Anaerobic Alcohol Conversion to Carbonyl Compounds over

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Cite This: J. Phys. Chem. Lett. 2019, 10, 2075−2080

Anaerobic Alcohol Conversion to Carbonyl Compounds over Nanoscaled Rh-Doped SrTiO3 under Visible Light Guixia Zhao,*,† G. Wilma Busser,† Christian Froese,†,‡ Bin Hu,†,‡ Shannon A. Bonke,‡ Alexander Schnegg,‡ Yuejie Ai,§ Dongli Wei,§ Xiangke Wang,§ Baoxiang Peng,†,‡ and Martin Muhler*,†,‡

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†

Laboratory of Industrial Chemistry, Faculty of Chemistry and Biochemistry, Ruhr-Universität Bochum, Universitätsstrasse 150, 44780 Bochum, Germany ‡ Max Planck Institute for Chemical Energy Conversion, D-45470 Mülheim an der Ruhr, Germany § College of Environmental Science and Engineering, North China Electric Power University, Beijing 102206, P. R. China S Supporting Information *

ABSTRACT: Photocatalytic oxidation of organic compounds on semiconductors provides a mild approach for organic synthesis and solar energy utilization. Herein, we identify the key points for the photocatalytic oxidation over Pt-loaded Rh-doped strontium titanate allowing the conversion of alcohols efficiently and selectively to aldehydes and ketones under anaerobic conditions and visible light with an apparent quantum efficiency of pure benzyl alcohol oxidation at 420 nm of ≤49.5%. Mechanistic investigations suggest that thermodynamically the controlled valence band edge position via Rh doping provides a suitable oxidation ability of photogenerated holes, avoiding the powerful hydroxyl radical intermediates prone to overoxidation resulting in high selectivity. Kinetically, oxygen vacancies induced by Rh3+ substitution in the SrTiO3 lattice not only favor the dissociative adsorption of alcohols yielding alkoxy species but also induce the weakening of the α-C−H bond facilitating its cleavage by the photogenerated holes. Pt nanoparticles deposited as a cocatalyst contribute to the final hydrogen evolution.

C

oxyhalides, and sulfides is severly limited by the less positive valence band position, which is suitable for obtaining high selectivity as reported recently.20−23,26−30 However, as typically stable semiconductors, oxide photocatalysts have not yet been investigated for alcohol dehydrogenation under visible light, and the activation of the α-C−H bond by the photocatalyst under anaerobic conditions and the identification of the reaction site have not been fully investigated. Here, by using Rh-doped strontium titanate (Rh-STO) loaded with Pt nanoparticles (NPs) as a prototypical model system, we achieved stable and selective alcohol dehydrogenation over an oxide semiconductor and identified the activation of the α-C− H bond by the surface oxygen vacancies. The Rh-STO samples prepared by a polymerized complex route (PC) and calcined at different temperatures with 1% Rh doping exhibited a single phase with perovskite structure, when the calcination temperature was >500 °C, although a small amount of graphitic carbon still exists in the sample calcined at 500 °C (Rh-STO-500) (Figure 1a). The presence of perovskite NPs was confirmed by transmission electron microscopy (TEM) (Figure 1c,d), where Pt-loaded Rh-STO-

