| AVS 62nd International Symposium & Exhibition | |
| In-Situ Spectroscopy and Microscopy Focus Topic | Monday Sessions |
| Session IS+AS+SS-MoM |
| Session: | Fundamental Studies of Surface Chemistry of Single Crystal and Nanomaterials under Reaction Conditions |
| Presenter: | Niclas Johansson, Lund University, Sweden |
| Authors: | N. Johansson, Lund University, Sweden S. Chaudhary, Lund University, Sweden A.R. Head, Lund University, Sweden O. Snezhkova, Lund University, Sweden J.N. Andersen, Lund University, Sweden J. Knudsen, Lund University, Sweden J. Schnadt, Lund University, Sweden |
| Correspondent: | Click to Email |
Surface-immobilization of transition metal complexes otherwise used as homogeneous catalysts, i.e. in the same (solution) phase as the reactants and products, and their use as heterogeneous catalysts has been an active field of research for many years. The attractiveness of the idea of surface-immobilization lies in the potential to significantly increase the efficiency and selectivity of heterogeneous catalysts [1], the ease of catalyst and product separation [1], and the fact that the need for solvents and highly oxidizing agents might be eliminated in the heterogeneous system.
Here we direct our attention towards the transition metal Mn(III)-salen complex[R,R(-)N,N’Bis(3,5-di-t-butylsalicylidene, 1,2-cyclohexane diaminomanganese(III)chloride) which have been shown to be very effective homogeneous catalysts for enatioselective epoxidation of unfunctionalised olefins. Yet, while much research has been done to investigate the salen complexes’ catalytic properties in the homogeneous phase, very few surface science studies have been performed [2,3].
Here we report a study starting from standard UHV conditions and bridging the pressure gap into more realistic conditions. Here, we will show UHV spectra coupled to Torr-range Ambient Pressure X-ray Photoelectron Spectroscopy (APXPS).
We investigated propylene(C2H6) epoxidation reaction using surface-deposited Mn(III)-Salen on Au(111) as catalyst. With APXPS we were able to follow the electronic structure changes during reaction conditions in a gas mixture of propylene and oxygen. The spectra acquired show gas phase interactions and changes was found that were specific to the gas mixture. Surprisingly, O 1s spectra acquired at room temperature shows CO2 which indicates complete oxidation of propylene. This result was further confirmed with a mass spectrometer in direct connection with the reaction chamber. Indeed, the complexes are active even in a heterogeneous system supporting the possibility of transferring homogeneous catalysts into heterogeneous catalytical systems.
References
[1] C. Copéret and J.-M. Basset, Adv. Synth. Catal. 349 , 78 (2007)
[2] K. Lämel et al, Nano Lett. 10, 2965 (2010)
[3] A. Schwartz et al., J. Phys. Chem. C 117, 1105 (2013)