Zn–N Dual-Site Activated Ultramicroporous Carbon Nanofibers for Kinetically Enhanced Ethylene/Ethane Separation

Adsorptive separation technology provides an environmentally friendly and feasible alternative to the energy-intensive cryogenic distillation traditionally used for ethylene/ethane separation. Although ultramicroporous carbon is considered a promising industrial adsorbent, it is limited by the slow diffusion of ethylene due to steric effects. Herein, we propose a strategy of zinc–nitrogen dual activation sites to construct diffusion channels within carbonaceous ultramicropores. Specifically, nitrogen-containing cross-linking agents are added to electrospun polyacrylonitrile fibers coordinated with zinc, and the degree of polymer chain cyclization is controlled to achieve a subangstrom level fine control of the pore of the derived carbon CPN-x. The gradient molecular probe method confirmed that CPN-1 has both a fast diffusion channel larger than 5 Å and a sieving ultramicropore between 3.7 and 4.1 Å, achieving an outstanding static uptake ratio, diffusion rate, and kinetic selectivity for ethylene/ethane. The significant separation performance of the dynamic breakthrough and the purity of desorbed ethylene further verify the industrial application potential of CPN-1. This work provides valuable guidance for regulating the structure of carbon-based adsorbents with multiple active sites to overcome the selectivity-kinetic trade-off effect in gas separation.