Covalent organic framework membranes through a mixed-dimensional assembly for molecular separations

Abstract

Covalent organic frameworks (COFs) hold great promise in molecular separations owing to their robust, ordered and tunable porous network structures. Currently, the pore size of COFs is usually much larger than most small molecules. Meanwhile, the weak interlamellar interaction between COF nanosheets impedes the preparation of defect-free membranes. Herein, we report a series of COF membranes through a mixed-dimensional assembly of 2D COF nanosheets and 1D cellulose nanofibers (CNFs). The pore size of 0.45–1.0 nm is acquired from the sheltering effect of CNFs, rendering membranes precise molecular sieving ability, besides the multiple interactions between COFs and CNFs elevate membrane stability. Accordingly, the membranes exhibit a flux of 8.53 kg m −2 h −1 with a separation factor of 3876 for n-butanol dehydration, and high permeance of 42.8 L m −2 h −1 bar −1 with a rejection of 96.8% for Na 2 SO 4 removal. Our mixed-dimensional design may inspire the fabrication and application of COF membranes.

Emerging Functional Porous Polymeric and Carbonaceous Materials for Environmental Treatment and Energy Storage

“…[255] To promote the sieving effects and mechanical strength of COF membranes, 1D cellulose nanofibers (CNFs) were integrated into the membrane (Figure 12c). [247] The pore size (0.45-1.0 nm) that rendered membrane precise molecular sieving ability was obtained. Owing to the hydrogen-bonded parallel chains and abundant hydroxyl groups, the nanocomposites exhibited elevated membrane stability.…”

Design, Synthesis and Characterization of Nickel‐Functionalized Covalent Organic Framework NiCl@RIO‐12 for Heterogeneous Suzuki–Miyaura Catalysis

“…However, since Yaghi's landmark paper in 2005, research in this field had been mainly focused on the design and synthesis of new COF structures intending to increase the surface area and pore volume . For this reason, more recent studies concerning COF applications have become an active area of research in organic chemistry …”

Laminated self-standing covalent organic framework membrane with uniformly distributed subnanopores for ionic and molecular sieving

“…However, as far as size-dependent separation with COF membrane is concerned, it has been proved to be very difficult to accurately control the pore sizes in the sub-nm scale, either through control of monomer size or through pore modification [6][7][8] . Recently, Yang et al 35 reported several COF membranes with sub-nm pores prepared by vacuum filtration using 2D COF nanosheets and 1D cellulose nanofibers (CNFs) as starting materials. Due to the shielding effect of CNFs, the aperture of obtained COF-based membrane is in the range of 0.45-1.0 nm.…”