Pore-in-Pore Engineering in a Covalent Organic Framework Membrane for Gas Separation
Hongwei Fan, Haoran Wang, Manhua Peng, Hong Meng, Alexander Mundstock, Alexander Knebel, Jürgen Caro
Abstract
High Resolution Image Download MS PowerPoint Slide Covalent organic framework (COF) membranes have emerged as a promising candidate for energy-efficient separations, but the angstrom-precision control of the channel size in the subnanometer region remains a challenge that has so far restricted their potential for gas separation. Herein, we report an ultramicropore-in-nanopore concept of engineering matreshka-like pore-channels inside a COF membrane. In this concept, α-cyclodextrin (α-CD) is in situ encapsulated during the interfacial polymerization which presumably results in a linear assembly (LA) of α-CDs in the 1D nanochannels of COF. The LA-α-CD-in-TpPa-1 membrane shows a high H 2 permeance (∼3000 GPU) together with an enhanced selectivity (>30) of H 2 over CO 2 and CH 4 due to the formation of fast and selective H 2 -transport pathways. The overall performance for H 2 /CO 2 and H 2 /CH 4 separation transcends the Robeson upper bounds and ranks among the most powerful H 2 -selective membranes. The versatility of this strategy is demonstrated by synthesizing different types of LA-α-CD-in-COF membranes.