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Chinese Journal of Catalysis
2021, Vol. 42, No. 9
Online: 18 September 2021

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Cover: Dr. Tan and coworkers in their article on pages 1451–1458 reported a robust oxygen-related reaction (ORR and OER) electrocatalyst by combining the spinel iron-cobalt oxide and nitrogen-doped ordered mesoporous carbon (NOMC) through one-step hard template method. The illustration shows the molecular structure of the catalyst, and the zinc-air battery model with the catalyst as air electrode.

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Recent advances on Bi2WO6-based photocatalysts for environmental and energy applications Tong Chen, Lizhen Liu, Cheng Hu, Hongwei Huang 2021, 42 (9):  1413-1438.  DOI: 10.1016/S1872-2067(20)63769-X Abstract ( 657 )   HTML ( 291 )   PDF (7767KB) ( 1502 )   Bismuth tungstate (Bi2WO6) has become a research hotspot due to its potential in photocatalytic energy conversion and environmental purification. Nevertheless, the limited light absorption and fast recombination of photogenerated carriers hinder the further improvement of the photocatalytic performance of Bi2WO6. Herein, we provide a systematic review for the recent advances on Bi2WO6-based photocatalysts. It starts with the crystal structure, optical properties and photocatalytic fundamentals of Bi2WO6. Then, we focus on the modification strategies of Bi2WO6 based on morphology control, atomic modulation and composite fabrication for diverse photocatalytic applications, such as organic synthesis, water splitting, CO2 reduction, water treatment, air purification, bacterial inactivation, etc. Finally, some current challenges and future development prospects are proposed. We expect that this review can provide a useful reference and guidance for the development of efficient Bi2WO6 photocatalysts.

Communications

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Alkali metal cation effects on electrocatalytic CO2 reduction with iron porphyrins Kai Guo, Haitao Lei, Xialiang Li, Zongyao Zhang, Yabo Wang, Hongbo Guo, Wei Zhang, Rui Cao 2021, 42 (9):  1439-1444.  DOI: 10.1016/S1872-2067(20)63762-7 Abstract ( 432 )   HTML ( 36 )   PDF (2005KB) ( 650 )   Supporting Information The electrocatalytic CO2 reduction reaction (CO2RR) has attracted increasing attention in recent years. Practical electrocatalysis of CO2RR must be carried out in aqueous solutions containing electrolytes of alkali metal cations such as sodium and potassium. Although considerable efforts have been made to design efficient electrocatalysts for CO2RR and to investigate the structure-activity relationships using molecular model complexes, only a few studies have been investigated the effect of alkali metal cations on electrocatalytic CO2RR. In this study, we report the effect of alkali metal cations (Na+ and K+) on electrocatalytic CO2RR with Fe porphyrins. By running CO2RR electrocatalysis in dimethylformamide (DMF), we found that the addition of Na+ or K+ considerably improves the catalytic activity of Fe chloride tetrakis(3,4,5-trimethoxyphenyl)porphyrin (FeP). Based on this result, we synthesized an Fe porphyrin N18C6-FeP bearing a tethered 1-aza-18-crown-6-ether (N18C6) group at the second coordination sphere of the Fe site. We showed that with the tethered N18C6 to bind Na+ or K+, N18C6-FeP is more active than FeP for electrocatalytic CO2RR. This work demonstrates the positive effect of alkali metal cations to improve CO2RR electrocatalysis, which is valuable for the rational design of new efficient catalysts.

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Sustainable electrochemical cross-dehydrogenative coupling of 4-quinolones and diorganyl diselenides Jin-Yang Chen, Hong-Yu Wu, Qing-Wen Gui, Shan-Shu Yan, Jie Deng, Ying-Wu Lin, Zhong Cao, Wei-Min He 2021, 42 (9):  1445-1450.  DOI: 10.1016/S1872-2067(20)63750-0 Abstract ( 185 )   HTML ( 11 )   PDF (945KB) ( 127 )   Supporting Information An environmentally friendly method for the synthesis of 3-organylselenyl quinolones through the electrochemical cross-dehydrogenative coupling of 4-quinolones and diorganyl diselenides was developed. As a green, atom economic and self-separating process, the present reaction requires neither external oxidants nor electrolytes, forming a recyclable catalytic system.