ompared with the traditional thermal oxidation approaches involving harsh reaction conditions, corrosive reagents, toxic metal catalysts, undesired products, and difficulties in product purification, photocatalytic oxidation provides alternative pathways with mild reaction conditions and environmentally friendly reactants for the oxidation of alcohols,1 inspired by photocatalytic H2 evolution with organic reagents as the sacrificial agent in an aqueous solution.2 So far, extensive efforts have been devoted to the aerobic photocatalytic oxidation of organic compounds by reactive oxygen species using inorganic semiconductors (e.g., TiO2,3−5 CdS,6−8 WO3,9,10 CeO2,11−13 and metal−organic frameworks14) and organic semiconductors.15−18 There has been emerging research interest in the dehydrogenation of alcohols under anaerobic conditions without solvents or in water in the past two years, which is of great importance for potential applications in chemical industry and for H2 production.10,19−23 Zhao and co-workers24 demonstrated a twoelectron transfer mechanism over Pt/TiO2 in the absence of O2 with simultaneous H2 evolution. Ma et al. investigated the mechanism of photocatalytic alcohol dehydrogenation over TiO2 under ultraviolet (UV) light,25 introducing a novel solvent-assisted hole-transfer strategy to prevent overoxidation. Compared with that of TiO2, the oxidation ability of visible light-responsive photocatalysts like carbon nitride, bismuth © XXXX American Chemical Society

Received: March 4, 2019 Accepted: April 11, 2019 Published: April 11, 2019 2075

DOI: 10.1021/acs.jpclett.9b00621 J. Phys. Chem. Lett. 2019, 10, 2075−2080

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Figure 1. (a) XRD patterns of Rh-STO samples calcined at different temperatures. (b) Diffuse reflectance UV−vis spectra of STO and Rh-STO samples calcined at different temperatures. (c) Low-magnification TEM and (d) HRTEM images of Pt (2.6%)-loaded Rh-STO-600.

600 shows STO particles in the range from 20 to 30 nm and deposited Pt NPs with diameters of approximately 2−3 nm (Figure S1). The specific surface area of Rh-STO-600 amounts to 38 m2 g−1, and increasing the calcination temperature led to smaller specific surface areas (Table S1). Diffuse reflectance UV−visible (UV−vis) spectra of undoped STO and Rh-STO samples (Figure 1b) show strong differences in the position of the absorption edges and the absorption peak in the visible light range. The absorption edges of the doped STO samples are shifted significantly to longer wavelengths at approximately 520 and 580 nm. It is also noted that the calcination temperature has a strong influence on the optical properties of the Rh-STO samples due to the different Rh states.31,32 When samples are calcined at ≥800 °C, the absorption peak at 580 nm becomes clearly visible, which can be attributed to the electron transition from the valence band (VB) of SrTiO3 to the unoccupied d states of Rh4+.33 The photoluminescence (PL) peaks (Figure S2) at 560 nm of Rh-STO-800 and RhSTO-900 also confirmed the existence of the mentioned transition, which is absent in other samples.

The VB edges of STO and Rh-STO investigated by XPS are determined to be 2.27 and 1.7 eV (vs NHE) (Figure S3), respectively, in agreement with reported values,34,35 suggesting that Rh doping causes a negative shift of the valence band, thus lowering the band gap. Photocatalytic anaerobic alcohol oxidation was first performed with benzyl alcohol (BA) in an aqueous solution under visible light. We first tried to identify the most active catalyst among the differently calcined samples with the same Pt loading. All of the samples showed highly selective photocatalytic oxidation of BA to benzyl aldehyde with selectivities of >99%. Surprisingly, Rh-STO-600 showed the highest activity, which was almost 10-fold higher than that of Rh-STO-900 (Figure 2a). According to the N2 physisorption measurements (Figure S4 and Table S1), the performance difference is by far not proportional to the specific surface areas of the catalysts. It is important to note that in the absence of Pt, Rh-STO achieved only 4% conversion after irradiation for 6 h (Figure 2b). It was also found that the optimized Pt loading determined by ICP is 2.65 wt % (with an initial Pt amount of 3 wt %) (Figure 2b).36 Figure 2c displays the stable time2076

