The use of UV-visible light responsive catalysts in hydrogen production is of high interest owing to reduced energy and environment resources. Here, we present a highly efficient system for photocatalytic hydrogen production, comprising ordered silicate nanochannels embedded with novel visible-light-responsive catalytic phosphotungstic acids (PTA) along the silicate channel walls and arrayed co-catalytic platinum nanoparticles within the channels. The UV-visible-light-responsive PTA catalyst is synthesized by replacing a corner WO⁴⁺ of PTA with Ni for Ni-ℓPTA, and then embedded onto the walls of hexagonally packed silicate channels during synthesis at an air-liquid interface. In situ grazing incidence small-angle X-ray scattering on the air-liquid interface [1-2] evidences multi-step formation processes of the ordered and oriented silicatropic template PMS and the subsequent formation of Pt NP arrays in the PMS template. Suggested by the X-ray results, the latter process involves anion exchange of the Pt-metal precursors and the surfactant micelles of the silicate PMS channels, upon UV-visible light irradiation. The hence formed composite Pt-NP@Ni-ℓPMS, with closely packed catalytic pairs of Pt-NP and PTA, demonstrates a high hydrogen production rate upon light illumination, due presumably to efficient generation and transport of photo-electrons. The efficiency of H₂-production surpasses greatly that of PMS or Ni-ℓPMS with or without randomly disperse Pt nanoparticles.

Controlling the mesoscopic nature of materials through local interactions can lead to the formation of highly non-topologically trivial structures. The local interactions that lead to the emergence of mesoscopic structures, known as textures, is well understood in magnetic materials. The most studied textures are skyrmions as the have interesting applications in spintronics due to their topological nature and dynamic properties [1]. These features are thought to be exclusively a magnetic characteristic; however, they are purely topological in nature and arise due to a specific set of interactions which may not be limited to magnetic materials. As we have an increased understanding of what causes topological properties, we can design/search for specific interactions in non-magnetic materials that may lead to non-magnetic analogues of topologically protected phases.

For skyrmions to exist, three interactions must be present: symmetric exchange, antisymmetric exchange, and a coupling to a magnetic field [2]. To explore the possibility of creating analogues of magnetic textures in non-magnetic materials we replace magnetic dipoles with non-magnetic quadrupoles and exchange the magnetic field for a strain field and adapt the interactions accordingly. Here we look at the capability of MOFs to harbor analogous complex magnetic phases such as skyrmions. MOFs are the perfect candidates as there are a plethora of components to play with such as underlying lattice, guest species, and interactions between the framework and the guest.

Through density functional theory calculations, molecular dynamics simulations, and Monte Carlo simulations, we explore the extent to which these interactions may exist in chiral MOF frameworks with quadrupolar guests such as a benzene or CO₂ and how varying the relative strengths of the three interaction parameters with temperature effects the behaviour of the non-magnetic textures. Using small angle scattering we have been able to define six distinct phases, giving evidence of quadrupolar skyrmions and interesting textures which are not present in the dipolar analogue. This opens up the field to new ways of creating non-topologically trivial textures that could potentially be less restrictive than chiral magnets.

[1] S. Mühlbauer, B. Binz, F. Jonietz, C. Pfleiderer, A. Rosch, A. Neubauer, R. Georgii, and P. Boni, Science 323, 915 (2009).

[2] S. D. Yi, S. Onoda, N. Nagaosa, and J. H. Han, Phys. Rev. B. 80, 054416 (2009).

Artificial molecular machines promise applications in many fields, including physics, information technologies, chemistry as well as medicine. The deposition of functional molecules in 2D or 3D assemblies in order to control their collective behavior and the structural characterization of these assemblies are challenging tasks. We exploit porous materials to form rigid matrix for mechanochemical preparation of bulk or surface host−guest inclusions with functional molecules, such as molecular rotors, molecular motors and molecular switches.