Articles

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Efficient spinel iron-cobalt oxide/nitrogen-doped ordered mesoporous carbon catalyst for rechargeable zinc-air batteries He-lei Wei, Ai-dong Tan, Shu-zhi Hu, Jin-hua Piao, Zhi-yong Fu 2021, 42 (9):  1451-1458.  DOI: 10.1016/S1872-2067(20)63752-4 Abstract ( 331 )   HTML ( 21 )   PDF (4045KB) ( 311 )   Supporting Information A robust oxygen-related electrocatalyst, composed of spinel iron-cobalt oxide and nitrogen-doped ordered mesoporous carbon (NOMC), was developed for rechargeable metal-air batteries. Electrochemical tests revealed that the optimal catalyst Fe0.5Co/NOMC exhibits superior activity with a half-wave potential of 0.89 V (vs. reversible hydrogen electrode) for the oxygen reduction reaction and an overpotential of 0.31 V at 10 mA cm-2 for the oxygen evolution reaction. For demonstration, the catalyst was used in the assembly of a rechargeable zinc-air battery, which exhibited an exceptionally high energy density of 820 Wh kg-1 at 100 mA cm-2, a high power density of 153 mW cm-2at 1.0 V, and superior cycling stability up to 432 cycles (144 h) under ambient air.

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Solar energy-driven C-H activation of methanol for direct C-C coupling to ethylene glycol with high stability by nitrogen doped tantalum oxide Limei Wang, Daxue Du, Biao Zhang, Shunji Xie, Qinghong Zhang, Haiyan Wang, Ye Wang 2021, 42 (9):  1459-1467.  DOI: 10.1016/S1872-2067(21)63797-X Abstract ( 383 )   HTML ( 22 )   PDF (2834KB) ( 239 )   Supporting Information Direct photocatalytic coupling of methanol to ethylene glycol (EG) is highly attractive. The reported photocatalysts for this reaction are all metal sulfide semiconductors, which may suffer from photocorrosion and have low stability. Thus, the development of non-sulfide photocatalysts for efficient photocatalytic coupling of methanol to EG and H2 with high stability is urgent but extremely challenging. Herein, the first metal oxide photocatalyst, tantalum-based semiconductor, is reported for preferential activation of C-H bond within methanol to form hydroxymethyl radical (•CH2OH) and subsequent C-C coupling to EG. Compared with other metal oxide photocatalysts, such as TiO2, ZnO, WO3, Nb2O5, tantalum oxide (Ta2O5) is unique in that it can realize the selective photocatalytic coupling of methanol to EG. The co-catalyst free nitrogen doped tantalum oxide (2%N-Ta2O5) shows an EG formation rate as high as 4.0 mmol gcat-1 h-1, about 9 times higher than that of Ta2O5, with a selectivity higher than 70%. The high charge separation ability of nitrogen doped tantalum oxide plays a key role in its high activity for EG production. This catalyst also shows excellent stability longer than 160 h, which has not been achieved over the reported metal sulfide photocatalysts. Tantalum-based photocatalyst is an environmentally friendly and highly stable candidate for photocatalytic coupling of methanol to EG.

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Organic-free synthesis of MOR nanoassemblies with excellent DME carbonylation performance Kaipeng Cao, Dong Fan, Shu Zeng, Benhan Fan, Nan Chen, Mingbin Gao, Dali Zhu, Linying Wang, Peng Tian, Zhongmin Liu 2021, 42 (9):  1468-1477.  DOI: 10.1016/S1872-2067(20)63777-9 Abstract ( 259 )   HTML ( 19 )   PDF (2342KB) ( 311 )   Supporting Information Seed-assisted low alkalinity gel system was developed to explore the organic-free synthesis of MOR zeolite. MOR nanoassemblies with Si/Al ratio (SAR) up to 9.4 and high solid yield (84-94%) were successfully obtained under controlled low alkalinity conditions. Characterization results demonstrate that the acid strength increases in parallel with the SAR, while the total acid amount and the proton distribution in the main channels and the side pockets are similar for the samples. The proton distribution in the H-MOR is not straightforwardly related to the Na+ distribution in the as-synthesized MOR, implying the transfer of the protons among the oxygen sites of framework T atom. Relative to low-silica samples I-5.3 and I-7.4, sample I-9.4 displays the best mass transfer performance and accessibility of the acid sites by pyridine due to its relatively low Al density and mild dealumination degree. Correspondingly, sample I-9.4 (pyridine-modified catalyst) shows the best activity with ca. 100% selectivity of methyl acetate (MAc) in the DME carbonylation reaction. The high steady MAc yield (6.8 mmol/g/h) over sample I-9.4 suggests the promising application of MOR nanoassemblies synthesized by this economical organic-free strategy.

