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This research is supported by the AMPM CCF fund (FCC/1/1972-43-01) to Y.H. from King Abdullah University of Science and Technology and the research grant to F.L. from the National Natural Science Foundation of China (No. 61971201).

For supported metal catalyst systems, the impact on catalysis originates from the interaction between metal nanoparticles and their support. Metal-support interactions (MSI) can change electronic properties, geometric morphologies, or chemical compositions of metal nanoparticles to make active sites have specific properties and catalytic activities. Fischer-Tropsch synthesis (FTS) is one of the most effective ways to convert cheap non-petroleum-based carbon sources into high value-added chemicals or ultra-clean liquid fuels. In this review, we summarize and classify the impact of MSI on the catalytic activity, selectivity and stability of FTS catalysts. The strategies to tune MSI are introduced in detail, and the recent development of high-efficiency FTS catalysts through the manipulation of SMI strategies has been highlighted. It is emphasized that the active metal sites, which are endowed with special functions by MSI, can change the strength of adsorption bond of adsorbates, consequently controlling the product distribution.

Sorption-based atmospheric water harvesting (SAWH), which uses sorbents to capture water vapor from the air and low-grade energy to produce fresh liquid water, has been recognized as a promising strategy for decentralized water supply in arid areas. This review aims to summarize the latest progress in this field and provide perspectives for the further development of SAWH, focusing on the design of sorbent materials and the optimization of the entire system. We first introduce the water sorption mechanisms on different sorbent materials. Next, we discuss the properties and performances of various sorbents developed for SAWH by categorizing them into specific groups: nanoporous solids, hygroscopic polymers, salt-based composites, and liquid sorbents; for each type of sorbent materials, we have analyzed its advantages and limitations, as well as design strategies. In addition, we discuss the influences of the mass and heat transport of the SAWH system on its overall performance in actual operations, and introduce different types of water harvesters developed for SAWH. In the last section, we outline the challenges in this field from fundamental research and practical application aspects, and describe roadmaps for the future development of this technology.

The selective oxidation of CH4 in the aqueous phase to produce valuable chemicals has attracted considerable research attention due to its mild reaction conditions and simple process. As the most widely studied catalyst for this reaction, Fe-containing ZSM-5 zeolite (Fe-ZSM-5) demonstrates high intrinsic activity and selectivity; however, Fe-ZSM-5 prepared using conventional methods has a limited number of active Fe sites, resulting in low CH4 conversion per unit mass of the catalyst. To address this issue, this study reports a facile organic-template-free synthesis strategy that enables the incorporation of more Fe into the zeolite framework with a higher dispersion degree compared to conventional synthesis methods. Because framework Fe incorporated in this way is more readily to transform into isolated extra-framework Fe species under thermal treatment, the overall effect is that Fe-ZSM-5 prepared using this method (Fe-HZ5-TF) has three times as many catalytically active sites as conventional Fe-ZSM-5. When used for the selective oxidation of CH4 (30.5 bar) with 0.5 M H2O2 at 75°C, Fe-HZ5-TF produced a record high C1 oxygenate yield of 106.3 mmol gcat−1 h− 1 (a HCOOH selectivity of 91.3%), surpassing other catalysts reported to date. Spectroscopic characterization and density functional theory calculations revealed that the active sites in Fe-HZ5-TF are mononuclear Fe species in the form of [(H2O)3Fe(IV) = O]2+ bound to Al pairs in the zeolite framework. This differs from conventional Fe-ZSM-5, where binuclear Fe acts as the active site. Analysis of the catalyst and product evolution during the reaction suggests a radical-driven pathway to explain CH4 activation at the mononuclear Fe site and subsequent conversion to C1 oxygenates.

Herein, we report the effect of the hot-water pretreatment on the catalytic activity of the H-mordenite (H-MOR) zeolite for DME carbonylation. The structure and acidity of the H-MOR catalysts pretreated by hot water were systematically characterized by XRD, nitrogen adsorption, SEM, H2O-TPD, NH3-TPD, 1H NMR and NH3-DRIFTS technologies. With the increase of the duration of the hot-water pretreatment, the catalytic activity shows a volcano-type variation. The H-MOR catalyst pretreated by hot water for 10 min at 573 K displays the highest catalytic activity among all of the catalysts. The appropriate duration of the hot-water pretreatment can generate new medium strong and strong Bronsted acid sites, which changes the microenvironment in the pores of H-MOR. Additionally, the newly generated Bronsted acid sites will accelerate the first step of DME carbonylation, that is, DME reacts with the Bronsted acid sites of the zeolite forming surface methoxy groups and methanol, improving the catalytic activity of the catalysts. However, too long duration of the hot-water pretreatment will remain water molecules in H-MOR, which inhibits DME carbonylation.

