjusting the composition of polymer chain segments, to widen its applications in other catalytic systems.