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Photocatalytic CO2 reduction is a highly vital process for converting CO2 into valuable chemicals. However, the reaction always proceeds less efficaciously at low temperature. A combination of optical and thermal conditions is one of the feasible approaches to achieve the reaction with high efficiency and has gained much attention recently. In the present work, we prepared several Co–Cu–Mn trimetallic catalysts via a simple co-precipitation method, which were used in catalyzing photothermal CO2 reduction to hydrocarbons. The metal composition and reduction temperature of the catalysts had important effects on their structural and photoelectrical characteristics and adsorption behaviors, further resulting in diverse catalytic performances. Among the prepared trimetallic catalysts, Co7Cu1Mn1Ox(200), with a Co/Cu/Mn molar ratio of 7/1/1 and reduced at 200 °C in H2 for 2 h, could produce CH4 with an activity of 14.5 mmol gcat−1 h−1 in 10% CO2/30% H2/60% N2, and CH4 and C2+ hydrocarbons with the activities of 15.9 and 7.5 mmol gcat−1 h−1 in 25% CO2/75% H2, respectively. The present strategy for constructing trimetallic oxide catalysts for the photothermal reaction not only provides a highly active catalyst for CO2 utilization, but also offers a potential possibility for reducing the high temperature of conventional thermal reactions.

The rapid consumption of conventional fossil fuels has caused a sharp decline in their reserves and led to climate change. Exploitation of renewable energy sources especially bio-fuels such as 2,5-dimethylfuran (DMF), methylfuran (MF), γ-valerolactone (GVL), etc. has both environmental and economic benefits. In the present work, diverse Co-based bimetallic catalysts were prepared and used for catalyzing hydrodeoxygenation (HDO) of biomass-derived oxygenates. Co5Zn1Ox, obtained by the incorporation of Zn species into the Co metal catalyst especially with a Co/Zn molar ratio of 5, could enhance the catalytic performances obviously compared to the sole Co catalyst. For example, the DMF, MF, and GVL yields reached up to 94, 98, and 77% during the catalysis by Co5Zn1Ox, which were much greater than 74, 0, and 23% for the Co catalyst, respectively. The enhanced performances of Co5Zn1Ox stem from the strong interaction between the Co and Zn species. Specifically, the presence of ZnO could stabilize Co2+ species, by offering electrons to Co species and creating oxygen vacancies, resulting in Co5Zn1Ox showing the highest adsorption amounts of furfural and furfuryl alcohol compared to Co1Zn1Ox and Co7Zn1Ox catalysts. Moreover, the catalyst showed good universality and reusability, and the HDO of 5-HMF to DMF proceeded in a true heterogeneous manner. The present work is believed to extend the application of bimetallic catalysts to the synthesis of bio-fuels and utilization of biomass materials.

N-heterocycles with quinoline and tetrahydroquinoline structures are highly important in pharmaceutical and chemical industries, and their highly efficient mutual transformations are vital but still challenging. In the present work, AlN supported redox cobalt catalysts (Co3O4/AlN and Co/AlN) were prepared, which could achieve the reversible aerobic oxidative dehydrogenation/hydrogenation of N-heterocycles with good performances. The catalytic performances were stem from the strong interaction between Co species with AlN support, which were confirmed by the characterizations of Raman, XPS, UV–vis DRS, and H2-TPR etc. Both of the catalysts showed good stabilities and reusabilities for the titled reactions. Besides, the gram-scale experiments achieved with good yields to corresponding products, revealing the present protocol possesses great potential applications in industry. The strategy of using redox Co-based catalyst not only provides a potential catalyst for the reversible hydrogenation/oxidative dehydrogenation reactions but also replenishes methods for constructing of other redox catalyst, especially with AlN as a carrier.