List of Issues

Chinese Journal of Catalysis
2021, Vol. 42, No. 7
Online: 18 July 2021

Previous Issue    Next Issue

Cover: Chen and co-workers reported a composition-graded oxygen reduction electrocatalyst of PtCu₃@Pt₃Cu@Pt nanodendrites possessing rich spiny branches exposing n(111)×(110) high index surfaces (HISs), formed through atmospheres-modulated morphology control of nanocrystals followed by electrochemical dealloying. Experimental characterizations and DFT calculations reveal that Cu alloying and HISs synergistically produce excellent oxygen reduction activity. Read more about the article behind the cover on pages 1108–1116.

For Selected:

Download Citations EndNote Ris BibTeX

Toggle Thumbnails

Highlight

Select

Photocatalytic antibacterial and osteoinductivity S. Wageh, Ahmed A. Al-Ghamdi, Lijun Liu 2021, 42 (7):  1051-1053.  DOI: 10.1016/S1872-2067(20)63742-1 Abstract ( 177 )   HTML ( 246 )   PDF (1125KB) ( 205 )

Reviews

Select

Iridium-containing water-oxidation catalysts in acidic electrolyte Yipu Liu, Xiao Liang, Hui Chen, Ruiqin Gao, Lei Shi, Lan Yang, Xiaoxin Zou 2021, 42 (7):  1054-1077.  DOI: 10.1016/S1872-2067(20)63722-6 Abstract ( 609 )   HTML ( 39 )   PDF (5339KB) ( 869 )   With the goal of constructing a carbon-free energy cycle, proton-exchange membrane (PEM) water electrolysis is a promising technology that can be integrated effectively with renewable energy resources to produce high-purity hydrogen. IrO2, as a commercial electrocatalyst for the anode side of a PEM water electrolyzer, can both overcome the high corrosion conditions and exhibit efficient catalytic performance. However, the high consumption of Ir species cannot meet the sustainable development and economic requirements of this technology. Accordingly, it is necessary to understand the OER catalytic mechanisms for Ir species, further designing new types of low-iridium catalysts with high activity and stability to replace IrO2. In this review, we first summarize the related catalytic mechanisms of the acidic oxygen evolution reaction (OER), and then provide general methods for measuring the catalytic performance of materials. Second, we present the structural evolution results of crystalline IrO2 and amorphous IrOx using in situ characterization techniques under catalytic conditions to understand the common catalytic characteristics of the materials and the possible factors affecting the structural evolution characteristics. Furthermore, we focus on three types of common low-iridium catalysts, including heteroatom-doped IrO2 (IrOx)-based catalysts, perovskite-type iridium-based catalysts, and pyrochlore-type iridium-based catalysts, and try to correlate the structural features with the intrinsic catalytic performance of materials. Finally, at the end of the review, we present the unresolved problems and challenges in this field in an attempt to develop effective strategies to further balance the catalytic activity and stability of materials under acidic OER catalytic conditions.

Select

Recent advances in VOCs and CO removal via photothermal synergistic catalysis Longfu Wei, Changlin Yu, Kai Yang, Qizhe Fan, Hongbing Ji 2021, 42 (7):  1078-1095.  DOI: 10.1016/S1872-2067(20)63721-4 Abstract ( 204 )   HTML ( 18 )   PDF (5049KB) ( 538 )   Currently, air pollution is being exacerbated by rapid social, economic, and industrial development. Major air pollutants include volatile organic compounds (VOCs) and CO. Photocatalytic and thermocatalytic technology can be used to convert VOCs and CO into harmless gases effectively. Recently, photothermal synergistic catalysis has aroused much attention because of its higher performance than those of individual photocatalytic and thermocatalytic processes. There have been many reviews on separate photocatalysts and thermocatalysts for the treatment of VOCs and CO, but few reviews have focused on photothermal synergistic catalysis. In this minireview, we concentrate on recent progress into photothermal synergistic catalysis for the efficient removal of VOCs and CO. The treatment of typical VOCs (such as benzene, toluene, ethanol, formaldehyde, acetone, propylene, and propane) and CO are summarized and analyzed. Furthermore, we discuss the use of conventional reactor technology, such as fixed-bed quartz reactors, for VOCs and CO removal. We also discuss the mechanism of the photothermal synergistic catalytic removal of VOCs and CO. Finally, we present perspectives for the photothermal synergistic catalytic removal of VOCs and CO.

