Direct hydrogenation of CO₂ to methanol is an interesting method to recycle CO₂ emitted e.g., during combustion of fossil fuels. However, it is a challenging process because both the selectivity to methanol and its production are low. The metal-organic frameworks are relatively new class of materials with a potential to be used as catalysts or catalysts supports, also in the reaction of MeOH production. Among many interesting structures, the UiO-66 draws significant attention owing to its chemical and thermal stability, developed surface area, and the possibility of tuning its properties e.g., by exchanging the zirconium in the nodes to other metal cations. In this work we discuss—for the first time—the performance of Cu supported on UiO-66(Ce/Zr) in CO₂ hydrogenation to MeOH. We show the impact of the composition of UiO-66-based catalysts, and the character of Cu-Zr and Cu-Ce interactions on MeOH production and MeOH selectivity during test carried out for 25 h at T = 200 °C and p = 1.8 MPa. Significant increase of selectivity to MeOH was noticed after exchanging half of Zr⁴⁺ cations with Ce⁴⁺; however, no change in MeOH production occurred. It was found that the Cu-Ce coexistence in the UiO-66-based catalytic system reduced the selectivity to MeOH when compared to Cu/UiO-66(Zr), which was ascribed to lower concentration of Cu⁰ active sites in Cu/UiO-66(Ce/Zr), and this was caused by oxygen spill-over between Cu⁰ and Ce⁴⁺, and thus, the oxidation of the former. The impact of reaction conditions on the structure stability of tested catalyst was also determined.

Herein, we report monometallic Ni and bimetallic Pd–Ni catalysts supported on CeO₂–Al₂O₃ binary oxide which are highly active and selective in oxy-steam reforming of methanol (OSRM). Monometallic and bimetallic supported catalysts were prepared by an impregnation method. The physicochemical properties of the catalytic systems were investigated using a range of methods such as: Brunauer–Emmett–Teller (BET), X-ray Powder Diffraction (XRD), Temperature-programmed reduction (TPR–H₂), Temperature-programmed desorption (TPD–NH₃), X-ray photoelectron spectroscopy (XPS) and Scanning Electron Microscope equipped with an energy dispersive spectrometer (SEM–EDS). We demonstrate that the addition of palladium facilitates the reduction of nickel catalysts. The activity tests performed for all catalysts confirmed the promotion effect of palladium on the catalytic activity of nickel catalyst and their selectivity towards hydrogen production. Both nickel and bimetallic palladium–nickel supported catalysts showed excellent stability during the reaction. The reported catalytic systems are valuable to make advances in the field of fuel cell technology.

Copper and gold doped copper catalysts supported on multi-walled carbon nanotubes were prepared by wet impregnation and deposition–precipitation methods, respectively.

The photocatalytic activity of TiO₂ depends on numerous factors, such as the chemical potential of electrons, charge transport properties, band-gap energy, and concentration of surface-active sites. A lot of research has been dedicated to determining the properties that have the most significant influence on the photocatalytic activity of semiconductors. Here, we demonstrated that the activity of TiO₂ in the gas-phase reduction of CO₂ is governed mainly by the desorption rate of the reaction intermediates and final products. This indicates that the specific surface area of TiO₂ and binding strength of reaction intermediates and products are the main factors affecting the photocatalytic activity of TiO₂ in the investigated process. Additionally, it was shown that rutile exhibits higher photocatalytic activity than anatase/rutile mixtures mainly due to its high efficiency in the visible portion of the electromagnetic spectrum.