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Figure 2. (a) Conversion of BA in water over Rh-STO calcined at different temperatures loaded with 3 wt % Pt (initial amount). (b) Conversion of BA in water over Rh-STO-600 loaded with different initial Pt concentrations. Reaction conditions: 0.2 mmol of BA, 25 mg of catalyst, 5 mL of water, Ar, 300 W Xe lamp, visible light (λ > 400 nm), 14 °C, 6 h. (c) Long-term photocatalytic oxidation of BA in a water solution. Reaction conditions: 6 mmol of BA (with 1.2 mmol of DMF as the internal standard), 50 mg of Rh-STO-600 catalyst, 20 mL of water, Ar, 300 W Xe lamp, visible light (λ > 400 nm), 14 °C. (d) Conversion of BA in water over Rh-STO-600 with various scavengers. Reaction conditions: the same as those of panels a and b except with scavengers.

dependent production of benzaldehyde and H2 in the nearly saturated aqueous benzyl alcohol solution (3.24 g in 100 mL of water). The initial rate of benzaldehyde production was 36.1 μmol h−1 with a corresponding H2 evolution of 32.3 μmol h−1. Considering the error in the volumetric H2 measurement, the molar ratio of produced benzaldehyde and H2 was calculated to be ∼1.0, implying stoichiometric H2 evolution and benzaldehyde production. No product was determined in the absence of a photocatalyst or light. Via the addition of ammonium oxalate as a hole scavenger (Figure 2d), the conversion of BA to benzaldehyde dramatically decreased to 15.5%, while the addition of benzoquinone and tert-butyl alcohol as electron and hydroxyl radical scavengers, respectively, did not lead to significant decreases in alcohol conversion. When adding tert-butyl alcohol, we did not find a decreased tert-butyl alcohol concentration or any new products in the chromatogram. It is therefore reasonable to conclude that the photogenerated holes are the active species for the selective oxidation but not O2− or hydroxyl radicals. Oxidation of other alcohols over Rh-STO-600 photocatalysts in water demonstrated the broad scope of the visible light-driven selective conversion (Table 1). All of these aromatic and aliphatic alcohols can be selectively and efficiently oxidized to the corresponding aldehydes and ketones without any detectable acid formation or only traces

Table 1. Photocatalytic Oxidation of Alcohols in an Aqueous Solutiona entry 1 2 3 4 5 6 7 8 9 10 11b

conversion (%)

alcohol

product

benzyl alcohol 4-methylbenzyl alcohol 2-methylbenzyl alcohol 1-phenylethanol cinnamyl alcohol 4-chlorobenzyl alcohol 2-chlorobenzyl alcohol 2-nitrobenzyl alcohol 2-propanol 1-pentanol ethanol

benzyl aldehyde 4methylbenzaldehyde 2methylbenzaldehyde acetophenone cinnamyl aldehyde 4-chlorobenzaldehyde

selectivity (%)

70 62

>99 >99

33

>99

35 41 79

>99 >99 >99

2-chlorobenzaldehyde

35

>99

2-nitrobenzaldehyde

10

>99

acetone pentanal acetaldehyde

20 44 2.1

>99 83 >96

a

Reaction conditions: alcohol (0.2 mmol), water (5 mL), Rh-STO600 (25 mg), Ar, 300 W Xe lamp, visible light (λ > 400 nm), 14 °C, 6 h. bThe same condition as in footnote a except using 8 mmol of ethanol.

of it. It has to be noted that the ortho and para substituent groups have different reactivities in the photooxidation due to 2077

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Figure 3. (a) Cycling performance of pure IPA conversion over Rh-STO-600 with 3 wt % Pt (initial amount). Reaction conditions: 25 mg of catalyst, 5 mL of IPA, Ar, 300 W Xe lamp, visible light (λ > 400 nm), 14 °C. (b) AQE of BA conversion with and without water over Rh-STO-600 with 3 wt % Pt (initial amount). Reaction conditions: BA (0.2 mmol in 5 mL of water or 5 mL of pure BA), catalyst (25 mg), Ar, 300 W Xe lamp, visible light, 14 °C, 6 h.