Communications

Select

In situ evolution of surface Co2CrO4 to CoOOH/CrOOH by electrochemical method: Toward boosting electrocatalytic water oxidation Jinxiu Zhao, Xiang Ren, Xu Sun, Yong Zhang, Qin Wei, Xuejing Liu, Dan Wu 2021, 42 (7):  1096-1101.  DOI: 10.1016/S1872-2067(20)63730-5 Abstract ( 147 )   HTML ( 9 )   PDF (1543KB) ( 234 )   Supporting Information Developing non-noble-metal electrocatalyst with efficient and durable activity is a urgent task for addressing the sluggish reaction kinetics of electrochemical water oxidation. Structural evolution of the electrocatalyst is an important strategy for achieving enhanced performance. Herein, in situ evolution of surface Co2CrO4 to CoOOH/CrOOH (CoOOH/CrOOH-Co2CrO4) by an electrochemical method under alkaline conditions was designed for enhancing the electrocatalytic performance of water oxidation. The experiments demonstrated that the synergy between CoOOH/CrOOH and Co2CrO4 resulted in a marked increase in the number of active sites and improved the rate of charge transfer, which enhanced the activity for water oxidation. At a geometrical current density of 20 mA cm-2, the overpotential of the oxygen evolution reaction was 244 mV and the turnover frequency was 0.536 s-1 in 1.0 M NaOH.

Select

The catalytic properties of DNA G-quadruplexes rely on their structural integrity Jielin Chen, Mingpan Cheng, Jiawei Wang, Dehui Qiu, David Monchaud, Jean-Louis Mergny, Huangxian Ju, Jun Zhou 2021, 42 (7):  1102-1107.  DOI: 10.1016/S1872-2067(20)63744-5 Abstract ( 226 )   HTML ( 16 )   PDF (3923KB) ( 269 )   Supporting Information The influence of the G-quartet structural integrity on the catalytic activity of the G-quadruplex (G4) was investigated by comparing the G4-DNAzyme performances of a series of G4s with a G-vacancy site and a G-triplex (G-tri). The results presented herein not only confirm that the structural integrity of the 3'-end G-quartet is necessary for G4s to be catalytically competent but also show how to remediate G-vacancy-mediated catalytic activity losses via the addition of guanine surrogates in an approach referred to as G-vacancy complementation strategy that is applicable to parallel G4s only. Furthermore, this study demonstrates that the terminal G-quartet could act as a proximal coordinating group and cooperate with the flanking nucleotide to activate the hemin cofactor.

Articles

Select

High index surface-exposed and composition-graded PtCu3@Pt3Cu@Pt nanodendrites for high-performance oxygen reduction Yuxiang Liao, Jun Li, Shiming Zhang, Shengli Chen 2021, 42 (7):  1108-1116.  DOI: 10.1016/S1872-2067(20)63735-4 Abstract ( 189 )   HTML ( 17 )   PDF (1327KB) ( 273 )   Supporting Information Alloying and nanostructuring are two strategies used to facilitate the efficient electrocatalysis of the oxygen reduction reaction (ORR) by Pt, where the high index surfaces (HISs) of Pt exhibit superior activity for ORR. Here, we report the fabrication of PtCu3 nanodendrites possessing rich spiny branches exposing n(111) × (110) HISs. The dendrites were formed through an etching-modulated seeding and growing strategy. Specifically, an oxidative atmosphere was initially applied to form the concaved nanocubes of the Pt-Cu seeds, which was then switched to an inert atmosphere to promote an explosive growth of dendrites. Separately, the oxidative or inert atmosphere failed to produce this hyperbranched structure. Electrochemical dealloying of the PtCu3 nanodendrites produced Pt3Cu shells with Pt-rich surfaces where HIS-exposed dendrite structures were maintained. The resulting PtCu3@Pt3Cu@Pt nanodendrites in 0.1 M HClO4 exhibited excellent mass and area specific activities for ORR, which were 14 and 24 times higher than that of commercial Pt/C, respectively. DFT calculations revealed that Cu alloying and HISs both contributed to the significantly enhanced activity of Pt, and that the oxygen binding energy on the step sites of HISs on the PtCu3@Pt3Cu@Pt nanodendrites approached the optimal value to achieve a near peak-top ORR activity.