N-doped carbon supports are promising to improve reduction degree and dispersion of metal catalysts in Fischer-Tropsch synthesis (FTS). However, it is a great challenge to reasonably construct desired N dopants on FTS catalysts. Herein, we report the high FTS performance of the Co catalysts supported on N-doped carbon nanospheres synthesized by using a facile strategy. Through precisely tailoring the N dopants, we discover that the interaction between cobalt catalysts and supports is significantly strengthened via donation electron function of N atoms, especially for pyrrolic N. It improves the dispersion of cobalt species to generate more electron-enriched cobalt sites, which can strongly adsorb CO and accelerate CO dissociation to C*, resulting in the enhanced catalytic activity. In addition, these in turn increase C* concentration on the surface of the active cobalt sites, which is favorable to form a high concentration of chain initiators CH2 to stimulate carbon-chain growth, inducing the high selectivity towards the C5+ products in FTS. Accordingly, the Co/NCS-500 catalyst with the high content of pyrrolic N presents the high FTS activity and C5+ selectivity. Our work provides a new avenue in rational development of other related heterogeneous catalysis.

Zeolite catalysts, such as H-mordenite (H-MOR), are readily deactivated by coke deposition in carbonylation reactions. Pyridine modification of H-MOR can improve its stability but can lead to an undesirable loss in catalytic activity. Herein, we report the intrinsic impact of the pyridine adsorption behavior on H-MOR and the spacial hindrance of the zeolite frameworks on dimethyl ether (DME) carbonylation at a molecular level. We discovered that acid sites at O2 positions, located on common walls of eight-membered ring (8-MR) side pockets and 12-MR channels, were active in DME carbonylation, but were unfortunately poisoned during pyridine modification. Density functional theory calculations revealed that the pyridine-poisoned acid sites at the O2 positions could be easily regenerated due to the spacial hindrance of the zeolite frameworks. Accordingly, they can be facilely regenerated by proper thermal treatment, which induces 60% promotion in the catalytic activity along with a high stability. Our findings demonstrate the determining role of O2 positions in H-MOR for DME carbonylation and provide a new avenue for the rational design of other efficient zeolite-relevant catalytic systems.

Herein, we investigate the De-NOx activity of Pt/Ba/SnxCe1–xO2 catalysts at high temperatures. Our results show that at high temperatures, their NOx storage capacity (NSC), linked to the quantity of highly dispersed BaCO3 species on the catalysts, determines the De-NOx activity instead of the NOx oxidation and reduction ability. Moreover, we identify that monodentate nitrate species are more stable than free ion nitrate species on the Ce-containing catalysts. Thus, the presence of monodentate nitrate species is beneficial to improve the H2O and CO2 tolerance by inhibiting the latter ones’ competitive adsorption on NOx storage sites. Compared with other catalysts, Pt/Ba/Sn0.8Ce0.2O2 possesses the larger amount of highly dispersed BaCO3 species, and especially, more monodentate nitrate species are formed on it during the NOx storage period. Thus, it exhibits the superior De-NOx performance with NOx removal percentage over 86% in the presence of H2O and CO2 at 350∼500 °C.

