Wide Temperature Sieving of n-Butene and iso-Butene by a Zinc-Based Coordination Network with Record Separation

Separating n-butene and iso-butene through adsorption represents a viable and energy-efficient strategy. However, developing porous adsorbents that can effectively discern the subtle differences between these isomers remains a significant challenge. This study demonstrates that a zinc-based coordination network (CALF-20) exhibits a slight pore expansion with increasing temperature, creating nanochannels that preferentially adsorb n-butene over iso-butene. This unique temperature-dependent dynamic behavior enables effective sieving of n-butene from iso-butene within the temperature range of 273 to 423 K, a phenomenon not previously observed. Notably, CALF-20 exhibits the highest n-butene adsorption capacity (2.62 mmol g⁻¹) and the highest selectivity ratio (14.7) among sieving materials reported to date for n-butene isomers. Modeling calculations show that dynamic factors play a significant role in achieving such high adsorption separation capabilities. At medium temperatures, the initial separation of n-butene and iso-butene is achievable, which may provide a foundation for the future design of adsorbents intended to achieve efficient separation of n-butene/iso-butene under comparable temperature conditions. In the future, the intricate structure dynamics and enhanced capacity for molecular recognition will offer a new pathway for developing advanced sieving materials.