Bebensee, F.

Nefedov, A.

Wöll, C.

Yang, C.

English

KITopen

KIT – University of the State of Baden-Wuerttemberg andNational Research Center of the Helmholtz AssociationAdsorption and Dehydrogenation ofTetrahydroxybenzene on Cu(111) and Ni(111) Fabian Bebensee1, Chengwu Yang1,2, Alexei Nefedov1, Christof Wöll1MotivationSurface functionalization in the form of two-dimensional networks is a method of growing interest for the development offunctional, periodic nanometer-scale structures with. great potential in catalysis, for example. A common problem ingeneration of such structures is that more stable covalent assemblies are prone to structural defects limiting the achievabledegree of order, while highly ordered hydrogen-bonded structures often lack the necessary stability. Metal Organic Networksare intermediate between those two types of structures. They posses quite interesting 3D-analgoues, Metal OrganicFrameworks.Tetrahydroxybenzene (THB) was recently found to dehydrogenate on Cu(111) [1] and form a regular network consisting of acompletely dehydrogenated THB species and Cu-adatoms [2]. Interestingly, STM and XPS investigations showed that thenodes of this network consist of Cu-trimers, where each Cu-atom is bonded to two dehydrogenated THB-molecules via theiroxygen atoms. With such a complex node, this network is a very realistic truly two-dimensional MOF analogue that allows toexploit the surface-science toolkit to investigate MOF-like structures. Furthermore, the generation of monodispersed andvery small metal (oxide) clusters is of great interest in the area of catalysis.References[1] F. Bebensee, K. Svane, C. Bombis, F. Masini, S. Klyatskaya, F. Besenbacher, M. Ruben, B. Hammer, T. Linderoth, Adsorption and Dehydrogenation of Tetrahydroxybenezene on Cu(111), Chem. Commun. 2013, 49, 9308-9310.[2] F. Bebensee, K. Svane, C. Bombis, F, Masini, S. Klyatskaya, F. Besenbacher, M. Ruben, B. Hammer, T. Linderoth,   A Surface Coordination Network Based on Copper Adatom Trimers, Angew. Chem. Int. Ed. 2014, 53, 12955-12959.1Institute of Functional Interfaces2Helmholtz Research School „Energy-related catalysis“Introduction and AimsScheme 1: Stepwise dehydrogenation of THB yielding first dihydroxy-benzoquinone (DHBQ) and then a 2,5-dioxy-p-benzosemiquinonediradical on the Cu(111) surface.Figure 1: STM images showing extended network islands (left)and the Cu-trimer nodes in high resolution (right).Figure 2: DFT-derived network structure (left) and coordinationgeometry of individual molecular building block (right).1. Details of the electronic structure of the network on Cu(111)2. Explore other surfaces for network formation, particularly Ni(111)Aims:The network formed by the dehydrogenated THB on Cu(111)is interesting for its unusual threefold-coordination motif: themonodisperse Cu-trimers may be interesting in catalysis andthe structure effectively mimics a truly 2-D MOF. For thesereasons, a more detailed characterization of the Cu-nodes isobviously highly desirable, yet experimentally challengingdue to the signal arising from surface Cu-atoms.275 280 285 290 295 300 Intensity / Arb. Units  Binding Energy / eV THB dosed at low T THB annealed to 370 K THB annealed to 440 KMultilayerXPSC 1s525 530 535 540 545 Intensity / Arb. UnitsBinding Energy / eV THB dosed at low T THB annealed to 370 K THB annealed to 440 KXPSO 1sC=OC-O-H65 70 75 80 85 90XPSCu 3p THB dosed at low T THB annealed to 370 K THB annealed to 440 K Clean Cu(111) Intensity / Arb. UnitsBinding Energy / eV270 280 290 300 310 320 3300.00.51.01.52.02.53.03.5  Intensity / Arb. UnitsPhoton energy / eV 30° 55° 90°NEXAFSC-edge270 280 290 300 310 320 3300.00.51.01.52.02.53.0NEXAFSC-edge  Intensity / Arb. UnitsPhoton energy / eV 30° 55° 90°270 280 290 300 310 320 3300.00.51.01.52.02.53.03.5NEXAFSC-edge  Intensity / Arb. UnitsPhoton Energy / eV 30° 55° 90°as prepared annealed to 370 K annealed to 440 K520 530 540 550 560 570 5800.00.51.01.52.02.53.03.5 NEXAFSO-edge  Intensity / Arb. UnitsPhoton energy / eV 30° 55° 90°520 530 540 550 560 570 5800.00.51.01.52.02.53.03.5 NEXAFSO-edgeIntensity / Arb. UnitsPhoton energy / eV 30° 55° 90°520 530 540 550 560 570 5800.00.51.01.52.02.53.03.5 NEXAFSO-edgeIntensity / Arb. UnitsPhoton energy / eV 30° 55° 90°as prepared annealed to 370 K annealed to 440 KTHB on Cu(111) Preparation routine is robust and applicable at the HESGM-endstation Molecular adsorption at low temperature, even formation of multilayers Progressing dehydrogenation with increasing temperature (cf. [1], [2]) Clear correspondence of spectral features to dehydrogenation state Should provide a more detailed picture in conjunction with modelling Angular dependence suggests planar adsorption geometryXPSNEXAFSTHB on Ni(111)275 280 285 290 295 300XPSC 1s  Intensity / Arb. UnitsBinding Energy / eV 300 K 450 K520 525 530 535 540XPSO 1s  Intensity / Arb. UnitsBinding Energy / eV 300 K 450 K XPS indicates drastically different dehydrogenation product!Quality of NEXAFS-data clearly not satisfactory (not shown)• Different dehydrogenation states can be studied using NEXAFS Complete with simulations and experiments on high density phase on Cu(111)• Ni(111) is not a suitable substrate for network formation! Investigate other promising candidates, e.g. Pt(111) Acquire missing NEXAFS data to rationalize failure of network formationExperimental The Ni(111) and Cu(111) substrates were prepared via sputter-anneal cycles untilXPS showed no carbon contamination and a clear LEED pattern was observed THB molecules (provided by Dr. M Tsotsalas) were sublimated onto clean Ni(111)and Cu(111) substrates held at 110 K from a home-built Knudsen cell at 330 K. The sample transfer to the analysis chamber after preparation lead to only amoderate increase of the sample temperature (below 15 K). After characterization of the as prepared samples, the respective samples wereannealed for 20 minutes at the stated temperatures in order to achieve thedesired dehydrogenation. The subsequent measurements were performed afterre-cooling the sample to 110 K.All experiments reported were carriedout at the HESGM-endstation shown inthe picture to the left.The endstation provides a preparationchamber for sputtering and annealing.It is furthermore equipped with a LEEDoptics to check the surface structure.The attached analysis chamber allowsfor NEXAFS and XPS experimentsusing a home-build detector and ahemispherical analyzer, respectively.Conclusions and Outlook

Adsorption and dehydrogenation of tetrahydroxybenzene on Cu(111) and Ni(111)

https://publikationen.bibliothek.kit.edu/220098081/3816703

Adsorption and dehydrogenation of tetrahydroxybenzene on Cu(111) and Ni(111)

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