Table 1. Co–Xgas distances and differential enthalpies of adsorption (Δh ad) of CO, CO2, CH4, N2, O2, and Ar in Co2(dobdc).
| Gas | d(Co–Xgas) (Å) | Δd a (Å) | –Δh ad b (kJ mol–1) |
| CO | 2.215(6) (Co–C) | –0.230(6) | 48.8(2)40 |
| CO2 | 2.261(9)29 (Co–O) c | –0.004(9) | 33.6(1)29 |
| N2 | 2.236(6) (Co–N) | –0.059(6) | 20.3(6) |
| O2 | 2.216(5) (Co–O) | –0.049(5) | 18.56(3) |
| CH4 | 2.941(19) (Co···C) | — | 19.21(9) |
| Ar | 2.932(9) (Co–Ar) | 0.307(9) | 17(1) |
aΔd = the Co–Xgas distance minus the sum of the ionic radius for high-spin cobalt(ii)107 and the van der Waals radius of the coordinated atom. Δd was not calculated for CH4 because the Co···C distance is between Co and the central atom of CH4, not the coordinated hydrogen atoms, which makes it difficult to compare rigorously with the other gases.
bLow-coverage differential enthalpies of adsorption were calculated at a loading of 0.5 mmol g–1 using independent Langmuir fits to low-pressure adsorption isotherms.
cAlthough the structure of CO2 in Co2(dobdc) was collected at a higher temperature (150 K) compared to the other structures (90 and 100 K), the Co–OCO2 distance (2.23(4) Å) obtained at 10 K from powder neutron diffraction data shows that the Co–OCO2 distance does not shorten significantly at lower temperatures.29