Correction: CO2 induced phase transitions in diamine-appended metal–organic frameworks

Correction for ‘CO2 induced phase transitions in diamine-appended metal–organic frameworks’ by Bess Vlaisavljevich et al., Chem. Sci., 2015, 6, 5177–5185.

competing amine arrangements preset in experiment. This was outside the scope of our work. Once more, these calculations are perhaps now outdated given work in the eld in recent years. We again refer interested readers to a more recent study by Lee et al. 1 Fig. 1 Plot of the original chain model DE + ZPE in kJ mol À1 in comparison with the corrected numbers for the same model. Also included is our previously unpublished "alternative chain model" and data from Lee et al. 1 who employed the vdW-DF2 functional. Note that Lee et al. use 6 mmen-amines (1,1-dimethylenamine) per unit cell and the intermolecular interactions of amines across the ab-plane are treated more accurately due to a more extensive study with emphasis on understanding the role of these interactions. 1 Additionally, Ni was not computed since it was shown to engage in single site adsorption and not chain formation shortly after the publication of the original work.

Extended computational details to ensure reproducibility
In the course of rectifying the error in our calculations, we wanted to ensure that all revised calculations were converged using the exact same protocol; therefore, we repeated the PBE calculations for the pair and chain models using updated computational details given here to ensure reproducibility.
The M 2 (dobpdc) MOF contains six unsaturated metal sites per unit cell. To calculate the binding energies of CO 2 in its amine appended analogue mmen-M 2 (dobpdc), one mmen ligand per CO 2 was added per unit cell. The smaller sized ethylenediamine (en) was used to saturate the remaining amines not involved in CO 2 binding. In the case of the pair mode, two mmen-amines are included per unit cell only. All DFT calculations were performed with periodic boundary conditions carried out using the VASP 5.4.4 package (original calculations were performed with VASP 5.3.3). The PBE functional was employed to examine the energetics of CO 2 adsorption. 3 On-site Hubbard U corrections were employed for metal d electrons. 4 The U values are determined to reproduce oxidation energies in the respective metal oxides and are given in the tables below. The electron-ion interactions in these calculations were described with the projector augmented wave (PAW) method developed by Blöchl with an energy cutoff of 550 eV. 5 This combination of the PBE functional, PAW scheme, and energy cutoff was used for full geometry optimization of the various species investigated until the forces on all atoms were smaller than 0.02 eVÅ À1 and the SCF convergence was set to 1 Â 10 À7 eV. Given the large size of the unit cell and the tests with other numbers of K-points from the original study, only results obtained from G-point calculations are reported here. Finally, heats of adsorption are now reported below along with E + ZPE values, while in the original manuscript only E + ZPE were reported. No changes were made to how the vibrational corrections were computed; however, we have included some additional details to ensure reproducibility. 6 Harmonic vibrational modes (u i ) were computed for CO 2 in the gas phase and its bound product state (amine-CO 2 -MOF complex). The framework itself was taken to be rigid and only the vibrational modes associated with the motion of the amine, the metal center, rst coordination sphere (oxygen atoms bound to the metal in the MOF backbone), and (if present) the bound CO 2 were computed. Since the harmonic approximation breaks down for low frequency modes, we replaced all modes less than 50 cm À1 with 50 cm À1 when computing the zero-point and thermal energies. The following standard harmonic expressions were used to compute the vibrational corrections: Zero-point vibrational energy (ZPE) is: For CO 2 in the gas phase, the thermal correction to the energy was taken to be: While for the bound product, the rotational and translational degrees of freedom of CO 2 have been converted to additional vibrational modes allowing one to compute the thermal correction simply as:

Values for the chain model
The chain model used in our original study included 1 mmen-and 5 en-amines. The values from the original paper are reported in Table 1.
When we repeat these calculations using the procedure described in Section 1, we obtain the values in Table 2.
In addition to the chain model described above (1 mmen-and 5 en-amines per unit cell), during our original study we performed calculations with another model that was not included in the manuscript since its values yielded results further from experiment. This model includes only 1 mmen-amine per unit cell (no other amines) and was used to test the assumption that the ve enamines are indeed spectators with respect to the metal dependence of the binding energy. We present the results from this model in Table 3.
In the original paper we noted that the energy and bond length trends are correlated and are consistent with the Irving-Williams series. This is no longer true for all metals under investigation, with Zn being an outlier. The results for Zn can be explained by more recent work. 1

Values for the pair model
The model used to compute the "pair" adsorption mechanisms included 2 mmen-amines and 0 en-amines. The values in the original paper are presented in Table 5.

Lattice model plots
The lattice models to generate adsorption isotherms for these systems were run at one temperature ($25 C) using four different input parameters. First the M06-L and PBE values from the original paper were used once more as it has been some time since we have run the lattice model. Then the model is repeated with the new set of values from PBE. If we compare Fig. 7 and 8, the order is preserved, but the iniction points are spaced a bit differently. This is due to the scaling factor being constant and is something we scaled for each of the different systems as well. The slope is also a bit different, but not more then we should expect for this simple lattice model. Furthermore, we only ever aimed to reproduce the step and the order of the metals. Any ner details cannot be expected to be obtained from this model. The exact values used to compute the isotherms are given in the tables below.
The Royal Society of Chemistry apologises for these errors and any consequent inconvenience to authors and readers.