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Hot-electron-assisted S-scheme heterojunction of tungsten oxide/graphitic carbon nitride for broad-spectrum photocatalytic H2 generation Qinqin Liu, Xudong He, Jinjun Peng, Xiaohui Yu, Hua Tang, Jun Zhang 2021, 42 (9):  1478-1487.  DOI: 10.1016/S1872-2067(20)63753-6 Abstract ( 269 )   HTML ( 15 )   PDF (5447KB) ( 376 )   Supporting Information Extended light absorption and dynamic charge separation are vital factors that determine the effectiveness of photocatalysts. In this study, a nonmetallic plasmonic S-scheme photocatalyst was fabricated by loading 1D plasmonic W18O49 nanowires onto 2D g-C3N4 nanosheets. W18O49 nanowires play the dual role of a light absorption antenna—that extends light adsorption—and a hot electron donor—that assists the water reduction reaction in a wider light spectrum range. Moreover, S-scheme charge transfer resulting from the matching bandgaps of W18O49 and g-C3N4 can lead to strong redox capability and high migration speed of the photoinduced charges. Consequently, in this study, W18O49/g-C3N4 hybrids exhibited higher photocatalytic H2 generation than that of pristine g-C3N4 under light irradiation of 420-550 nm. Furthermore, the H2 production rate of the best-performing W18O49/g-C3N4 hybrid was 41.5 μmol·g-1·h-1 upon exposure to monochromatic light at 550 nm, whereas pure g-C3N4 showed negligible activity. This study promotes novel and environmentally friendly hot-electron-assisted S-scheme photocatalysts for the broad-spectrum utilization of solar light.

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Effects of different methods of introducing Mo on denitration performance and anti-SO2 poisoning performance of CeO2 Lulu Li, Chengyan Ge, Jiawei Ji, Wei Tan, Xin Wang, Xiaoqian Wei, Kai Guo, Changjin Tang, Lin Dong 2021, 42 (9):  1488-1499.  DOI: 10.1016/S1872-2067(20)63778-0 Abstract ( 199 )   HTML ( 21 )   PDF (1351KB) ( 147 )   Cerium-based catalysts are very attractive for the catalytic abatement of nitrogen oxides (NOx) emitted from stationary sources. However, the main challenge is still achieving satisfactory catalytic activity in the low-temperature range and tolerance to SO2 poisoning. In the present work, two series of Mo-modified CeO2 catalysts were respectively obtained through a wet impregnation method (Mo-CeO2) and a co-precipitation method (MoCe-cp), and the roles of the Mo species were systematically investigated. Activity tests showed that the Mo-CeO2 catalyst displayed much higher NO conversion at low temperature and anti-SO2 ability than MoCe-cp. The optimal Mo-CeO2 catalyst displayed over 80% NO elimination efficiency even at 150 °C and remarkable SO2 resistance at 250 °C (nearly no activity loss after 40 h test). The characterization results indicated that the introduced Mo species were highly dispersed on the Mo-CeO2 catalyst surface, thereby providing more Brønsted acid sites and inhibiting the formation of stable adsorbed NOx species. These factors synergistically promote the selective catalytic reduction (SCR) reaction in accordance with the Eley-Rideal (E-R) reaction path on the Mo-CeO2 catalyst. Additionally, the molybdenum surface could protect CeO2 from SO2 poisoning; thus, the reducibility of the Mo-CeO2 catalyst declined slightly to an adequate level after sulfation. The results in this work indicate that surface modification with Mo species may be a simple method of developing highly efficient cerium-based SCR catalysts with superior SO2 durability.

