Molecular photoswitches triggered with red or NIR light are optimal for photomodulation of complex biological systems, including efficient penetration of the human body for therapeutic purposes ("therapeutic window"). Yet, they are rarely reported, and even more rarely functional under aqueous conditions. In this work, fluorinated azobenzenes are shown to exhibit efficient E!Z photoisomerization with red light (PSS 660nm > 75 % Z) upon conjugation with unsaturated substituents. Initially demonstrated for aldehyde groups, this effect was also observed in a more complex structure by incorporating the chromophore into a cyclic dipeptide with propensity for selfassembly. Under physiological conditions, the latter molecule formed a supramolecular material that reversibly changed its viscosity upon irradiation with red light. Our observation can lead to design of new photopharmacology agents or phototriggered materials for in vivo use.

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On a Ni/Al 2 O 3 and a NiÀ Fe/Al 2 O 3 catalyst spatial concentration and temperature profiles were determined that occur along the axial direction of the catalyst bed. They were correlated to structural gradients under reaction conditions to elucidate the local dependency of catalyst structure on reaction-induced changes of the gas phase. The quantitative concentration and temperature profiles revealed a hotspot in the first third part of the fixed-bed, which led to by-product formation of CO. Complementary structural information obtained by spatiallyresolved quick X-ray absorption spectroscopy unraveled a strong impact of reaction-induced gradients in gas phase on the oxidation state of Fe with a higher oxidation state towards the end of the catalyst bed, while Ni was only slightly affected. Diffuse reflectance infrared Fourier transform spectroscopy further revealed that addition of Fe to a Ni/Al 2 O 3 catalyst reduces the amount of adsorbed CO species. Hence, Fe hampers blocking of active Ni 0 sites by CO and preserves a high fraction of reduced Ni species. Furthermore, an alternative reaction pathway observed on NiÀ Fe provided locally a higher activity for CO 2 hydrogenation. Overall, the importance of considering local gradients in catalytic reactors is demonstrated.Recently, promising bimetallic NiÀ Fe-based catalysts gained broad attention as they offer enhanced catalytic activity and stability under stationary and fluctuating CO 2 methanation conditions. [17][18][19][20][21][22] Hence, several studies have been conducted focusing on unraveling the promoting role of Fe. Various studies orient to the Ni : Fe ratio 3 : 1, proposed for CO methanation [23][24] and also found active in CO 2 methanation. [17][18][19]22,[24][25][26][27] Notably, it was reported that the NiÀ Fe alloy is structurally instable during CO 2 methanation: Ni remains reduced while Fe is oxidized. [19,21,28] By conducting extensive ex situ studies Burger et al. [29] suggested a migration of Fe from the alloy to the particle surface. Thereby, Fe is (partly) oxidized to Fe 2 + . They assumed that this provides new redox sites for enhanced CO 2 activation. [29] Complementary operando characterization including modulation excitation spectroscopy has recently confirmed this speculation. [30] Highly dynamic FeO x clusters were found to be formed on top of the NiÀ Fe alloy particles under CO 2 methanation conditions. These FeO x clusters exhibit a Fe 0 * * Fe 2 + * * Fe 3 + redox behavior thereby providing active sites for enhanced CO 2 adsorption and dissociation. In addition, the FeO x clusters protect and/or clean the Ni surface from oxygen impurities and thereby retain the active Ni 0 sites for H 2 dissociation. [20] DFT calculations further uncovered that CO 2 and H 2 O show a very low tendency for oxidation of Ni [a] M.

Understanding catalyst deactivation is important for future knowledge-based design of catalysts with improved stability. Deactivation by thermal aging is particularly relevant for exothermic reactions, here demonstrated with CO2 methanation using...

The Cover Feature illustrates the gradients in structure and activity along a catalytic fixed‐bed reactor during CO2‐methanation. In the focus of this study are Ni‐based catalysts. In their Full Paper, by combining spatial activity profiling and complementary structural X‐ray absorption spectroscopic studies, M.‐A. Serrer, M. Stehle et al. uncovered relationships between the course of the reaction including gas phase concentration and the structure of the catalysts. In case of a bimetallic Ni‐Fe‐catalyst, a strong correlation between Fe oxidation state and the amount of water in the gas atmosphere was found. An oxidation of Fe under formation of FeOx species is able to protect the active Ni0 centers from oxidation and can offer an alternative CO2 activation pathway. Compared to a conventional Ni‐based catalyst, this results in higher activity and selectivity. More information can be found in the Full Paper by M.‐A. Serrer, M. Stehle et al.