The interface of metal-oxide plays pivotal roles in catalytic reactions, but its catalytic function is still not clear. In this study, we report the high activity of nanostructured Ru/ceria (Ru-clusters/ceria) in the ethylene methoxycarbonylation (EMC) reaction in the absence of acid promoter. The catalyst offers 92% yield of MP with TOF of 8666 h, which is about 2.5 times of homogeneous Pd catalyst (∼3500 h). The interfacial Lewis acid-base pair [Ru-O-Ce-Vö], which consists of acidic Ce-Vö (oxygen vacancy) site and basic interfacial oxygen of Ru-O-Ce linkage, acts as active site for the dissociation of methanol and the subsequent transfer of hydrogen to the activated ethylene, which is the key step in acid-promoter-free EMC reaction. The combination of H MAS NMR, pyridine-IR and DFT calculations reveals the hydrogen species derived from methanol contains Brönsted acidity. The EMC reaction mechanism under acid-promoter-free condition over Ru-clusters/ceria catalyst is discussed.

In the past two decades, on account of the energy and environmental crisis brought by the decline in fossil resources, price volatility, and climate change, the high-value utilization of biomass feedstocks has gradually attracted widespread attention. Catalytic conversion of biomass usually involves tandem activation and cleavage of C–C and C–O bonds. Some steps occur in the aqueous phase and demand catalysts of high water resistance. Water-resistant ceria with redox and acid–base synergistic catalytic sites has attracted great interests particularly for biomass upgradation. The reversible Ce3+/Ce4+ redox pairs and the existence of oxygen vacancies improve its redox ability and thus catalytic activity. Besides, the acid–base properties enable its use in acid–base catalytic reactions. The strength or concentration of acid–base sites is tailorable. The water-tolerance character is unique and thus can be employed in the conversion of dilute aqueous biomass solutions. In this Perspective, we summarize the latest research progress in the high-value utilization of biomass feedstocks, including biomass raw materials, platform molecules originated from biomass as well as its derivatives and downstream chemicals over pure CeO2, doped CeO2, and CeO2-supported metal catalysts.

Selective conversion of an aqueous solution of mixed oxygenates produced by biomass fermentation to a value-added single product is pivotal for commercially viable biomass utilization. However, the efficiency and selectivity of the transformation remains a great challenge. Herein, we present a strategy capable of transforming ~70% of carbon in an aqueous fermentation mixture (ABE: acetone–butanol–ethanol–water) to 4-heptanone (4-HPO), catalyzed by tin-doped ceria (Sn-ceria), with a selectivity as high as 86%. Water (up to 27 wt%), detrimental to the reported catalysts for ABE conversion, was beneficial for producing 4-HPO, highlighting the feasibility of the current reaction system. In a 300 h continuous reaction over 2 wt% Sn-ceria catalyst, the average 4-HPO selectivity is maintained at 85% with 50% conversion and > 90% carbon balance. This strategy offers a route for highly efficient organic-carbon utilization, which can potentially integrate biological and chemical catalysis platforms for the robust and highly selective production of value-added chemicals.

Quinazolinones, an important class of heterocyclic compounds, have been widely used in pharmaceuticals because of their biological activity. However, the efficient and economical synthesis of quinazolinones has remained a challenge. A novel synthetic approach has now been developed to produce quinazolinones from olefins, CO, and amines over heterogeneous Ru-clusters/ceria catalyst in the absence of acids, bases, and oxidants. Furthermore, H O is generated as the only by-product. A series of quinazolinones with aromatic or non-aromatic substituents can be obtained in yields of up to 99 %. The Ru-clusters/ceria can be reused at least four times. The analysis of the E-factor (environmental impact factor) for the synthesis of 2-ethyl quinazolinone suggests that this system is more environmentally friendly than other processes reported previously.

Uncovering the underlying kinetics mechanism of the charge carrier during the transfer process is of fundamental importance in pursuing outstanding photocatalytic activity. However, it still remains a challenge owing to the rapid reaction rate of the charge carrier on the surface of photocatalysts. Here, in situ single-molecule fluorescence microscopy is employed to study the photoelectron-transfer kinetics in real time for an individual TiO2-tipped carbon nanotube (TiO2-tipped CNT) using a redox-responsive fluorogenic probe. A visual transport process for electron transfer from TiO2 nanoparticles to CNT is obviously observed via single-molecule fluorescence imaging. Based on the fluorescent product formation rate, the kinetics information of the photoelectron-transfer process can be obtained. The kinetics analysis results show that heterogeneity of catalytic activity caused by the photoelectron reactive sites exists in an individual TiO2-tipped CNT heterostructure, which is always masked in the ensemble measurement. After applying an adaptive high-resolution algorithm, which considers temporal and spatial factors into consideration simultaneously, the dynamic heterogeneity of special location on CNT within the TiO2-tipped CNT heterostructure in product formation is revealed with 40 nm spatial resolution. Moreover, we prove that the photoelectron-transfer distance on CNT can be up to 16.82 μm. These results give a deep insight into the kinetics information of the photoelectron-transfer process and a policy toward designing better photocatalysts.

Capping with pyridine, benzoic acid, and DMSO in catalytic reactions reveals the locations of surface active sites of CeO2.

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We constructed a single-molecule fluorescence imaging technique to monitor the spatiotemporal distribution of the hydroxyl radical (•OH) on TiO2-attached multiwalled carbon nanotubes (TiO2-MWCNTs) in aqueous. We found the heterogeneous distribution of •OH is closely related to the composition and heterostructure of the catalysts. The dynamic •OH production rate was evaluated by counting the single-molecule fluorescent bursts. We further confirmed the production of •OH on TiO2-MWCNTs mainly occurred via electron reduction during the aqueous photocatalytic process. Our study reveals the mechanism of reactive oxygen species involved photocatalytic reaction and guides the design of advanced semiconductor photocatalysts.