Self-supporting covalent organic framework membranes synthesized through two different processes: solvothermal annealing and solvent vapor annealing

Abstract

Rigid, freestanding covalent organic framework (COF-1) membranes have been synthesized from 1,4-benzenediboronic acid (BDBA) precursors using two different approaches: room temperature solvent-vapour annealing (SVA) and solvothermal annealing (SA). Characterization of films using Fourier-transform infrared (FTIR) spectroscopy, x-ray diffraction (XRD), and various microscopies shows that the films obtained through the two different routes vary in their retained BDBA proportion, crystal size and macroscale morphology. Gas adsorption measurements give specific surface areas of 579 ± 7 m2 g−1 and 739 ± 11 m2 g−1 respectively, suggesting that the average porosity of these films is competitive with bulk-synthesized COF-1 particles. The films have a stratified structure, with a dense, thin top layer and a thicker, sponge-like base layer. Using nanoindentation, we measured the Young’s modulus at the top surface of the SVA and SA films to be 3.64 ± 1.20 GPa and 3.33 ± 0.12 GPa respectively, with the smaller uncertainty for the SA film attributed to a more uniform morphology. These measurements provide useful experimental data pertaining to COF-1 mechanical properties, furnishing information relevant to the use of these free-standing membranes in applications such as gas filtration or storage.

A covalent organic framework membrane with enhanced directional ion nanochannels for efficient hydroxide conduction

“…[22][23][24][25][26][27] Meanwhile, the ordered 1D channels, well-aligned layer-sheet structure, high thermal/chemical stabilities, and readily customized functionalities make 2D COFs a promising candidate for the fabrication of new-generation membrane materials. [28][29][30] Furthermore, 2D COFs are ideal ionic conductive materials, which can realize continuous ion transport active sites and ultrafast ion conduction by enriching ordered in-plane nanopores. 31 In 2016, Jiang's group immobilized imidazole molecules into 1D open channels of TPB-DMTP-COF to prepare an ionic conductive COF.…”

Strength Enhancement of Polyurethane Film by Solution Annealing

“…The mismatch supramolecular interaction formed between rigid and flexible supramolecular fragments is used to realize the toughness of thermoplastic elastomers and thus improve their mechanical properties, but the synthesized elastomers become yellow due to the introduction of aromatic structure . So it can be concluded that the properties of polyurethane membranes can be improved by controlling several factors, such as intermolecular hydrogen bonds, molecular cross-linking structure, molecular weight, molecular structure symmetry, and so on. − …”

Structural Characteristics and Environmental Applications of Covalent Organic Frameworks

“…As adsorbents, COF pores attract and trap pollutants based on their affinity towards functional COFs. COFs are also touted as excellent robust materials to fabricate separation membranes [48,49]. In the membrane form, pollutants are separated based on diffusion rates relying on the size, geometry, or charge of permeate and retentate.…”