Figure 4.

Selected views of the 100 K single-crystal X-ray diffraction structure of CO₂-inserted (±)-dach–Zn₂(dobpdc) depicted in space group P3₁21 (right-handed framework pores). Light-blue, blue, red, gray, and white spheres represent Zn, N, O, C, and H atoms, respectively. (a) Pore view. Hydrogen bonds between ammonium carbamate chains in the ab plane are enabled by framework contraction. Both (R,R)-and (S,S)-dach were resolved in the structure, but for clarity, only (R,R)-dach is shown. (b) Conformations of (R,R)-and (S,S)-dach ammonium carbamates, which were both resolved in the structure. The carbamate carbon, nitrogen, and oxygen atoms and the ammonium nitrogen of (R,R)- and (S,S)-dach were exactly superimposed in the structure. (c) View of the ammonium carbamate chains along the c axis of the material. For clarity, only (R,R)-dach is shown. (d) View of hydrogen bonding between neighboring ammonium carbamate chains in the ab plane. Hydrogen bonding within the chains along the c axis is also visible. For clarity, only (R,R)-dach is shown.