Select

Surface coupling of methyl radicals for efficient low-temperature oxidative coupling of methane Shihui Zou, Zhinian Li, Qiuyue Zhou, Yang Pan, Wentao Yuan, Lei He, Shenliang Wang, Wu Wen, Juanjuan Liu, Yong Wang, Yonghua Du, Jiuzhong Yang, Liping Xiao, Hisayoshi Kobayashi, Jie Fan 2021, 42 (7):  1117-1125.  DOI: 10.1016/S1872-2067(20)63756-1 Abstract ( 286 )   HTML ( 18 )   PDF (2115KB) ( 467 )   Supporting Information Selective coupling of methyl radicals to produce C2 species (C2H4 and C2H6) is a key challenge for oxidative coupling of methane (OCM). In traditional OCM reaction systems, homogeneous transformation of methyl radicals in O2-containing gases are uncontrollable, resulting in limited C2 selectivity and yield. Herein, we demonstrate that methyl radicals generated by La2O3 at low reaction temperature can selectively couple on the surface of 5 wt% Na2WO4/SiO2. The controllable surface coupling against overoxidation barely changes the activity of La2O3 but boosts the C2 selectivity by three times and achieves a C2 yield as high as 10.9% at bed temperature of only 570 °C. Structure-property studies suggest that Na2WO4 nanoclusters are the active sites for methyl radical coupling. The strong CH3· affinity of these sites can even endow some methane combustion catalysts with OCM activity. The findings of the surface coupling of methyl radicals open a new direction to develop OCM catalyst. The bifunctional OCM catalyst system, which composes of a methane activation center and a CH3· coupling center, may deliver promising OCM performance at reaction temperatures below the ignition temperature of C2H6 and C2H4 (~600 °C) and is therefore more controllable, safer, and certainly more attractive as an actual process.

Select

Catalytic roles of the acid sites in different pore channels of H-ZSM-5 zeolite for methanol-to-olefins conversion Sen Wang, Zhikai Li, Zhangfeng Qin, Mei Dong, Junfen Li, Weibin Fan, Jianguo Wang 2021, 42 (7):  1126-1136.  DOI: 10.1016/S1872-2067(20)63732-9 Abstract ( 313 )   HTML ( 18 )   PDF (1852KB) ( 387 )   Supporting Information H-ZSM-5 zeolite is a typical catalyst for methanol-to-olefins (MTO) conversion. Although the performance of zeolite catalysts for MTO conversion is related to the actual location of acid sites in the zeolite framework, the catalytic roles of the acid sites in different pore channels of the H-ZSM-5 zeolite are not well understood. In this study, the MTO reaction network, involving the aromatic cycle, alkene cycle, and aromatization process, and also the diffusion behavior of methanol feedstock and olefin and aromatic products at different acid sites in the straight channel, sinusoidal channel, and intersection cavity of H-ZSM-5 zeolite was comparatively investigated using density functional theory calculations and molecular dynamic simulations. The results indicated that the aromatic cycle and aromatization process occurred preferentially at the acid sites in the intersection cavities with a much lower energy barrier than that at the acid sites in the straight and sinusoidal channels. In contrast, the formation of polymethylbenzenes was significantly suppressed at the acid sites in the sinusoidal and straight channels, whereas the alkene cycle can occur at all three types of acid sites with similar energy barriers and probabilities. Consequently, the catalytic performance of H-ZSM-5 zeolite for MTO conversion, including activity and product selectivity, can be regulated properly through the purposive alteration of the acid site distribution, viz., the location of Al in the zeolite framework. This study helps to elucidate the relation between the catalytic performance of different acid sites in the H-ZSM-5 zeolite framework for MTO conversion, which should greatly benefit the design of efficient catalyst for methanol conversion.