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Tuning the intermediate reaction barriers by a CuPd catalyst to improve the selectivity of CO2 electroreduction to C2 products Li Zhu, Yiyang Lin, Kang Liu, Emiliano Cortés, Hongmei Li, Junhua Hu, Akira Yamaguchi, Xiaoliang Liu, Masahiro Miyauchi, Junwei Fu, Min Liu 2021, 42 (9):  1500-1508.  DOI: 10.1016/S1872-2067(20)63754-8 Abstract ( 499 )   HTML ( 40 )   PDF (2908KB) ( 629 )   Supporting Information Electrochemical CO2 reduction is a promising strategy for the utilization of CO2 and intermittent excess electricity. Cu is the only single metal catalyst that can electrochemically convert CO2 into multicarbon products. However, Cu exhibits an unfavorable activity and selectivity for the generation of C2 products because of the insufficient amount of CO* provided for the C-C coupling. Based on the strong CO2 adsorption and ultrafast reaction kinetics of CO* formation on Pd, an intimate CuPd(100) interface was designed to lower the intermediate reaction barriers and improve the efficiency of C2 product formation. Density functional theory (DFT) calculations showed that the CuPd(100) interface enhanced the CO2 adsorption and decreased the CO2* hydrogenation energy barrier, which was beneficial for the C-C coupling. The potential-determining step (PDS) barrier of CO2 to C2 products on the CuPd(100) interface was 0.61 eV, which was lower than that on Cu(100) (0.72 eV). Encouraged by the DFT calculation results, the CuPd(100) interface catalyst was prepared by a facile chemical solution method and characterized by transmission electron microscopy. CO2 temperature-programmed desorption and gas sensor experiments further confirmed the enhancement of the CO2 adsorption and CO2* hydrogenation ability of the CuPd(100) interface catalyst. Specifically, the obtained CuPd(100) interface catalyst exhibited a C2 Faradaic efficiency of 50.3% ± 1.2% at ‒1.4 VRHE in 0.1 M KHCO3, which was 2.1 times higher than that of the Cu catalyst (23.6% ± 1.5%). This study provides the basis for the rational design of Cu-based electrocatalysts for the generation of multicarbon products by fine-tuning the intermediate reaction barriers.

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Enzyme-like mechanism of selective toluene oxidation to benzaldehyde over organophosphoric acid-bonded nano-oxides Changshun Deng, Yun Cui, Junchao Chen, Teng Chen, Xuefeng Guo, Weijie Ji, Luming Peng, Weiping Ding 2021, 42 (9):  1509-1518.  DOI: 10.1016/S1872-2067(20)63758-5 Abstract ( 228 )   HTML ( 8 )   PDF (2330KB) ( 222 )   Supporting Information The completely selective oxidation of toluene to benzaldehyde with dioxygen, without the need to use H2O2, halogens, or any radical initiators, is a reaction long desired but never previously successful. Here, we demonstrate the enzyme-like mechanism of the reaction over hexadecylphosphate acid (HDPA)-bonded nano-oxides, which appear to interact with toluene through specific recognition. The active sites of the catalyst are related to the ability of HDPA to change its bonding to the oxides between monodentate and bidentate during the reaction cycle. This greatly enhances the mobility of the crystal oxygen or the reactivity of the catalyst, specifically in toluene transformations. The catalytic cycle of the catalyst is similar to that of methane monooxygenase. In the presence of catalyst and through O2 oxidation, the conversion of toluene to benzaldehyde is initiated at 70 °C. We envision that this novel mechanism reveals alternatives for an attractive route to design high-performance catalysts with bioinspired structures.