The production of 1-butene by ethylene dimerization is an important chemical industrial process currently implemented using homogeneous catalysts. Here, we describe a highly active heterogeneous catalyst (Ni-ZIF-8) for ethylene dimerization, which consists of isolating Ni-active sites selectively located on the crystal surface of a zeolitic imidazolate framework. Ni-ZIF-8 can be easily prepared by a simple one-pot synthesis method in which site-specific anchoring of Ni is achieved spontaneously because of the incompatibility between the d8 electronic configuration of Ni2+ and the three-dimensional framework of ZIF-8. The full exposure and square-planar coordination of the Ni sites accounts for the high catalytic activity of Ni-ZIF-8. It exhibits an average ethylene turnover frequency greater than 1 000 000 h-1 (1-butene selectivity >85%) at 35 °C and 50 bar, far exceeding the activities of previously reported heterogeneous catalysts and many homogeneous catalysts under similar conditions. Moreover, compared to molecular Ni complexes used as homogeneous catalysts for ethylene dimerization, Ni-ZIF-8 has significantly higher stability and shows constant activity during 4 h of continuous reaction. Isotopic labeling experiments indicate that ethylene dimerization over Ni-ZIF-8 follows the Cossee-Arlman mechanism, and detailed characterizations combined with density functional theory calculations rationalize this observed high activity.

ZE41A magnesium alloy was selected as matrix material, using hydrothermal method for the synthesis of the surface coating. The formation of anti-corrosion coatings on the surface of magnesium alloy was investigated in pure water. By adjusting the experimental parameters such as the hydrothermal time (1-3 h) and the hydrothermal temperature (120-160 °C), the generation of the coating on the magnesium alloy surface is regulated. The surface morphologies, composition phase, and corrosion resistance of the hydrothermal conversion coatings were investigated by the method of scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) and electrochemical corrosion tests. Results show that prolonged hydrothermal time and increased hydrothermal temperature change the morphologies as well as the chemical compositions of formed coatings from a relative loose structure with few magnesium hydroxides into a fine dense one with higher amount of magnesium hydroxide.

Herein, we prepared a series of H-Zn-mordenite (H-Zn-MOR) catalysts by adding zinc source into the initial sols during the synthesis of mordenite (MOR). The results indicated that isolated Zn ions were highly dispersed in the catalysts. The addition of zinc led to the increase of Si/Al in the framework of MOR, the change of the distribution of acid sites and the change of acid strength. We investigated the catalytic performance of the H-Zn-MOR catalysts and the HMOR catalysts for carbonylation of dimethyl ether to methyl acetate. The addition of zinc improved the catalytic performance and made the drop of the conversion over the Zn-0.003 and Zn-0.005 catalysts to be about the half of that over the HMOR catalyst. We attributed it to the change of the acid properties, which further change the rate of coke deposition.

This paper describes how Cu+ species act as electrophilic sites to facilitate the adsorption and activation of formate and restrict the Ostwald ripening of Cu species, leading to an efficient and robust steam reforming of bio-DME., Catalytic reforming provides a practical technique for on-board hydrogen production in fuel cell applications. The high energy density, easy transportation and non-toxicity of biomass-derived dimethyl ether (bio-DME) offer potential to replace methanol for on-board steam reforming (SR). Presently, the reaction mechanism over conventional Cu-based SR catalysts remains elusive, limiting the rational design of highly efficient reforming systems. Herein, we build a catalytic system for bio-DME SR with dual-sites of Cu species, i.e., Cu+ and Cu0 sites, and achieve a record-high H2 production rate of 1145 mol kgcat–1 h–1. Via regulating the ratios of the dual-sites of Cu, we clearly describe molecular understandings on SR. And we discover that the substantially boosted activity is induced by a new Cu+-determined reaction path substituting the conventional Cu0-determined path. Intrinsically, Cu2O can act as a physical spacer and hydroxyl consumer to suppress the aggregation of metallic Cu species in SR. Due to the unique structure of metallic Cu surrounded by Cu2O, the catalyst exhibits robust catalytic performance even after severe thermal treatment. These findings open a new avenue for designing efficient catalytic reforming systems with commercial potential.

Ultrathin ceria nanosheets with exposed reactive {110} facets are synthesized to evaluate the influence of its unique nanostructure on the low-temperature redox behavior. Via a systematic comparison of the ceria nanosheets with nanorods and nanoparticles, we demonstrate that the nanosheets show the enhanced redox reaction activity and the reduced reduction temperature. Through in situ XAFS experiments, we disclose that the ultrathin nanosheets intrinsically decrease the coordination number of Ce atoms and increase the disorder of ceria face-centered cubic fluorite structure, ultimately enhance the oxygen reactivity as well as mobility. Remarkably, the nanosheets exhibit the temperature-independent reducibility between 150 and 250 °C. Through in situ DRIFTS experiments, we demonstrate that the unidentate carbonates are probably the most active surface carbonates species on the redox reaction. The bidentate carbonates are speculated to be the main carbonate species as CO molecules adsorb and diffuse on the ...