Select

Ultrathin Ni(OH)2 nanosheets decorated with Zn0.5Cd0.5S nanoparticles as 2D/0D heterojunctions for highly enhanced visible light-driven photocatalytic hydrogen evolution Xueyou Gao, Deqian Zeng, Jingren Yang, Wee-Jun Ong, Toyohisa Fujita, Xianglong He, Jieqian Liu, Yuezhou Wei 2021, 42 (7):  1137-1146.  DOI: 10.1016/S1872-2067(20)63728-7 Abstract ( 118 )   HTML ( 12 )   PDF (1834KB) ( 396 )   Supporting Information Designing and fabricating highly efficient photocatalysts for water splitting is a promising strategy to address energy and environmental issues. Cadmium sulfide (CdS) has received significant interest as a photocatalyst for visible-light-induced hydrogen (H2) generation. However, the severe photocorrosion, high overpotential, rapid charge recombination, and sluggish surface reaction kinetics drastically hinder its practical application in water splitting. Herein, uniform zinc cadmium sulfide (Zn0.5Cd0.5S) nanoparticles were anchored on ultrathin Ni(OH)2 nanosheets via a facile solution-phase approach to form an intimate two-dimensional (2D)/zero-dimensional (0D) heterojunction. Under visible light irradiation, the 7%Ni(OH)2/Zn0.5Cd0.5S composite exhibited the highest H2 production rate of 6.87 mmol·h-1·g-1 with an apparent quantum yield of 16.8% at 420 nm, which is almost 43 times higher than that of pristine Zn0.5Cd0.5S and considerably higher than that of the Pt/Zn0.5Cd0.5S photocatalyst. The high photoactivity of the 2D/0D Ni(OH)2/Zn0.5Cd0.5S heterojunction can be ascribed to its unique and robust structure, wherein the ultrathin Ni(OH)2 nanosheets not only provide an excellent platform for the incorporation of Zn0.5Cd0.5S nanoparticles but also serve as an effective cocatalyst to promote photoinduced electron transfer and offer more active sites for photocatalytic H2 generation. This work paves the way toward the development of versatile, low-cost, and highly efficient 2D/0D heterojunction photocatalysts for solar energy conversion.

Select

Selective conversion of methanol to propylene over highly dealuminated mordenite: Al location and crystal morphology effects Li Ren, Bowen Wang, Kun Lu, Rusi Peng, Yejun Guan, Jin-gang Jiang, Hao Xu, Peng Wu 2021, 42 (7):  1147-1159.  DOI: 10.1016/S1872-2067(20)63726-3 Abstract ( 130 )   HTML ( 13 )   PDF (1434KB) ( 252 )   Supporting Information The growing consumption of light olefins has stimulated intensive researches on methanol to olefin (MTO) process which possesses great advantages for coal conversion to value-added chemicals in an environmentally benign way. The catalysts commonly used for MTO process faces several challenges such as poor selectivity control, low hydrothermal stability and short lifetime. In the present study, we prepared a series of mordenite zeolites with variable Al contents (Si/Al molar ratios of 51-436) by a sequential dealumination treatment of air-calcination and acid leaching. The textural properties, acidity and Al location before and after the dealumination treatment have been systematically studied and their effect on MTO especially the methanol to propylene (MTP) performance was thoroughly investigated. The mordenite zeolites with the Si/Al ratios over 150 selectively catalyzed methanol conversion in the MTP pathway, providing a high propylene selectivity of 63% and propylene/ethylene ratio of > 10. Compared to the low-silica MOR catalysts, highly dealuminated MOR showed much higher stability and longer lifetime, which can be further enhanced via harsh hydrothermal pretreatment. Furthermore, the lifetime was highly related to the crystal size along c-axis. The excellent performance of highly dealuminated MOR is likely ascribed to the mesopores formed upon dealumination and the scarce Al sites located in the T sites shared by the 8-member ring (MR) side pockets and 12-MR pore channels.