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Novel S-scheme 2D/2D BiOBr/g-C3N4 heterojunctions with enhanced photocatalytic activity Bin Zhang, Xiaoyun Hu, Enzhou Liu, Jun Fan 2021, 42 (9):  1519-1529.  DOI: 10.1016/S1872-2067(20)63765-2 Abstract ( 317 )   HTML ( 25 )   PDF (4056KB) ( 574 )   Supporting Information The design and construction of heterojunction photocatalysts, which possess a staggered energy band structure and appropriate interfacial contact, is an effective way to achieve outstanding photocatalytic performance. In this study, 2D/2D BiOBr/g-C3N4 heterojunctions were successfully obtained by a convenient in situ self-assembly route. Under simulated sunlight irradiation, 99% of RhB (10 mg·L-1, 100 mL) was efficiently degraded by 1.5-BiOBr/g-C3N4 within 30 min, which is better than the performance of both BiOBr and g-C3N4, and it has superior stability. In addition, the composite also exhibits enhanced photocatalytic activity for H2 production. The enhanced activity can be attributed to the intimate interface contact, the larger surface area, and the highly efficient separation of photoinduced electron-hole pairs. Based on the experimental results, a novel S-scheme model was proposed to illuminate the transfer process of charge carriers. This study presents a simple way to develop novel step-scheme photocatalysts for environmental and related applications.

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Strong metal-support interaction boosting the catalytic activity of Au/TiO2 in chemoselective hydrogenation Feng Hong, Shengyang Wang, Junying Zhang, Junhong Fu, Qike Jiang, Keju Sun, Jiahui Huang 2021, 42 (9):  1530-1537.  DOI: 10.1016/S1872-2067(20)63763-9 Abstract ( 266 )   HTML ( 16 )   PDF (1204KB) ( 213 )   Supporting Information Gold catalysts have been reported as highly effective catalysts in various oxidation reactions. However, for chemoselective hydrogenation reactions, gold-based catalysts normally show much lower catalytic activity than platinum group metals, even though their selectivities are excellent. Here, we report that the chemoselective hydrogenation activity of 3-nitrostyrene to 3-vinylaniline over Au/TiO2 can be enhanced up to 3.3 times through the hydrogen reduction strategy. It is revealed that strong metal-support interaction, between gold nanoparticles (NPs) and TiO2 support, is introduced through hydrogen reduction, resulting in partial dispersion of reduced TiOx on the Au surface. The partially covered Au not only increases the perimeter of the interface between the gold NPs and the support, but also benefits H2 activation. Reaction kinetic analysis and H2-D2 exchange reaction show that H2 activation is the critical step in the hydrogenation of 3-nitrostyrene to 3-vinylaniline. Density functional theory calculations verify that hydrogen dissociation and hydrogen transfer are favored at the interface of gold NPs and TiO2 over the hydrogen-reduced Au/TiO2. This study provides insights for fabricating highly active gold-based catalysts for chemoselective hydrogenation reactions.

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Thermo-driven photocatalytic CO reduction and H2 oxidation over ZnO via regulation of reactant gas adsorption electron transfer behavior Zhongming Wang, Hong Wang, Xiaoxiao Wang, Xun Chen, Yan Yu, Wenxin Dai, Xianzhi Fu 2021, 42 (9):  1538-1552.  DOI: 10.1016/S1872-2067(20)63760-3 Abstract ( 173 )   HTML ( 91 )   PDF (2174KB) ( 259 )   Supporting Information Photothermal catalysis is a widely researched field in which the reaction mechanism is usually investigated based on the photochemical behavior of the catalytic material. Considering that the adsorption of reactants is essential for catalytic reactions to occur, in this study, the synergistic effect of photothermal catalysis is innovatively elucidated in terms of the electron transfer behavior of reactant adsorption. For the H2 + O2 or CO + H2 reaction systems over a ZnO catalyst, UV irradiation at 25 °C or heat without UV irradiation did not cause H2 oxidation or CO reduction; only photothermal conditions (100 or 150 °C + UV light) initiated the two reactions. This result is related to the electron transfer behavior associated with the adsorption of CO or H2 on ZnO, in which H2 or CO that lost an electron could be oxidized by O2 or hydroxyls. However, the electron-accepting CO could be reduced by the electron-donating H2 into CH4 under photothermal conditions. Based on the in-situ characterization and theoretical calculation results, it was established that the synergistic effect of the photothermal conditions acted on the (002) crystal surface of ZnO to stimulate the growth of zinc vacancies, which resulted in the formation of defect energy levels, adsorption sites, and an adjusted Fermi level. As a result, the electron transfer behavior between adsorbed CO or H2 and the crystal surface varied, which further affected the photocatalytic behavior. The results show that the effect of photothermal synergy may not only produce the expected kinetic energy, but more importantly, produce energy that can change the activation mode of the reactant gas. This study provides a new understanding of the CO catalytic oxidation and reduction processes over semiconductor materials.

