Co@NH2-MIL-125(Ti): Cobaloxime-derived Metal-Organic Framework-based Composite for Light-driven H2 Production Nasalevich, M.A.; Becker, R.; Ramos-Fernandez, E.V.; Castellanos, S.; Veber, S.L.; Fedin, M.V.; Kapteijn, F.; Reek, J.N.H.; van der Vlugt, J.I.; Gascon, J. Disclaimer/Complaints regulationsIf you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library: http://uba.uva.nl/en/contact, or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible. We present a synthetic strategy for the efficient encapsulation of a derivative of a well-defined cobaloxime proton reduction catalyst within a photoresponsive metal-organic framework (NH 2 -MIL-125(Ti)). The resulting hybrid system Co@MOF is demonstrated to be a robust heterogeneous composite material. Furthermore, Co@MOF is an efficient and fully recyclable noble metal-free catalyst system for lightdriven hydrogen evolution from water under visible light illumination. Broader contextThe development of new strategies for the efficient valorization of solar light is one the most important challenges we face nowadays. Among the different possibilities, dihidrogen molecule is considered as one of the possible future energy carriers allowing for CO 2 -free energy cycle. Although the photocatalytic water splitting was the rst photocatalytic reaction to be discovered, no photocatalytic systems for this reaction have been industrially applied. This is both due to the fact that most discovered catalysts rely on the use of noble metals and to the low activities achieved so far by alternative catalysts. The application in this eld of materials such as metal-organic frameworks (MOFs) can be a game changer in this research eld. MOFs have been proven to be photoactive and their optical properties can be easily tuned towards visible light operation. The current challenge lies in the development of more appropriate active sites for the desired photocatalytic cycle. In this manuscript, we report a new strategy to achieve this goal. By introducing a derivative of the well-known molecular Co-based electrocatalyst Co-dioxime-diimine into the pores of a photo-active NH 2 -MIL-125(Ti) following a 'Ship-in-a-bottle' strategy, we were able to synthesize a highly active photocatalyst composite free of noble metals, and fully recyclable. Because of the novelty and the implications of this work, we feel that it might appeal to the interdisciplinary readership of energy and environmental science. The journal has previously been an important forum for the research topics touched upon in this paper (new earth abundant materials and their application in (photo) catalysis and hydrogen evolution from water under visible light illumination). We would be glad t...

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Synthesis and characterization of new carbazolyl derivatives with a pendant stable radical of the TTM (tris-2,4,6-trichlorophenylmethyl radical) series are reported. The EPR spectra, electrochemical properties, absorption spectra, and luminescent properties of these radical adducts have been studied. All of them show electrochemical amphotericity being reduced and oxidized to their corresponding stable charged species. The luminescence properties of them cover the red spectral band of the emission. The luminescence of the electron-rich carbazole adducts shows the donor-acceptor nature of the excited state. On the other hand, the EPR parameters of these radical adducts show an imperceptible variation with the substituents in the carbazole.

Progress and challenges in the development of photo-responsive metal organic frameworks.

The ability to control the interplay of materials with low-energy photons is important as visible light offers several appealing features compared to ultraviolet radiation (less damaging, more selective, predominant in the solar spectrum, possibility to increase the penetration depth). Two different metal-organic frameworks (MOFs) were synthesized from the same linker bearing all-visible ortho-fluoroazobenzene photoswitches as pendant groups. The MOFs exhibit different architectures that strongly influence the ability of the azobenzenes to isomerize inside the voids. The framework built with Al-based nodes has congested 1D channels that preclude efficient isomerization. As a result, local light-heat conversion can be used to alter the CO2 adsorption capacity of the material on exposure to green light. The second framework, built with Zr nodes, provides enough room for the photoswitches to isomerize, which leads to a unique bistable photochromic MOF that readily responds to blue and green light. The superiority of green over UV irradiation was additionally demonstrated by reflectance spectroscopy and analysis of digested samples. This material offers promising perspectives for liquid-phase applications such as light-controlled catalysis and adsorptive separation.

