Best-fit parameters optimized by EXAFS fits of the k3-weighted spectrum of activated copper-exchanged mordenite with different copper loadings. DFT-optimized geometry for dicopper mono-μ-oxo sites located in the 8-membered ring of MOR was used as the starting guess. The fit was performed in R-space in the range of 1.0–3.0 Å, employing the k-range of 3.0–16.0 Å−1 for the FT, resulting in a number of independent points Nind > 16.
| Parameter | Scatter | Cu(4.3)MOR(6) | Cu(3.5)MOR(6) | Cu(3.2)MOR(6) | Cu(2.5)MOR(6) | Cu(1.7)MOR(6) |
|---|---|---|---|---|---|---|
| ΔE, eV | +1.7(6) | +2.1(6) | +2.6(7) | +1.4(12) | +1.5(12) | |
| N O | O | 3.9(2) | 3.8(1) | 3.6(2) | 3.6(3) | 3.7(3) |
| R(Cu–O), Å | 1.938(3) | 1.940(3) | 1.944(3) | 1.933(1) | 1.93(2) | |
| Debye–Waller factor, 10−3 Å2 | 6.8(4) | 6.1(3) | 6.0(4) | 6.4(6) | 6.1(6) | |
| N Al | Al or Si | 1.8(7) | 1.6(3) | 1.5(3) | 1.1(6) | 1.2(7) |
| R(Cu–Al, Si), Å | 2.69(2) | 2.66(1) | 2.67(1) | 2.66(2) | 2.66(2) | |
| Debye–Waller factor, 10−3 Å2 | 11.3(60) | 8.3(21) | 7.5(20) | 8.0(49) | 8.6(58) | |
| N Cu | Cu | 0.3(4) | 0.2(2) | 0.1(1) | 0.4(5) | 0.3(4) |
| R(Cu–Cu), Å | 2.86(3) | 2.86(1) | 2.87(1) | 2.88(3) | 2.85(2) | |
| Debye–Waller factor, 10−3 Å2 | 7.1(68) | 4.6(36) | 2.7(33) | 7.6(77) | 5.1(20) | |
| R-factor | 0.0022 | 0.0021 | 0.0031 | 0.0089 | 0.0098 | |
| χ 2-parameter | 111 | 95 | 73 | 64 | 83 | |