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Single crystal metal-organic framework constructed by vertically self-pillared nanosheets and its derivative for oriented lithium plating Xiaomin Jia, Shaowen Li, Tu Sun, Yanzhi Wang, Yaqi Fan, Chaochao Zhang, Yang Xu, Zuozhong Liang, Haitao Lei, Wei Zhang, Yuye Zhou, Yanhang Ma, Haoquan Zheng, Yue Ma, Rui Cao 2021, 42 (9):  1553-1560.  DOI: 10.1016/S1872-2067(20)63755-X Abstract ( 209 )   HTML ( 9 )   PDF (3034KB) ( 510 )   Supporting Information This vertically self-pillared (VSP) structure extends the application range of traditional porous materials with facile mass/ion transport and enhanced reaction kinetics. Here, we prepare a single crystal metal-organic framework (MOF), employing the ZIF-67 structure as a proof of concept, which is constructed by vertically self-pillared nanosheets (VSP-MOF). We further converted VSP-MOF into VSP-cobalt sulfide (VSP-CoS2) through a sulfidation process. Catalysis plays an important role in almost all battery technologies; for metallic batteries, lithium anodes exhibit a high theoretical specific capacity, low density, and low redox potential. However, during the half-cell reaction (Li++e=Li), uncontrolled dendritic Li penetrates the separator and solid electrolyte interphase layer. When employed as a composite scaffold for lithium metal deposition, there are many advantage to using this framework: 1) the VSP-CoS2 substrate provides a high specific surface area to dissipate the ion flux and mass transfer and acts as a pre-catalyst, 2) the catalytic Co center favors the charge transfer process and preferentially binds the Li+ with the enhanced electrical fields, and 3) the VSP structure guides the metallic propagation along the nanosheet 2D orientation without the protrusive dendrites. All these features enable the VSP structure in metallic batteries with encouraging performances.

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Structured binder-free MWW-type titanosilicate with Si-rich shell for selective and durable propylene epoxidation Jinpeng Yin, Xin Jin, Hao Xu, Yejun Guan, Rusi Peng, Li Chen, Jingang Jiang, Peng Wu 2021, 42 (9):  1561-1575.  DOI: 10.1016/S1872-2067(20)63759-7 Abstract ( 278 )   HTML ( 9 )   PDF (2974KB) ( 263 )   Supporting Information Selective and durable fixed-bed catalysts are highly desirable for developing eco-efficient HPPO (hydrogen peroxide propylene oxide) process. The powder titanosilicate catalysts must be shaped before being applied in industrial processes. As the essential additives for preparing formed catalysts, binders are usually the catalytically inert components, but they would cover the surface and pore mouth of zeolite, thereby declining the accessibility of active sites. By recrystallizing the binder (silica)/Ti-MWW extrudates with the assistance of dual organic structure-directing agents, the silica binder was converted into MWW zeolite phase to form a structured binder-free Ti-MWW zeolite with Si-rich shell, which enhanced the diffusion efficiency and maintained the mechanical strength. Meanwhile, due to the partial dissolution of Si in the Ti-MWW matrix, abundant silanol nests formed and part of framework TiO4 species were transferred into open TiO6 ones, improving the accumulation and activation ability of H2O2 inside the monolith. Successive piperidine treatment and fluoridation of the binder-free Ti-MWW further enhanced the H2O2 activation and oxygen transfer ability of the active Ti sites, and stabilized the Ti-OOH intermediate through hydrogen bond formed between the end H in Ti-OOH and the adjacent Si-F species, thus achieving a more efficient epoxidation process. Additionally, the side reaction of PO hydrolysis was inhibited because the modification effectively quenched numerous Si-OH groups. The lifetime of the modified binder-free Ti-MWW catalyst was 2400 h with the H2O2 conversion and PO selectivity both above 99.5%.