Figure 4. (a) FTIR spectra of IPA in the gas phase and adsorbed IPA on Rh-STO-600 and Rh-STO-900 at room temperature. For adsorbed IPA on Rh-STO-600 and Rh-STO-900, blue lines represent the spectra from the initial introduction of IPA (1 mbar) and red lines represent those after adsorption had been maintained for 30 min. (b) Schematic illustration of alcohol chemisorption on an oxygen vacancy in the Rh-STO (110) surface. Yellow spheres represent Sr, cyan spheres Ti, red spheres O in STO, purple spheres O in IPA, black spheres C, and gray spheres H.

same conditions (shown in Table 1) was ∼47%, with a selectivity of >99%, indicating that an efficient dehydrogenation cocatalyst is necessary for the reaction. With an increasing calcination temperature, the color of the produced Rh-STO-x becomes more purple, which is also reflected in the UV−vis spectra. This observation suggests that during low-temperature calcination, Rh in the lattice of STO mainly remains Rh3+, while at higher temperatures, Rh3+ is oxidized to Rh4+, which was confirmed by the Rh 3d XPS analysis (Figure S8). Doping of Rh3+ into the lattice of SrTiO3 may induce the generation of oxygen vacancies at the surface, especially in the case of NPs, implying that Rh-STO-600 should contain more oxygen vacancies than Rh-STO-900, which is confirmed by the refinement results of XRD patterns (Figure S9) and electron paramagnetic resonance (EPR) experiments (Figure S10 and Figure S11). To further clarify the function of surface oxygen vacancies, in situ diffuse reflectance infrared Fourier transform (DRIFT) spectra were recorded to investigate isopropyl alcohol (IPA) adsorption on Rh-STO-600 and Rh-STO-900 with IPA as a probe molecule (Figure 4). After the dosing of IPA at 1 mbar, the emerging diagnostic bands at 1131 and 1164 cm−1 can be assigned to υC−O and υC−C of isopropoxy species, respectively,

spatial effects (entries 2 and 3 and entries 6 and 7). We also used methanol in the dehydrogenation reaction. The main product is methyl formate with a trace amount of formaldehyde, indicating that the catalyst can break the strong C− H bond in methanol in visible light. Due to the high chemical reactivity of formaldehyde, the subsequent coupling reaction between formaldehyde and methanol resulted in methyl formate. A quadrupole mass spectrometer (QMS) was used to determine the hydrogen source with D2O as the solvent. Figure S7 shows that the evolved gas was almost completely composed of H2, but not of D2 or HD, indicating that alcohol oxidation actually occurs via dehydrogenation in the presence of water. To exclude possible limitations by mass transfer, pure benzyl alcohol and pure isopropanol (IPA) were applied in the photocatalytic alcohol oxidation reaction. It turned out that the initial oxidation rates of pure IPA were ∼50 μmol h−1 (Figure 3, in the last cycle). The performance was quite stable in the cycling test. The apparent quantum efficiency of pure benzyl alcohol dehydrogenation at 420 nm was ≤49.5%, which was much higher than that in a saturated benzyl alcohol/water solution (19.5%). When Pd NPs instead of Pt NPs were loaded on Rh-STO-600, the resulting conversion of BA under the 2078