Unambiguous determination of the molecular structure and monitoring of the molecular function such as rotation of a molecular rotor or on/off switching of a molecular switch cannot be studied by X-ray analysis because the systems are typically heavily disordered fine powders. We use solid-state nuclear magnetic resonance (SS-NMR) spectroscopy to obtain atomic-level insights into the structure and dynamics of these functional materials. SS-NMR spectra provide valuable information about structure, interactions and dynamics in solids not available otherwise.

It will be demonstrated that SS-NMR experiments provide unequivocal evidence of the formation of the 2D and 3D assemblies and can also be used for the observation of such a molecular function as the photoisomerization of a molecular switch deposited on a surface. We have also developed a solid-state NMR method for investigation of two dimensional arrays of light-driven molecular motors [1-4].

Figure 1. Examples of studied molecules. The shaft ensures deposition of the molecules in the porous molecular matrix, the stopper ensures surface deposition. The molecular motor is a unidirectional light-driven motor and the switch performs its function upon UV irradiation.

[1] Kaleta, J., Chen, J., Bastien, G., Dračínský, M., Mašát, M., Rogers, C. T., Feringa, B. L., Michl, J. (2017). J. Am. Chem. Soc. 139, 10486.

[2] Kaleta, J., Bastien, G., Wen, J., Dračínský, M., Tortorici, E., Císařová, I., Beale, P. D., Rogers, C. T., Michl, J. (2019). J. Org. Chem. 84, 8449.

[3] Santos-Hurtado, C., Bastien, G., Mašát, M., Štoček, J. R., Dračínský, M., Rončević, I., Císařová, I., Rogers, C., Kaleta, J. (2020). J. Am. Chem. Soc. 142, 9337.

[4] Dračínský, M., Santos-Hurtado, C., Masson, E., Kaleta, J. (2021). Chem. Commun. 57, 2132.

CO₂ is widely recognised as the main cause of greenhouse effect, causing global warming and climate change. With the aim to reduce CO₂ emissions, during the last decades, several strategies have been developed for the capture, utilization and storage of carbon dioxide (CCUS). This work focuses on the development of bifunctional catalysts for the conversion of CO₂ into dimethyl ether (DME), a fuel with no collateral emissions other than CO₂ and H₂O, a high cetane number and chemical-physical properties similar to LPG. DME is obtained from the reaction of CO₂ with H₂ through two subsequent reactions. The first one is the CO₂ reduction with H₂ to obtain methanol; this reaction is promoted by Cu-based catalysts like Cu/ZnO/Al₂O₃ and Cu/ZnO/ZrO₂. The second one is the dehydration of methanol to DME, catalysed by solid acidic catalysts, such as zeolites and γ-Al₂O_3.

In this work three different types of mesostructured acidic catalysts were synthesized: Al-SiO₂ (Al-SBA-15, Al-MCM-41), Zr-TiO₂ and γ-Al₂O₃. These materials were tested for methanol dehydration and used as supports for the Cu-based redox phase, to obtain composite materials to be used as bifunctional catalysts. Mesostructured matrix should limit the growth of redox phase nanoparticles inside the mesopores and assure a high dispersion due to the high surface area, leading to a high contact area between the two phases and, thus, granting in principle superior catalytic performances.

All mesostructured systems were synthesized via the Sol-Gel method, either through an Evaporation-Induced Self-Assembly (EISA) or a solvothermal approach, and characterized by XRD, TEM and N₂ physisorption. Acidic sites characterization was performed by calorimetry and FTIR spectroscopy using pyridine as a probe molecule. The catalysts were eventually physically mixed with a Cu/ZnO/Al₂O₃-based commercial redox catalyst and tested in a bench-scale plant with a fixed bed reactor for CO₂ conversion to DME. Mesostructured supports were used to disperse the CuO/ZnO/ZrO₂-based redox phase by a wet impregnation method combined with a self-combustion process or by a two-solvents impregnation strategy. The obtained bifunctional catalysts were characterized by PXRD, N₂ physisorption, TEM and HRTEM in order to determine the most promising synthetic conditions in terms of dispersion and nanosize of the active phase and textural properties of the corresponding composites.