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Development of efficient solid chiral catalysts with designable linkage for asymmetric transfer hydrogenation of quinoline derivatives Yiqi Ren, Lin Tao, Chunzhi Li, Sanjeevi Jayakumar, He Li, Qihua Yang 2021, 42 (9):  1576-1585.  DOI: 10.1016/S1872-2067(20)63764-0 Abstract ( 149 )   HTML ( 5 )   PDF (1678KB) ( 261 )   Supporting Information Developing chiral solid catalysts for asymmetric catalysis is desirable for the elimination of homogeneous catalysis flaws but remains an immense challenge. Herein, we report the immobilization of TsDPEN on SBA-15 with an ionic liquid (IL) linkage via the one-pot reaction of imidazole-TsDPEN-N-Boc with 3-(trimethoxysilyl)propyl bromide in the SBA-15 mesopores. After coordination to Rh, the chiral solid catalysts could efficiently catalyze quinoline transfer hydrogenation, achieving 97% conversion with 93% ee, which was comparable to their homogeneous counterparts. The chiral solid catalyst with the IL linkage afforded much higher turnover frequency than that without the IL linkage (93 h-1 vs. 33 h-1), attributed to the phase transfer and formate-enriching ability of the IL linkage. Furthermore, the effect of the pH on the reaction rate of the solid catalyst was investigated, preventing reaction rate retardation during the catalytic process. The tuning of the linkage group is an efficient approach for catalytic activity improvement of immobilized chiral catalysts.

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Electronic and steric factors for enhanced selective synthesis of 2-ethyl-1-hexanol in the Ir-complex-catalyzed Guerbet reaction of 1-butanol Zhanwei Xu, Peifang Yan, Changhui Liang, Songyan Jia, Xiumei Liu, Z. Conrad Zhang 2021, 42 (9):  1586-1592.  DOI: 10.1016/S1872-2067(20)63772-X Abstract ( 215 )   HTML ( 8 )   PDF (1004KB) ( 273 )   Supporting Information 1-Butanol is a potential bio-based fermentation product obtained from cellulosic biomass. As a value-added chemical, 2-ethyl-1-hexanol (2-EH) can be produced by Guerbet conversion from 1-butanol. This work reports the enhanced catalytic Guerbet reaction of 1-butanol to 2-EH by a series of Cp*Ir complexes (Cp*: 1,2,3,4,5-pentamethylcyclopenta-1,3-diene) coordinated to bipyridine-type ligands bearing an ortho-hydroxypyridine group with an electron-donating group and a Cl- anion. The catalytic activity of the Cp*Ir complex increased by increasing the electron density of the bipyridine ligand when functionalized with the para-NMe2 and ortho-hydroxypyridine groups. A record turnover number of 14047 was attained. A mechanistic study indicated that the steric effect of the ethyl group on the α-C of 2-ethylhexanal (2-EHA) and the conjugation effect of C=C-C=O in 2-ethylhex-2-enal (2-EEA) benefits the high selectivity of 2-EH from 1-butanol by inhibiting the cross-aldol reaction of 2-EHA and 2-EEA with butyraldehyde. Nuclear magnetic resonance study revealed the formation of a carbonyl group in the bipyridine-type ligand via the reaction of the Cp*Ir complex with KOH.

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Catalytic C2 prenylation of unprotected indoles: Late-stage diversification of peptides and two-step total synthesis of tryprostatin B Yan-Cheng Hu, Ying Li, Ding-Wei Ji, Heng Liu, Hao Zheng, Gong Zhang, Qing-An Chen 2021, 42 (9):  1593-1607.  DOI: 10.1016/S1872-2067(20)63780-9 Abstract ( 275 )   HTML ( 12 )   PDF (1297KB) ( 147 )   Supporting Information C2 prenylated indoles are widespread in a variety of bioactive natural alkaloids. Therefore, the selective installation of prenyl group at C2 position of NH indoles is of great significance. However, the known protocols generally require a multi-step procedure and stoichiometric promoters. Herein we develop a one-step C2 prenylation of NH indole with cheap tert-prenyl alcohol enabled by acid catalysis. Salient features include good regioselectivity, step- and atom-economy, broad substrate scope, and simple catalytic system. The mechanistic investigations demonstrate that both C2 prenylation and C3 prenylation/migration pathways are engaged in the reaction. Notably, this practical strategy can be applied to the late-stage diversification of tryptophan-based peptides and concise synthesis of tryprostatin B.

