Gas Sorption Properties of Isostructural Co‐MOFs Containing Dipyridylporphyrin Linkers with Different Substituents at the 10,20‐ meso ‐Positions

Two new isostructural 3D dipyridylporphyrin‐based MOFs, [Co(DpyDClP)] 6 · 18H 2 O ( I ) and [Co(DpyDCNP)] 6 · 18H 2 O ( II ), were prepared and structurally characterized by X‐ray crystallography [DpyDClP: 5,15‐di(4‐pyridyl)‐10,20‐di(4‐chlorophenyl)porphyrin; DpyDCNP: 5,15‐di(4‐pyridyl)‐10,20‐di(4‐cyanophenyl)porphyrin]. They display exactly the same framework structures, notwithstanding different substituents at the 10,20‐ meso ‐positions of the dipyridylporphyrin backbones. Both substituents, –Cl for I and –CN for II , are completely exposed to the open space of solvent‐free I and II . Therefore, the two MOFs have the same framework structures with distinct pore functionalities. Solvent‐free I and II have solvent‐accessible void volumes of 17.3 and 14.9 %, respectively. The thermal properties of I and II are very similar, but the gas sorption properties strongly depend on the pore dimensions and functionalities. Compound I has a higher uptake of CO 2 compared with that of II due to its larger void volume. Particularly, CO 2 sorption isotherms at 196 K indicate dramatically different patterns depending on the meso ‐substituents. Whereas I shows S‐shape isotherms for CO 2 adsorption/desorption at 196 K, II does not. The sorption of N 2 , H 2 , and CH 4 by the two MOFs was also investigated.