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which are quite different from those of the gas phase (1148 and 1083 cm−1, respectively), indicating that IPA adsorbs dissociatively on Lewis sites such as oxygen vacancies on the surface of Rh-STO-600 and Rh-STO-900.37−40 The band at 2970 cm−1 can be assigned to υC−H of both molecularly and dissociatively adsorbed IPA. Comparing the intensity ratio of the bands at 1164 and 1131 cm−1 and the band at 2970 cm−1 for Rh-STO-600 and Rh-STO-900 indicates that the dissociative adsorption of IPA is more favored on Rh-STO600 than on Rh-STO-900. Compared with the υOH band at 3654 cm−1 from free IPA in the gas phase, in the presence of STO substrates, the υOH band is less responsive. After adsorption had been maintained for 30 min, a band at 1707 cm−1 assigned to the υCO vibration of adsorbed acetone emerged as shown in the magnified inset,41,42 which is slightly red-shifted compared with that of gas-phase acetone.43 This observation suggests that traces of acetone can be formed on Rh-STO-600 even without irradiation. However, no obvious formation of acetone was found for Rh-STO-900. The bands at 1574 cm−1 can be ascribed to υCC−O− of the enolate species,41,42 which may originate from side reactions. Therefore, we infer that Rh-STO-600 exhibits higher activity for the dissociative adsorption of IPA and the cleavage of the α-C−H bond compared with that of Rh-STO-900. It is also worth noting that no further photocatalytic oxidation of carbonyl compounds takes place under anaerobic conditions, even in the aqueous solution. Bahnemann et al.44 proposed that the overall oxidation of alcohol involves five steps, where the consecutive steps are more energetically demanding than the formation of carbonyl compounds. Thus, controlling the VB edge position of STO via Rh doping proved to be effective for stopping the oxidation process at the carbonyl compounds. The simulation of the interaction between IPA and SrTiO3 with or without oxygen defects (Figure S12) also indicated that the dissociative adsorption of IPA on defective SrTiO3−x dramatically weakened the α-C−H bond. In summary, we developed Rh-doped SrTiO3 photocatalysts with well-controlled VB edge positions, oxygen vacancies, and Pt cocatalyst loading that achieve efficient conversion of alcohols to aldehydes or ketones under mild conditions with simultaneous H2 evolution under visible light. A high quantum efficiency of 49.5% was achieved for converting pure benzyl alcohol. Importantly, we determined that oxygen vacancies facilitate the α-C−H bond activation under anaerobic conditions kinetically via dissociative alcohol adsorption. This work opens new pathways for improving the selectivity and efficiency of photocatalytic organic transformations.

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Letter

AUTHOR INFORMATION

Corresponding Authors

*E-mail: [email protected]. *E-mail: [email protected]. ORCID

Guixia Zhao: 0000-0003-4537-3508 Shannon A. Bonke: 0000-0002-3285-4356 Yuejie Ai: 0000-0001-6724-0971 Xiangke Wang: 0000-0002-3352-1617 Martin Muhler: 0000-0001-5343-6922 Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS The authors acknowledge funding from the Alexander von Humboldt Foundation, the Max Planck Society (Max Planck Fellowship, IMPRS RECHARGE), and DFG (SFB/TRR 247).

