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The large‐scale use of fossil fuels had resulted in massive emission of CO2 and a series of serious environmental problems, which directly threatening human survival and sustainable development. CO2 is also the abundant carbon resource in C1 family. CO2 catalytic hydrogenation to CH4 is one of the effective ways to ultilize CO2 with low energy and high efficiency, which has been widely concerned in recent years. Suppoted nano‐Co/CeO2‐δ catalysts were prepared and evaluated their CO2 hydrogenation performances. XRD, H2‐TPR, H2‐TPD and CO2‐TPD had been conducted to study the physicochemical properties of the prepared Co/CeO2‐δ catalysts. The Co loading significantly affects the physicochemical properties and CO2 hydrogenation performances. The active metal Co species were highly diepersed on the CeO2 support surface. The number of active metal Co species, which formed by H2 reduction, increased with the increasing of Co loading. And the ability to adsorb and activate the reactant H2 and CO2 molecules was also enhanced, which effectively promoted the CO2 hydrogenation performances. Among of the studied Co/CeO2‐δ catalysts, the CoCe09 catalyst with Co loading of 9 % showed the best CO2 catalytic hydrogenation activity. In the reaction temperature of 240–400 °C, the CO2 conversion and CH4 selectivity follow the order: CoCe01

The adsorbed CO 2 molecules can be easily activated to CO 2 * species by accepting electrons, which subsequently react with the activated H* species to generate the formate or CO intermediate species. Then, the generated intermediate species can be deeply hydrogenated to produce CH 4. The Co0 species and oxygen vacancies on the xCo/MnO catalysts surface both act as the active centers to catalyze the CO 2 hydrogenation reaction. The Co loading can deeply affect the CO 2 hydrogenation reaction by affecting the concentration of oxygen vacancies, metal-support interaction and the basic site numbers on the prepared xCo/MnO catalysts, which are critical to the formation of active centers and the CO 2 adsorption ability of the xCo/MnO catalysts. [Display omitted] • xCo/MnO catalysts with high CO 2 hydrogenation performances can be prepared. • The Mn 1-y Co y O solid solution can be formed in the prepared xCo/MnO catalysts. • Co0 species are the main active centers for CO 2 hydrogenation. • The basic and hydrogenation active sites can be regulated by Co loading. CO 2 hydrogenation technology has great potential for mitigating the greenhouse effect and creating a green economy. The development of catalysts plays a key role in the progress of CO 2 hydrogenation technology. In this study, the xCo/MnO catalysts for CO 2 hydrogenation reaction were prepared by the impregnation method using MnO x as the catalyst support. And the effects of the Co loading on the CO 2 hydrogenation performances of the prepared xCo/MnO catalysts were investigated. The active Co0 species on the xCo/MnO catalysts surface are the main active centers for the CO 2 hydrogenation reaction, and the medium basic sites on the xCo/MnO catalysts are the main CO 2 adsorption sites. The MnO x support possesses a large number of medium basic sites, which can enhance the CO 2 molecules adsorption ability of the xCo/MnO catalysts. An effective regulation of the basic and hydrogenation active site numbers on the xCo/MnO catalysts surface can be achieved by changing the Co loading amount, which in turn can affect the CO 2 molecules adsorption, activation and hydrogenation abilities of the xCo/MnO catalysts. Moreover, the Mn 1-y Co y O solid solution was found to be formed in the prepared xCo/MnO catalysts, which is conducive to the dispersion of metal Co nanoparticles on the MnO surface and the generation of oxygen-deficient sites. The CO 2 desorption amount on the 12Co/MnO catalyst reached 1.76 mmol/g, which provided the catalyst with strong CO 2 adsorption and activation abilities, enabling it to exhibit great CO 2 hydrogenation performance. Under the conditions of atmosphere and 420 °C, the CO 2 conversion and CH 4 selectivity on the prepared 12Co/MnO catalyst reached 57.5 % and 78.8 %, separately. Furthermore, the CO 2 conversion was able to consistently remain at the initial 57.5 %, and the CH 4 selectivity was maintained above 70.0 % in the 10 times CO 2 hydrogenation cycle tests on the 12Co/MnO catalyst. Our study highlights the potential of using MnO x as catalyst support in the CO 2 hydrogenation reaction, and the findings will provide convenient for the future studies. [ABSTRACT FROM AUTHOR]

