Direct X‐ray Observation of Trapped CO 2 in a Predesigned Porphyrinic Metal–Organic Framework

Metal–organic frameworks (MOFs) are emerging microporous materials that are promising for capture and sequestration of CO 2 due to their tailorable binding properties. However, it remains a grand challenge to pre‐design a MOF with a precise, multivalent binding environment at the molecular level to enhance CO 2 capture. Here, we report the design, synthesis, and direct X‐ray crystallographic observation of a porphyrinic MOF, UNLPF‐2, that contains CO 2 ‐specific single molecular traps. Assembled from an octatopic porphyrin ligand with [Co 2 (COO) 4 ] paddlewheel clusters, UNLPF‐2 provides an appropriate distance between the coordinatively unsaturated metal centers, which serve as the ideal binding sites for in situ generated CO 2 . The coordination of Co II in the porphyrin macrocycle is crucial and responsible for the formation of the required topology to trap CO 2 . By repeatedly releasing and recapturing CO 2 , UNLPL‐2 also exhibits recyclability.