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REFERENCES

(1) Zhang, P.; Gong, Y.; Li, H.; Chen, Z.; Wang, Y. Solvent-free aerobic oxidation of hydrocarbons and alcohols with Pd@N-doped carbon from glucose. Nat. Commun. 2013, 4, 1593. (2) Tong, H.; Ouyang, S.; Bi, Y.; Umezawa, N.; Oshikiri, M.; Ye, J. Nano-photocatalytic materials: Possibilities and challenges. Adv. Mater. 2012, 24, 229−251. (3) Lang, X.; Ma, W.; Chen, C.; Ji, H.; Zhao, J. Selective aerobic oxidation mediated by TiO2 photocatalysis. Acc. Chem. Res. 2014, 47, 355−363. (4) Tsukamoto, D.; Shiraishi, Y.; Sugano, Y.; Ichikawa, S.; Tanaka, S.; Hirai, T. Gold nanoparticles located at the interface of anatase/ rutile TiO2 particles as active plasmonic photocatalysts for aerobic oxidation. J. Am. Chem. Soc. 2012, 134, 6309−6315. (5) Augugliaro, V.; Caronna, T.; Loddo, V.; Marcì, G.; Palmisano, G.; Palmisano, L.; Yurdakal, S. Oxidation of aromatic alcohols in irradiated aqueous suspensions of commercial and home-prepared rutile TiO2: A selectivity study. Chem. - Eur. J. 2008, 14, 4640−4046. (6) Zhang, N.; Zhang, Y.; Pan, X.; Fu, X.; Liu, S.; Xu, Y.-J. Assembly of CdS nanoparticles on the two-dimensional graphene scaffold as visible-light-driven photocatalyst for selective organic transformation under ambient conditions. J. Phys. Chem. C 2011, 115, 23501−23511. (7) Zhang, N.; Liu, S.; Fu, X.; Xu, Y.-J. Fabrication of coenocytic Pd@CdS nanocomposite as a visible light photocatalyst for selective transformation under mild conditions. J. Mater. Chem. 2012, 22, 5042−5052. (8) Chai, Z.; Zeng, T.-T.; Li, Q.; Lu, L.-Q.; Xiao, W.-J.; Xu, D. Efficient visible light-driven splitting of alcohols into hydrogen and corresponding carbonyl compounds over a Ni-modified CdS photocatalyst. J. Am. Chem. Soc. 2016, 138, 10128−10131. (9) Zhang, N.; Li, X.; Ye, H.; Chen, S.; Ju, H.; Liu, D.; Lin, Y.; Ye, W.; Wang, C.; Xu, Q.; et al. Oxide defect engineering enables to couple solar energy into oxygen activation. J. Am. Chem. Soc. 2016, 138, 8928−8935. (10) Tsukamoto, D.; Ikeda, M.; Shiraishi, Y.; Hara, T.; Ichikuni, N.; Tanaka, S.; Hirai, T. Selective photocatalytic oxidation of alcohols to aldehydes in water by TiO2 partially coated with WO3. Chem. - Eur. J. 2011, 17, 9816−9824. (11) Tanaka, A.; Hashimoto, K.; Kominami, H. Preparation of Au/ CeO2 exhibiting strong surface plasmon resonance effective for selective or chemoselective oxidation of alcohols to aldehydes or ketones in aqueous suspensions under irradiation by green light. J. Am. Chem. Soc. 2012, 134, 14526−14533. (12) Chhowalla, M.; Shin, H. S.; Eda, G.; Li, L.-J.; Loh, K. P.; Zhang, H. The chemistry of two-dimensional layered transition metal dichalcogenide nanosheets. Nat. Chem. 2013, 5, 263−275. (13) Tanaka, A.; Hashimoto, K.; Kominami, H. Selective photocatalytic oxidation of aromatic alcoholsto aldehydes in an aqueous

ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.jpclett.9b00621. Experimental procedures, STEM image and EDS images, photoluminescence spectra, XPS−VB spectra, schematic presentation of the apparatus, fitted Rh 3d XP spectra, characteristic parameters of the samples, XRD patterns after refinement of Rh-STO samples, EPR analysis, DFT simulations, and further mechanistic discussion (PDF) 2079