Select

Transition-metal-atom-pairs deposited on g-CN monolayer for nitrogen reduction reaction: Density functional theory calculations Bin Huang, Yifan Wu, Bibo Chen, Yong Qian, Naigen Zhou, Neng Li 2021, 42 (7):  1160-1167.  DOI: 10.1016/S1872-2067(20)63745-7 Abstract ( 128 )   HTML ( 9 )   PDF (2284KB) ( 295 )   Supporting Information The development of highly active DFT catalysts for an electrocatalytic N2 reduction reaction (NRR) under mild conditions is a difficult challenge. In this study, a series of atom-pair catalysts (APCs) for an NRR were fabricated using transition-metal (TM) atoms (TM = Sc-Zn) doped into g-CN monolayers. The electrochemical mechanism of APCs for an NRR has been reported by well-defined density functional theory calculations. The calculated limiting potentials were -0.47 and -0.78 V for the Fe2@CN and Co2@CN catalysts, respectively. Owing to its high suppression of hydrogen evolution reactions, Co2@CN is a superior electrocatalytic material for a N2 fixation. Stable Fe2@CN may be a strongly attractive material for an NRR with a relatively low overpotential after an improvement in the selectivity. The two-way charge transfer affirmed the donation-acceptance procedure between N2 and Fe2@CN or Co2@CN, which play a crucial role in the activation of inert N≡N bonds. This study provides an in-depth investigation into atom-pair catalysts and will open up new avenues for highly efficient g-CN-based nanostructures for an NRR.

Select

Donor-acceptor carbon nitride with electron-withdrawing chlorine group to promote exciton dissociation Jing-Wen Zhang, Lun Pan, Xiangwen Zhang, Chengxiang Shi, Ji-Jun Zou 2021, 42 (7):  1168-1175.  DOI: 10.1016/S1872-2067(20)63733-0 Abstract ( 119 )   HTML ( 3 )   PDF (3184KB) ( 224 )   Supporting Information Carbon nitride (C3N4) is promising for photocatalytic hydrogen production, but photogenerated electrons and holes in C3N4 usually tend to exist as excitons due to intrinsic Coulomb interactions making its photocatalytic activity unsatisfactory. Herein, a well-designed intramolecular C3N4-based donor-acceptor (D-A) photocatalytic system was constructed to promote exciton dissociation. Due to its good chemical compatibility with melamine and appropriate sublimation property, 2-amino-4,6-dichloropyrimidine unit was chosen as the monomer to react with melamine to construct intramolecular D-A system (CNClx). The hydrogen evolution rate of CNCl0.15 is 15.3 times higher than that of bulk C3N4 under visible light irradiation, with apparent quantum efficiency of 13.6% at 420 nm. The enhanced activity is attributed to introduced electron-withdrawing -Cl group as terminal group in the resulted CNClx samples, which can build internal electric field to promote the exciton dissociation into free electron and hole. In addition, lower work function value of CNClx samples indicates that internal electric field can help free electrons and holes transfer to the surface of CNClx samples for photocatalytic reaction.

Select

Tandem Lewis acid catalysis for the conversion of alkenes to 1,2-diols in the confined space of bifunctional TiSn-Beta zeolite Qifeng Lei, Chang Wang, Weili Dai, Guangjun Wu, Naijia Guan, Michael Hunger, Landong Li 2021, 42 (7):  1176-1184.  DOI: 10.1016/S1872-2067(20)63734-2 Abstract ( 154 )   HTML ( 4 )   PDF (2634KB) ( 295 )   Supporting Information The generation of multifunctional isolated active sites in zeolite supports is an attractive method for integrating multistep sequential reactions into a single-pass tandem catalytic reaction. In this study, bifunctional TiSn-Beta zeolite was prepared by a simple and scalable post-synthesis approach, and it was utilized as an efficient heterogeneous catalyst for the tandem conversion of alkenes to 1,2-diols. The isolated Ti and Sn Lewis acid sites within the TiSn-Beta zeolite can efficiently integrate alkene epoxidation and epoxide hydration in tandem in a zeolite microreactor to achieve one-step conversion of alkenes to 1,2-diols with a high selectivity of >90%. Zeolite confinement effects result in high tandem rates of alkene epoxidation and epoxide hydration as well as high selectivity toward the desired product. Further, the novel method demonstrated herein can be employed to other tandem catalytic reactions for sustainable chemical production.