Herein, we synthesized CeO 2 nanocrystals (Ce250) with a large number of surface lattice defects by calcining the superfine Ce(OH) 3 nanowires at 250 °C. They were then utilized as the support of the CuO catalysts for CO preferential oxidation (CO PROX). The strong interaction between CuO and CeO 2 is the key factor to improve the catalytic activity, and our results show that the surface lattice defects on the CeO 2 support can strengthen the interaction between CuO and CeO 2 during the catalyst preparation procedure. With the increase of the calcination temperature, the surface areas of the CuO/CeO 2 catalysts gradually drops, but the interaction between CuO and CeO 2 is strengthened. Their catalytic activities present a “volcano” type, and the CuCe500 calcined at 500 °C shows the highest catalytic activity.

Herein, we report the high activity of CuO-SnO2 catalysts for the catalytic oxidation of CO. In particular, SnCu30 shows the highest activity and a high water resistance. If we compare the XRD, X-ray absorption fine structure, and H2 temperature-programmed reduction results of SnCu30 before and after HNO3 treatment, we find the existence of three kinds of Cu species in the catalyst, that is, highly dispersed CuO, bulk CuO, and Cu incorporated in the SnO2 lattice. The highly dispersed CuO and the surface lattice oxygen species are the active sites for the catalytic oxidation of CO. We used X-ray photoelectron spectroscopy and in situ diffuse reflectance infrared Fourier transform spectroscopy to confirm the existence of Cu+ species on the surface of the CuO-SnO2 catalysts, which can provide the adsorption sites for CO. Our results show that the reaction pathways of the catalytic oxidation of CO over the CuO-SnO2 catalysts follow the Mars–van Krevelen model.

Summary Molybdenum supported on zeolite HZSM-5 is the most studied catalyst for methane dehydroaromatization. However, the nature of its catalytic sites and their deactivation mechanisms remain unclear and controversial. Here, we report further insights into this system: first, the crystal size of HZSM-5 determines the form and location of the catalytic active MoCx species, and thus the catalyst performance; second, MoCx sites are preferentially deactivated over acid sites, when supported on nano-sized HZSM-5; third, MoCx particles that are traditionally considered detrimental to the reaction can serve as active sites, if they are properly protected from coke deposition. These findings lead us to develop an “encapsulation” strategy, which reconciles the deactivation rates of the MoCx and acid sites, enabling a full utilization of both sites, and consequently leading to a 10-fold increase in catalyst lifetime. Encapsulation also allows us to design experiments to confirm the catalytic role of the acid sites.

Generally, strong metal–support interactions of reducible metal oxides supports will cause encapsulation of suboxides on metal catalysts. It inevitably brings the formation of metal–support interfacial sites, and decreases surface-exposed metal sites. Herein, we synthesize Ru/TiO2 catalysts through a dopamine sacrificial coating strategy, which significantly increases the number of surface-exposed Ru sites with the high dispersion. The as-synthesized Ru/TiO2-500-H catalyst exhibits the high Fischer–Tropsch synthesis performance and catalytic stability. We discover that the TOF of surface-exposed Ru sites is 5.3-fold that of interfacial ones in our catalyst system. Moreover, surface-exposed Ru sites could thermal-stably adsorb CO, stimulate the chain growth and promote the C5+ selectivity by strengthening the bond between CHx intermediates and metal sites, as evidenced by in situ characterizations operated under real operating conditions. Our findings provide comprehensive understandings of rationally designing highly efficient metal catalysts, which can be potentially applied in other related catalysis systems.

Hard coke blockage of micropores of acidic zeolites generally causes serious catalytic deactivation for many chemical processes. Herein, we report a facile method to synthesize H-mordenite nanosheet assemblies without using any template agent. The assemblies exhibit the high catalytic activity for carbonylation of dimethyl ether because of their large quantity of framework Bronsted acids. The specific morphology of the nanosheet unites improves mass diffusion for both reactants and products. Consequently, the coke precursor species can readily migrate from the micropores to the external surface of the assemblies, inducing the improved catalytic stability through inhibiting hard coke formation in frameworks.