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photocatalyst in Z-scheme overall water splitting under visible light irradiation. Chem. Mater. 2014, 26, 4144−4150. (32) Konta, R.; Ishii, T.; Kato, H.; Kudo, A. Photocatalytic activities of noble metal ion doped SrTiO3 under visible light irradiation. J. Phys. Chem. B 2004, 108, 8992−8995. (33) Yamaguchi, Y.; Usuki, S.; Kanai, Y.; Yamatoya, K.; Suzuki, N.; Katsumata, K.-i.; Terashima, C.; Suzuki, T.; Fujishima, A.; Sakai, H.; et al. Selective inactivation of bacteriophage in the presence of bacteria by use of ground Rh-doped SrTiO3 photocatalyst and visible light. ACS Appl. Mater. Interfaces 2017, 9, 31393−31400. (34) Modak, B.; Ghosh, S. K. Origin of enhanced visible light driven water splitting by (Rh, Sb)-SrTiO3. Phys. Chem. Chem. Phys. 2015, 17, 15274−15283. (35) Fujisawa, J.-i.; Eda, T.; Hanaya, M. Comparative study of conduction-band and valence-band edges of TiO2, SrTiO3, and BaTiO3 by ionization potential measurements. Chem. Phys. Lett. 2017, 685, 23−26. (36) Zhang, G.; Lan, Z.-A.; Wang, X. Surface engineering of graphitic carbon nitride polymers with cocatalysts for photocatalytic overall water splitting. Chem. Sci. 2017, 8, 5261−5274. (37) Kubokawa, Y.; Miyata, H.; Wakamiya, M. Interaction of oxygen with acetone and 2-propanol adsorbed on magnesium oxide. J. Phys. Chem. 1973, 77, 141−142. (38) Miyata, H.; Hata, K.; Nakajima, T.; Kubokawa, Y. Infrared Studies of the Oxidation of 2-Propanol on ZnO. Bull. Chem. Soc. Jpn. 1980, 53, 2401−2402. (39) Popova, G. Y.; Andrushkevich, T.; Chesalov, Y. A.; Stoyanov, E. In situ FTIR Study of the Adsorption of Formaldehyde, Formic Acid, and Methyl Formiate at the Surface of TiO2 (Anatase). Kinet. Catal. 2000, 41, 805−811. (40) Rossi, P. F.; Busca, G.; Lorenzelli, V.; Saur, O.; Lavalley, J. C. Microcalorimetric and FT-IR spectroscopic study of the adsorption of isopropyl alcohol and hexafluoroisopropyl alcohol on titanium dioxide. Langmuir 1987, 3, 52−58. (41) Fouad, N.; Thomasson, P.; Knözinger, H. Surface reactions of acetone, acetylene and methylbutynol on a yttrium-modified magnesium oxide catalyst. Appl. Catal., A 2000, 196, 125−133. (42) Zaki, M.; Hasan, M.; Al-Sagheer, F.; Pasupulety, L. Surface chemistry of acetone on metal oxides: IR observation of acetone adsorption and consequent surface reactions on silica−alumina versus silica and alumina. Langmuir 2000, 16, 430−436. (43) Eda, G.; Yamaguchi, H.; Voiry, D.; Fujita, T.; Chen, M.; Chhowalla, M. Photoluminescence from Chemically Exfoliated MoS2. Nano Lett. 2011, 11, 5111−5116. (44) Kandiel, T. A.; Ivanova, I.; Bahnemann, D. W. Long-term investigation of the photocatalytic hydrogen production on platinized TiO2: an isotopic study. Energy Environ. Sci. 2014, 7, 1420−1425.