Metal-organic frameworks (MOFs) are emerging microporous materials that are promising for capture and sequestration of CO2 due to their tailorable binding properties. However, it remains a grand challenge to pre-design a MOF with a precise, multivalent binding environment at the molecular level to enhance CO2 capture. Here, we report the design, synthesis, and direct X-ray crystallographic observation of a porphyrinic MOF, UNLPF-2, that contains CO2-specific single molecular traps. Assembled from an octatopic porphyrin ligand with [Co2(COO)4] paddlewheel clusters, UNLPF-2 provides an appropriate distance between the coordinatively unsaturated metal centers, which serve as the ideal binding sites for in situ generated CO2. The coordination of CoII in the porphyrin macrocycle is crucial and responsible for the formation of the required topology to trap CO2. By repeatedly releasing and recapturing CO2, UNLPL-2 also exhibits recyclability. [ABSTRACT FROM AUTHOR]

The surface active centers, which include metal Co, surface oxygen vacancies, and Co0–CeO 2-δ interface structures, can be constructed on the mesoporous Co/CeO 2-δ catalysts by wet impregnation method. And the surface active centers can be regulated by the Co species dosage. The interaction between the metal Co and CeO 2-δ can promote surface oxygen vacancies and Co0–CeO 2-δ interface structures to be formed and be conducive to inhibit the aggregation and sintering of Co species in high temperature environment. The prepared Co/CeO 2-δ catalysts have better catalytic performances for CO 2 hydrogenation than the single component Co and CeO 2-δ catalysts, which can be attributed to the synergistic effect between Co0 active centers, surface oxygen vacancies, and Co0–CeO 2-δ interface structures. Therefore, the Co/CeO 2-δ catalysts have strong adsorption and activation ability for reactant CO 2 and H 2 molecules to improve the CO 2 hydrogenation activity. At atmospheric pressure and 400 °C, the CO 2 conversion and CH 4 selectivity on the Co/CeO 2-δ catalyst with Co loading of 12% could reach 59.7% and 95.7%, respectively, and maintained good stability in 9 cycles for CO 2 hydrogenation reaction. • Co0–CeO 2-δ interface structure can be constructed by impregnation method. • Interaction between Co and Ce species promote oxygen vacancy and Co0 to form. • Co0 and oxygen vacancy are mainly active centers in CO 2 hydrogenation. • There is synergy effect among Co0–CeO 2-δ , pore structure, oxygen vacancy, and Co0. [ABSTRACT FROM AUTHOR]

[Display omitted] • Porous CoCex catalyst can be prepared by hydrothermal assisted soft template method. • Co0 species are the active centers for CH 4 /CO 2 dry reforming. • Ce species can produce strong electronic effects with Co species. • Oxygen vacancies can promote the oxidative elimination of carbon deposition. The CoCex composite catalysts prepared by hydrothermal assisted template agent CTAB, have superior catalytic performances for CH 4 /CO 2 dry reforming (DRM). The physicochemical properties of the catalysts were investigated in depth with the help of XRD, H 2 -TPR, CO 2 -TPD, ICP, Quasi in-situ XPS and N 2 adsorption–desorption measurements. The transition metal Co is the main active center in the DRM reaction, which can easily release the outer electrons in the reaction to activate the reactant molecules. The introduction of Ce species can promote the highly dispersed metal Co species and catalytic active centers to be formed, as well as the adsorption and activation of CO 2 molecules by the catalyst. Ce species can produce strong electronic effects with Co species, which can promote the electron-deficient CeO 2-δ and electron-rich Coδ- species to be formed. The formation of CeO 2-δ species facilitates the adsorption and activation of CO 2 molecules, and the active oxygen species on the CeO 2-δ surface facilitates the oxidative activation for CH 4 molecules. The CH 4 and CO 2 reactant molecules can be adsorbed and activated by the formed Coδ- species to form CH 4-x (x = 0–4) and CO 2 δ- reactive species, which can promote the DRM reaction. The Co/Ce molar ratio has an important effect on the physicochemical properties and CO 2 adsorption performance of CoCex catalysts. And the CoCe2 catalyst prepared at a 2.0 Co/Ce molar ratio exhibited superior catalytic performance and high stability for the DRM reaction. The CH 4 and CO 2 conversion of the CoCe2 catalyst reached 88.6%, and 52.1% at 700 °C, respectively. In addition, the CoCe2 catalyst can maintain high cycle stability for CH 4 /CO 2 dry reforming. [ABSTRACT FROM AUTHOR]

