Electrostatically Driven Selective Adsorption of Carbon Dioxide over Acetylene in an Ultramicroporous Material

Separating acetylene from carbon dioxide is important but highly challenging owing to their similar physical properties and molecular dimensions. Herein, we report highly efficient electrostatically driven CO 2 /C 2 H 2 separation in an ultramicroporous cadmium nitroprusside ( Cd‐NP ) with compact pore space and complementary electrostatic potential well fitting for CO 2 , thus enabling molecular quadrupole moment recognition of CO 2 over C 2 H 2 . This material shows a high CO 2 /C 2 H 2 uptake ratio of 6.0 as well as remarkable CO 2 /C 2 H 2 selectivity of 85 under ambient conditions with modest CO 2 heat of adsorption. Neutron powder diffraction experiments and molecular simulations revealed that the electrostatic potential compatibility between pore structure and CO 2 allows it to be trapped in a head‐on orientation towards the Cd center, whereas the diffusion of C 2 H 2 is electrostatically forbidden. Dynamic breakthrough experiments have validated the separation performance of this compound for CO 2 /C 2 H 2 separation.