Recently, MIL-125(Ti) and NH2 -MIL-125(Ti), two titanium-based metal-organic frameworks, have attracted significant research attention in the field of photocatalysis for solar fuel generation. This work reveals that the differences between these structures are not only based on their light absorption range but also on the decay profile and topography of their excited states. In contrast to MIL-125(Ti), NH2 -MIL-125(Ti) shows markedly longer lifetimes of the charge-separated state, which improves photoconversion by the suppression of competing decay mechanisms. We used spectroelectrochemistry and ultrafast spectroscopy to demonstrate that upon photoexcitation in NH2 -MIL-125(Ti) the electron is located in the Ti-oxo clusters and the hole resides on the aminoterephthalate unit, specifically on the amino group. The results highlight the role of the amino group in NH2 -MIL-125(Ti), the electron donation of which extends the lifetime of the photoexcited state substantially.

Extreme ultraviolet (EUV) lithography (13.5 nm) is the newest technology that allows high-throughput fabrication of electronic circuitry in the sub-20 nm scale. It is commonly assumed that low-energy electrons (LEEs) generated in the resist materials by EUV photons are mostly responsible for the solubility switch that leads to nanopattern formation. Yet, reliable quantitative information on this electron-induced process is scarce. In this work, we combine LEE microscopy (LEEM), electron energy loss spectroscopy (EELS), and atomic force microscopy (AFM) to study changes induced by electrons in the 0−40 eV range in thin films of a state-of-the-art molecular organometallic EUV resist known as tin-oxo cage. LEEM−EELS uniquely allows to correct for surface charging and thus to accurately determine the electron landing energy. AFM postexposure analyses revealed that irradiation of the resist with LEEs leads to the densification of the resist layer because of carbon loss. Remarkably, electrons with energies as low as 1.2 eV can induce chemical reactions in the Sn-based resist. Electrons with higher energies are expected to cause electronic excitation or ionization, opening up more pathways to enhanced conversion. However, we do not observe a substantial increase of chemical conversion (densification) with the electron energy increase in the 2−40 eV range. Based on the dose-dependent thickness profiles, a simplified reaction model is proposed where the resist undergoes sequential chemical reactions, first yielding a sparsely cross-linked network and then a more densely cross-linked network. This model allows us to estimate a maximum reaction volume on the initial material of 0.15 nm 3 per incident electron in the energy range studied, which means that about 10 LEEs per molecule on average are needed to turn the material insoluble and thus render a pattern. Our observations are consistent with the observed EUV sensitivity of tin-oxo cages.

, "Photochemical conversion of tin-oxo cage compounds studied using hard x-ray photoelectron spectroscopy," J. Micro/Nanolith. MEMS MOEMS 16(2), 023510 (2017), doi: 10.1117/1.JMM.16.2.023510. Abstract. Molecular inorganic materials are currently considered photoresists for extreme ultraviolet lithography (EUVL). Their high EUV absorption cross section and small building block size potentially allow high sensitivity and resolution as well as low line-edge roughness. The photochemical reaction mechanisms that allow these kinds of materials to function as photoresists, however, are still poorly understood. We discuss photochemical reactions upon deep UV (DUV) irradiation of a model negative-tone EUV photoresist material, namely the welldefined molecular tin-oxo cage compound ½ðSnBuÞ 12 O 14 ðOHÞ 6 ðOHÞ 2 , which is spin-coated to thin layers of 20 nm. The core electronic structures (Sn 3d, O 1s, and C 1s) of unexposed and DUV exposed films were then investigated using synchrotron radiation-based hard x-ray photoelectron spectroscopy. Different chemical oxidation states and concentrations of atoms and atom types in the unexposed and exposed films were found. We observed that the exposure in a nitrogen atmosphere prevented the oxidation but still led to carbon loss, albeit with a smaller conversion. Finally, a mechanistic hypothesis for the basic DUV photoreactions in molecular tin-oxo cages is proposed. © The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.