[Display omitted] • Chlorine in MSWI fly ash is the main barrier to its recycling in cement kiln. • CO 2 injection during washing promoted decomposition of hardly soluble salts. • CO 2 -aided washing increased Cl removal rates by 6–9% than water washing. • CO 2 -aided washing could promote recycling of fly ash in cement kiln. Municipal solid waste incineration (MSWI) fly ash contains many harmful components that may limit its potential for recycling. An effective pretreatment is therefore required before any recycling can be implemented. In this study, the effects of four pretreatment methods (water washing, CO 2 -aided washing, CO 3 2–-aided washing, and CO 2 and CO 3 2–-aided washing) on the extraction behavior of chloride, sulfate, and heavy metals were evaluated. Water washing was found to be effective for the extraction of all easily and moderately soluble Cl-bearing salts, achieving Cl extraction ratios of 88%, 90%, and 96% for ash from Chongqing (CQ), Qingdao (QD), and Tianjin (TJ), respectively. Injection of CO 2 during washing facilitated decomposition of the hardly soluble Cl-bearing salts, increasing the Cl extraction efficiency by 6% for CQ ash and 9% for QD ash. However, for the TJ ash that contained few insoluble Cl-bearing minerals, CO 2 injection decreased the Cl extraction rate. The addition of CO 3 2– had a negative influence on Cl extraction for all ashes, but it slightly promoted sulfate extraction. Despite the high Cl removal rate, only 23–37% of the sulfate and 0.1–12% of heavy metals were removed. Overall, water-based pretreatment, especially CO 2 -aided washing, significantly altered the physical, chemical, and mineralogical characteristics of the fly ash, making it more suitable for recycling. Consequently, the blending ratio of the fly ash for cement clinker manufacture increased from 0.2 to 0.3% in the raw ash to 3.5–5.5% in the treated ash, enabling the extensive use of ash materials. [ABSTRACT FROM AUTHOR]

[Display omitted] • The crystal structure of the unique MOF (1) containing [Tb-F] n chains is reported here. • 1 is a low-cost MOF that can be efficiently obtained by precipitation way in H 2 O. • 1 is a smart luminescent sensor for high-toxic Cr(VI) in water. • 1 'can efficiently catalyze cycloaddition of CO 2 with epoxides to cyclic carbonates. The low cost, including material cost and energy cost, in large-scale production is an important metric for a metal–organic framework (MOF) towards real-world applications. This requires that the MOF can be efficiently synthesized in a high yield under mild enough conditions, while the employed organic ligands should be simple in structure and cheap. Motivated by such consideration, we established our work on a Tb-fluoride-oxalate framework [TbF(C 2 O 4)(H 2 O) 2 ] n ∙2nH 2 O (1), which meets the requirements stated above. The synthesis of its single-crystal sample and its crystal structure are first reported here. X-ray diffraction test shows 1 has a 3D microporous framework structure constructed by 1D [Tb-F] n chains and C 2 O 4 2− bridges. In fact, 1 is the unique complex that comprises [Tb-F] n chains. Though [Tb-F] n chain is of great interest in the field of molecular nanomagnets, direct-current and alternating-current magnetic susceptibilities reveal no slow magnetic relaxation behavior in 1. Luminescence investigation reveals that 1 exhibits strong green photoluminescence emission and can be used as a "turn-off" luminescent sensor for toxic Cr 2 O 7 2− and CrO 4 2− ions in aqueous solution with high selectivity and sensitivity. Besides, the strong Lewis acidity of Tb3+ also makes 1 a good heterogeneous catalyst for the cycloaddition reaction of CO 2 with epoxides to cyclic carbonates. [ABSTRACT FROM AUTHOR]