Select

Geometric and electronic effects on the performance of a bifunctional Ru2P catalyst in the hydrogenation and acceptorless dehydrogenation of N-heteroarenes Fangjun Shao, Zihao Yao, Yijing Gao, Qiang Zhou, Zhikang Bao, Guilin Zhuang, Xing Zhong, Chuan Wu, Zhongzhe Wei, Jianguo Wang 2021, 42 (7):  1185-1194.  DOI: 10.1016/S1872-2067(20)63747-0 Abstract ( 130 )   HTML ( 4 )   PDF (1839KB) ( 176 )   Supporting Information The development of bifunctional catalysts for the efficient hydrogenation and acceptorless dehydrogenation of N-heterocycles is a challenge. In this study, Ru2P/AC effectively promoted reversible transformations between unsaturated and saturated N-heterocycles affording yields of 98% and 99%, respectively. Moreover, a remarkable enhancement in the reusability of Ru2P/AC was observed compared with other Ru-based catalysts. According to density functional theory calculations, the superior performance of Ru2P/AC was ascribed to specific synergistic factors, namely geometric and electronic effects induced by P. P greatly reduced the large Ru-Ru ensembles and finely modified the electronic structures, leading to a low reaction barrier and high desorption ability of the catalyst, further boosting the hydrogenation and acceptorless dehydrogenation processes.

Select

Zn-doping mediated formation of oxygen vacancies in SnO2 with unique electronic structure for efficient and stable photocatalytic toluene degradation Huizhong Wu, Jiadong Wang, Ruimin Chen, Chaowei Yuan, Jin Zhang, Yuxin Zhang, Jianping Sheng, Fan Dong 2021, 42 (7):  1195-1204.  DOI: 10.1016/S1872-2067(20)63737-8 Abstract ( 181 )   HTML ( 7 )   PDF (5585KB) ( 293 )   Supporting Information To optimize the electronic structure of photocatalyst, a facile one-step approach is developed for the simultaneous realization of Zn-doping and surface oxygen vacancies (SOVs) formation on SnO2. The Zn-doped SnO2 with abundant SOVs exhibits efficient and stable performance for photocatalytic degradation of toluene under both low and high relative humidity. Experimental and theoretical calculations results show that the synergistic effects of Zn-doping and SOVs on SnO2 can considerably boost the charge transfer and separation efficiency. Utilizing the in situ DRIFTS and theoretical calculations methods, it is revealed that the benzene ring of toluene is opened at benzoic acid on the SnO2 surface and selectively at benzaldehyde on the Zn-doped SnO2 surface. This implies that Zn-doped SnO2 photocatalysts shorten the pathway of toluene degradation, and toxic intermediates can be significantly inhibited. This work could provide a promising and sustainable route for safe and efficient removal of aromatic VOCs with photocatalytic technology.

