MATTER AT EXTREMES

26 ESRF

[CuI(NH3)2]+ complexes. X-ray absorption spectroscopy (XAS) data, measured at BM23, show an almost complete reoxidation of CuI to CuII (84 ± 8 %). The newly formed CuII ions differ from the framework-interacting ones, as testified by XANES, EXAFS and UV-Vis (grey and red curves in Figure 13a-c), and are in agreement with the oxygen-bridged diamino dicopper (II) complexes, [Cu2(NH3)4O2]2+, proposed in the literature. EXAFS fitting based on different density functional theory (DFT)- optimised models points to a m-h2,h2-peroxo diamino dicopper (II) complex (Figure 13d, red box), in agreement with recent DFT predictions [3].

Wavelet Transform (WT) analysis further validates these findings. Based on the strong dependence of the backscattering

Structure and reactivity of oxygen-bridged diamino dicopper (II) complexes in Cu-Ion- Exchanged Chabazite Catalyst for NH3- Mediated Selective Catalytic Reduction, C. Negri (a), T. Selleri (b), E. Borfecchia (a), A. Martini (a,c), K.A. Lomachenko (d), T.V. Janssens (e), M. Cutini (a), S. Bordiga (a)

and G. Berlier (a), J. Am. Chem. Soc. 142, 15884-15896 (2020); https://doi. org/10.1021/jacs.0c06270. (a) Department of Chemistry and NIS Centre, University of Turin, Turin (Italy) (b) Dipartimento di Energia, Laboratorio di Catalisi e Processi Catalitici, Politecnico di

Milano, Milan (Italy) (c) Smart Materials, Research Institute, Southern Federal University, Rostov-on- Don (Russia) (d) ESRF (e) Umicore Denmark ApS, Hørsholm (Denmark)

[1] D.K. Pappas et al., J. Am. Chem. Soc. 139, 14961-14975 (2017). [2] K.A. Lomachenko et al., J. Am. Chem. Soc. 138, 12025-12028 (2016). [3] L. Chen et al., Phys. Chem. Chem. Phys. 21, 10923-10930 (2019). [4] I.A. Pankin et al., Catal. Today 345, 125-135 (2020).

PRINCIPAL PUBLICATION AND AUTHORS

REFERENCES

amplitude factors F(k) on the atomic number Z (Figure 14a), a 2D representation of the EXAFS in R- and k-space, obtained by WT, discriminates the contribution of Cu with respect to lighter atoms [4]. Indeed, the 2D plots show a sublobe around k = 7 Å 1 unambiguously related to a Cu Cu scattering contribution, after pre-treatment in O2 (Figure 14b) and reaction with O2 after the reduction with NO/NH3 (Figure 14d), which is not observed for [CuI(NH3)2]+ complexes (Figure 14c). The different shape of this feature points to a uniform Cu Cu interatomic distance in the m-h2,h2-peroxo diamino dicopper (II) complexes, and to a heterogeneous mixture of multi-copper species in the pre-treated Cu-CHA catalyst. This is the first experimental evidence of the structure of well-defined biomimetic oxygen-bridged diamino dicopper complexes in zeolites, predicted by DFT calculations [3].

Fig. 14: a) Backscattering amplitude factors of relevant

atoms. Moduli of EXAFS WTs in the 2 4 Å R-space range for

(b) pre-treatment in O2, (c) reduction in NO/NH3,

(d) subsequent reaction with O2, including the corresponding

EXAFS spectra in k- and R-space (conventional FT).