CO2/CH4 separation using flexible microporous organic polymers with expansion/shrinkage transformations during adsorption/desorption processes

Abstract

• BOP-1 can separate CO 2 /CH 4 with a selectivity of 568 at 0.02 bar. • BOP-1 shows a expansion/shrinkage transformation for CO 2 adsorption/desorption. • The flexible –CH 2 –NH– linker contributes to the flexibility of BOP-1. CO 2 capture and biogas stream purification are of significance to minimize their effect on the global climate change. Usually, flexible metal-organic frameworks (MOFs) could show responsive adsorption for a specific guest. However, in this work, a flexible microporous organic polymer (MOP), BOP-1, was synthesized via intentionally selecting two functional groups (Cl and NH 2 moieties). Results show that BOP-1 has a higher uptake of CO 2 under 1 bar, i.e., 3.94 and 1.60 mmol/g at 273 and 298 K, respectively. Especially, at 273 K, BOP-1 shows an abrupt transformation over CO 2 adsorption and exhibits a high CO 2 /CH 4 selectivity of 568 at 0.02 bar. Both experimental and theoretical methods reveal that the flexible –CH 2 –NH– linker within the framework plays a critical role in dominating CO 2 binding and contributing the flexibility of host frameworks. Our findings could open a new possibility to tailor the function and flexibility of MOPs and to achieve their specific response to targets for the practical application in adsorption.