Select

New strategy of S,N co-doping of conductive-copolymer-derived carbon nanotubes to effectively improve the dispersion of PtCu nanocrystals for boosting the electrocatalytic oxidation of methanol Jingping Zhong, Kexin Huang, Wentao Xu, Huaguo Tang, Muhammad Waqas, Youjun Fan, Ruixiang Wang, Wei Chen, Yixuan Wang 2021, 42 (7):  1205-1215.  DOI: 10.1016/S1872-2067(20)63748-2 Abstract ( 101 )   HTML ( 4 )   PDF (2428KB) ( 215 )   Supporting Information Efficacious regulation of the geometric and electronic structures of carbon nanomaterials via the introduction of defects and their synergy is essential to achieving good electrochemical performance. However, the guidelines for designing hybrid materials with advantageous structures and the fundamental understanding of their electrocatalytic mechanisms remain unclear. Herein, superfine Pt and PtCu nanoparticles supported by novel S,N-co-doped multi-walled CNT (MWCNTs) were prepared through the innovative pyrolysis of a poly(3,4-ethylenedioxythiophene)/polyaniline copolymer as a source of S and N. The uniform wrapping of the copolymer around the MWCNTs provides a high density of evenly distributed defects on the surface after the pyrolysis treatment, facilitating the uniform distribution of ultrafine Pt and PtCu nanoparticles. Remarkably, the Pt1Cu2/SN-MWCNTs show an obviously larger electroactive surface area and higher mass activity, stability, and CO poisoning resistance in methanol oxidation compared to Pt/SN-MWCNTs, Pt/S-MWCNTs, Pt/N-MWCNTs, and commercial Pt/C. Density functional theory studies confirm that the co-doping of S and N considerably deforms the CNTs and polarizes the adjacent C atoms. Consequently, both the adsorption of Pt1Cu2 onto the SN-MWCNTs and the subsequent adsorption of methanol are enhanced; in addition, the catalytic activity of Pt1Cu2/SN-MWCNTs for methanol oxidation is thermodynamically and kinetically more favorable than that of its CNT and N-CNT counterparts. This work provides a novel method to fabricate high-performance fuel cell electrocatalysts with highly dispersed and stable Pt-based nanoparticles on a carbon substrate.

Select

Enhancing the activity, selectivity, and recyclability of Rh/PPh3 system-catalyzed hydroformylation reactions through the development of a PPh3-derived quasi-porous organic cage as a ligand Wenlong Wang, Cunyao Li, Heng Zhang, Jiangwei Zhang, Lanlu Lu, Zheng Jiang, Lifeng Cui, Hongguang Liu, Li Yan, Yunjie Ding 2021, 42 (7):  1216-1226.  DOI: 10.1016/S1872-2067(20)63746-9 Abstract ( 130 )   HTML ( 8 )   PDF (1402KB) ( 361 )   Supporting Information In contrast to heterogeneous network frameworks (e.g., covalent organic frameworks and metal-organic frameworks) and porous organic polymers, porous organic cages (POCs) are soluble molecules in common organic solvents that provide significant potential for homogeneous catalysis. Herein, we report a triphenylphosphine-derived quasi-porous organic cage (denoted as POC-DICP) as an efficient organic molecular cage ligand for Rh/PPh3 system-catalyzed homogeneous hydroformylation reactions. POC-DICP not only displays enhanced hydroformylation selectivity (aldehyde selectivity as high as 97% and a linear-to-branch ratio as high as 1.89) but can also be recovered and reused via a simple precipitation method in homogeneous reaction systems. We speculate that the reason for the high activity and good selectivity is the favorable geometry (cone angle = 123.88°) and electronic effect (P site is relatively electron-deficient) of POC-DICP, which were also demonstrated by density functional theory calculations and X-ray absorption fine-structure characterization.

Select

Palladium-catalyzed enantioselective linear allylic alkylation of vinyl benzoxazinanones: An inner-sphere mechanism Kai Wang, Binli Wang, Xianghui Liu, Hongjun Fan, Yan Liu, Can Li 2021, 42 (7):  1227-1237.  DOI: 10.1016/S1872-2067(20)63751-2 Abstract ( 144 )   HTML ( 9 )   PDF (1362KB) ( 194 )   Supporting Information Palladium-catalyzed asymmetric allylic alkylation (AAA) of vinyl benzoxazinanones has become an important strategy for the synthesis of chiral nitrogen-containing heterocycle compounds. However, the asymmetric synthesis of linear-selective products has rarely been reported. The simultaneous control of regio-, E/Z- and enantioselectivities constitutes a major challenge and inhibits the advancement of this chemistry. Herein, we present a palladium-catalyzed AAA of vinyl benzoxazinanones with α-thiocyanato ketones, affording various chiral thiocyanates characterized with high linear-, E- and stereoselectivities. The reaction has a broad substrate scope and the chiral thiocyanates can be transformed to useful heterocycles. Experimental and computational studies suggest an inner-sphere mechanism for AAA process, which results from the acidic and coordination effect of the nucleophilic substrates with palladium catalyst.