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.

A series of cerium-based UiO-66 was obtained via hydrothermal and sonochemical methods, using the same quantities of reagents (cerium ammonium nitrate (CAN), terephthalic acid (H₂BDC)) and solvents) in each synthesis. The impact of synthesis method and metal to linker ratio on the structural and textural properties of obtained UiO-66(Ce), as well as their composition in terms of Ce⁴⁺/Ce³⁺ ratio, structure defects resulting from missing linker, and CO₂ adsorption capacity was discussed. By using typical characterization techniques and methods, such as XRD, N₂ and CO₂ sorption, TGA, XPS, and SEM, it was shown that the agitation of reacting mixture during synthesis (caused by stirring or ultrasounds) allows to obtain structures that have more developed surfaces and fewer linker defects than when MOF was obtained in static conditions. The specific surface area was found to be of minor importance in the context of CO₂ adsorption than the contribution of Ce³⁺ ions that were associated with the concentration of linker defects.

The synthesis method of metal–organic frameworks (MOFs) has an important impact on their properties, including their performance in catalytic reactions. In this work we report on how the performance of [Cu₃(TMA)₂(H₂O)₃]_n (HKUST-1) and Ce@HKUST-1 in the reaction of CO oxidation depends on the synthesis method of HKUST-1 and the way the cerium active phase is introduced to it. The HKUST-1 is synthesised in two ways: via the conventional solvothermal method and in the presence of a cationic surfactant (hexadecyltrimethylammonium bromide (CTAB)). Obtained MOFs are used as supports for cerium oxide, which is deposited on their surfaces by applying wet and incipient wetness impregnation methods. To determine textural properties, structure, morphology, and thermal stability, the HKUST-1 supports and Ce@HKUST-1 catalysts are characterised using X-ray diffraction (XRD), N₂ sorption, scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), and thermogravimetric analysis (TGA). It is proven that the synthesis method of HKUST-1 has a significant impact on its morphology, surface area, and thermal stability. The synthesis method also influences the dispersion and the morphology of the deposited cerium oxide. Last but not least, the synthesis method affects the catalytic activity of the obtained material.

In this work, the carbon nanotubes (CNT)-supported nanosized, well-dispersed, CeZrO2 and Ni-CeZrO2 catalysts were obtained and tested for the first time in the reaction of methane dry reforming (DRM). The performance of the hybrid materials was compared with the performance of Ni/CNT catalyst. The mechanism of the DRM reaction and the occurrence of reverse water gas shift reaction (RWGS) and CO₂ deoxidation were discussed in terms of catalysts composition. The contribution of RWGS and CO₂ deoxidation in the DRM process, demonstrating an increased CO₂ consumption when compared to CH₄, and H₂/CO < 1, varied depending on the catalyst composition, was also studied.