Spatially Confined π‐Complexation within Pore‐Space‐Partitioned Metal–Organic Frameworks for Enhanced Light Hydrocarbon Separation and Purification

Abstract Ultramicroporous metal–organic frameworks (MOFs) are demonstrated to be advantageous for the separation and purification of light hydrocarbons such as C 2 H 2 , C 2 H 4 , and CH 4 . The introduction of transition metal sites with strong π‐complexation affinity into MOFs is more effective than other adsorption sites for the selective adsorption of π‐electron‐rich unsaturated hydrocarbon gases from their mixtures. However, lower coordination numbers make it challenging to produce robust MOFs directly utilizing metal ions with π‐coordination activity, such as Cu + , Ag + , and Pd 2+ . Herein, a series of novel π‐complexing MOFs (SNNU‐33s) with a pore size of 4.6 Å are precisely constructed by cleverly introducing symmetrically matched C 3 ‐type [Cu(pyz) 3 ] (pyz = pyrazine) coordinated fragments into 1D hexagonal channels of MIL‐88 prototype frameworks. Benifit from the spatial confinement combined with π‐complex‐active Cu + of [Cu(pyz) 3 ], pore‐space‐partitioned SNNU‐33 MOFs all present excellent C 2 H 2 /CH 4 , C 2 H 4 /CH 4 , and CO 2 /CH 4 separation ability. Notably, the optimized SNNU‐33b adsorbent demonstrates top‐level IAST selectivity values for C 2 H 2 /CH 4 (597.4) and C 2 H 4 /CH 4 (69.8), as well as excellent breakthrough performance. Theoretical calculations further reveal that such benchmark light hydrocarbon separation and purification ability is mainly ascribed to the extra‐strong binding affinity between Cu + and π‐electron donor molecules via a spatially confined π‐complexation process.