Development of multi-channel nanofibrous molecular sieves with aerogel structure for efficient carbon dioxide capture

Abstract

Polymers of intrinsic microporosity (PIM)-based solid adsorbents hold great promise for CO₂ adsorption and separation, owing to its abundant microporous pores and theoretically high specific surface area. However, PIM-based solid adsorbents encountered limitation in practical applications due to their singular micropore structure and inadequate mechanical properties. Therefore, there is an urgent need to develop PIM-based porous solid adsorbents with flexibility, durability and excellent adsorption ability. Here, the aerogel-structured nanofibrous molecular sieves composed of amidoxime modified polymers of intrinsic microporosity (AO-PIM-1), have been successfully fabricated by electrospinning via non-solvent-induced phase separation. The obtained AO-PIM-1 nanofibrous molecular sieves were crosslinked through in situ spraying with an epoxy-based monomer to improve their structural stability. How different polymer molecular weight influences the pore structure, porosity and specific surface area of the nanofibrous molecular sieves has been further investigated. Interestingly, this successful construction introduced a hierarchical porous structure in a series of AO-PIM-1 nanofibrous molecular sieves prepared with different molecular weight. This structure serves as a continuous channel for transporting CO₂ molecules, thus facilitating the adsorption capacity. In addition to exhibiting the most uniform porous structure, the AO-PIM-1-A1 nanofibrous molecular sieve (with a weight-average molecular weight near to 47 kDa) exhibited an enhanced mechanical property (2.2 MPa), high specific surface area (445 m²/g) and excellent CO₂ adsorption performance (15.02 % improvement over its powder form). This work will inspire the design and development of high performance porous fibrous adsorbents, not only for the CO₂ adsorption but also for other adsorption applications.