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Construction of efficient active sites through cyano-modified graphitic carbon nitride for photocatalytic CO2 reduction Fang Li, Xiaoyang Yue, Haiping Zhou, Jiajie Fan, Quanjun Xiang 2021, 42 (9):  1608-1616.  DOI: 10.1016/S1872-2067(20)63776-7 Abstract ( 742 )   HTML ( 48 )   PDF (7350KB) ( 486 )   Supporting Information The active site amount of photocatalysts, being the key factors in photocatalytic reactions, directly affects the photocatalytic performance of the photocatalyst. Pristine graphitic carbon nitride (g-C3N4) exhibits moderate photocatalytic activity due to insufficient active sites. In this study, cyano-modified porous g-C3N4 nanosheets (MCN-0.5) were synthesized through molecular self-assembly and alkali-assisted strategies. The cyano group acted as the active site of the photocatalytic reaction, because the good electron-withdrawing property of the cyano group promoted carrier separation. Benefiting from the effect of the active sites, MCN-0.5 exhibited significantly enhanced photocatalytic activity for CO2 reduction under visible light irradiation. Notably, the photocatalytic activity of MCN-0.5 was significantly reduced when the cyano groups were removed by hydrochloric acid (HCl) treatment, further verifying the role of cyano groups as active sites. The photoreduction of Pt nanoparticles provided an intuitive indication that the introduction of cyano groups provided more active sites for the photocatalytic reaction. Furthermore, the controlled experiments showed that g-C3N4 grafted with cyano groups using melamine as the precursor exhibited enhanced photocatalytic activity, which proved the versatility of the strategy for enhancing the activity of g-C3N4 via cyano group modification. In situ diffuse reflectance infrared Fourier transform spectroscopy and theoretical calculations were used to investigate the mechanism of enhanced photocatalytic activity for CO2 reduction by cyano-modified g-C3N4. This work provides a promising route for promoting efficient solar energy conversion by designing active sites in photocatalysts.

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Reaction kinetics and phase behavior in the chemoselective hydrogenation of 3-nitrostyrene over Co-N-C single-atom catalyst in compressed CO2 Dan Zhou, Leilei Zhang, Wengang Liu, Gang Xu, Ji Yang, Qike Jiang, Aiqin Wang, Jianzhong Yin 2021, 42 (9):  1617-1624.  DOI: 10.1016/S1872-2067(20)63785-8 Abstract ( 267 )   HTML ( 97 )   PDF (1867KB) ( 245 )   Single-atom catalysts (SACs) have demonstrated excellent performances in chemoselective hydrogenation reactions. However, the employment of precious metals and/or organic solvents compromises their sustainability. Herein, we for the first time report the chemoselective hydrogenation of 3-nitrostyrene over noble-metal-free Co-N-C SAC in green solvent — compressed CO2. An interesting inverted V-curve relation is observed between the catalytic activity and CO2 pressure, where the conversion of 3-nitrostyrene reaches the maximum of 100% at 5.0 MPa CO2 (total pressure of 8.1 MPa). Meanwhile, the selectivities to 3-vinylaniline at all pressures remain high (> 99%). Phase behavior studies reveal that, in sharp contrast with the single phase which is formed at total pressure above 10.8 MPa, bi-phase composed of CO2/H2 gas-rich phase and CO2-expanded substrate liquid phase forms at total pressure of 8.1 MPa, which dramatically changes the reaction kinetics of the catalytic system. The reaction order with respect to H2 pressure decreases from ~0.5 to zero at total pressure of 8.1 MPa, suggesting the dissolved CO2 in 3-nitrostyrene greatly promotes the dissolution of H2 in the substrate, which is responsible for the high catalytic activity at the peak of the inverted V-curve.