suspension of gold nanoparticles supported on cerium(IV) oxide under irradiation of green light. Chem. Commun. 2011, 47, 10446− 10448. (14) Chen, Y.-Z.; Wang, Z. U.; Wang, H.; Lu, J.; Yu, S.-H.; Jiang, H.L. Singlet oxygen-engaged selective photo-oxidation over Pt nanocrystals/porphyrinic MOF: The roles of photothermal effect and Pt electronic state. J. Am. Chem. Soc. 2017, 139, 2035−2044. (15) Huang, W.; Ma, B. C.; Lu, H.; Li, R.; Wang, L.; Landfester, K.; Zhang, K. A. I. Visible-light-promoted selective oxidation of alcohols using a covalent triazine framework. ACS Catal. 2017, 7, 5438−5442. (16) Su, F.; Mathew, S. C.; Lipner, G.; Fu, X.; Antonietti, M.; Blechert, S.; Wang, X. mpg-C3N4-catalyzed selective oxidation of alcohols using O2 and visible light. J. Am. Chem. Soc. 2010, 132, 16299−16301. (17) Su, F.; Mathew, S. C.; Möhlmann, L.; Antonietti, M.; Wang, X.; Blechert, S. Aerobic oxidative coupling of amines by carbon nitride photocatalysis with visible light. Angew. Chem., Int. Ed. 2011, 50, 657− 660. (18) Wang, Y.; Zhang, J.; Wang, X.; Antonietti, M.; Li, H. Boronand fluorine-containing mesoporous carbon nitride polymers: Metalfree catalysts for cyclohexane oxidation. Angew. Chem., Int. Ed. 2010, 49, 3356−3359. (19) Zhang, Y.; Zhang, N.; Tang, Z.-R.; Xu, Y.-J. Identification of Bi2WO6 as a highly selective visible-light photocatalyst toward oxidation of glycerol to dihydroxyacetone in water. Chem. Sci. 2013, 4, 1820−1824. (20) Li, F.; Wang, Y.; Du, J.; Zhu, Y.; Xu, C.; Sun, L. Simultaneous oxidation of alcohols and hydrogen evolution in a hybrid system under visible light irradiation. Appl. Catal., B 2018, 225, 258−263. (21) Meng, S.; Ning, X.; Chang, S.; Fu, X.; Ye, X.; Chen, S. Simultaneous dehydrogenation and hydrogenolysis of aromatic alcohols in one reaction system via visible-light-driven heterogeneous photocatalysis. J. Catal. 2018, 357, 247−256. (22) Meng, S.; Ye, X.; Zhang, J.; Fu, X.; Chen, S. Effective use of photogenerated electrons and holes in a system: Photocatalytic selective oxidation of aromatic alcohols to aldehydes and hydrogen production. J. Catal. 2018, 367, 159−170. (23) Zhang, L.; Jiang, D.; Irfan, R. M.; Tang, S.; Chen, X.; Du, P. Highly efficient and selective photocatalytic dehydrogenation of benzyl alcohol for simultaneous hydrogen and benzaldehyde production over Ni-decorated Zn0.5Cd0.5S solid solution. J. Energy Chem. 2019, 30, 71−77. (24) Zhang, M.; Wang, Q.; Chen, C.; Zang, L.; Ma, W.; Zhao, J. Oxygen atom transfer in the photocatalytic oxidation of alcohols by TiO2: Oxygen isotope studies. Angew. Chem., Int. Ed. 2009, 48, 6081− 6084. (25) Ma, D.; Liu, A.; Lu, C.; Chen, C. Photocatalytic dehydrogenation of primary alcohols: Selectivity goes against adsorptivity. ACS Omega 2017, 2, 4161−4172. (26) Liu, J.; Yuan, Q.; Zhao, H.; Zou, S. Efficient room-temperature selective oxidation of benzyl alcohol into benzaldehyde over Pt/ BiOCl nanocomposite. Catal. Lett. 2018, 148, 1093−1099. (27) Bellardita, M.; García-López, E. I.; Marcì, G.; Krivtsov, I.; García, J. R.; Palmisano, L. Selective photocatalytic oxidation of aromatic alcohols in water by using P-doped g-C3N4. Appl. Catal., B 2018, 220, 222−233. (28) Zheng, C.; He, G.; Xiao, X.; Lu, M.; Zhong, H.; Zuo, X.; Nan, J. Selective photocatalytic oxidation of benzyl alcohol into benzaldehyde with high selectivity and conversion ratio over Bi4O5Br2 nanoflakes under blue LED irradiation. Appl. Catal., B 2017, 205, 201−210. (29) Marcì, G.; García-López, E.; Palmisano, L. Polymeric carbon nitride (C3N4) as heterogeneous photocatalyst for selective oxidation of alcohols to aldehydes. Catal. Today 2018, 315, 126−137. (30) Xiao, X.; Zheng, C.; Lu, M.; Zhang, L.; Liu, F.; Zuo, X.; Nan, J. Deficient Bi24O31Br10 as a highly efficient photocatalyst for selective oxidation of benzyl alcohol into benzaldehyde under blue LED irradiation. Appl. Catal., B 2018, 228, 142−151. (31) Wang, Q.; Hisatomi, T.; Ma, S. S. K.; Li, Y.; Domen, K. Core/ shell structured La- and Rh-codoped SrTiO3 as a hydrogen evolution 2080

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