Hierarchically Porous Multivariate COF Aerogel With Enhanced Diffusibility and Tailored Functionality for Highly Efficient Bromine Sequestration

Abstract

Elemental bromine, owing to its inherently toxic, corrosive, and volatile nature, poses a great threat to the environment and public health. In this regard, although crystalline covalent organic frameworks (COFs) offer ordered porosity and tunable functionality, their powdered form often leads to aggregation, limited diffusibility, and poor processability. Transforming COFs into ultralight, mechanically robust, and easily processable aerogels overcomes these challenges by introducing hierarchical porosity, reduced density, and rapid mass transport pathways. Herein, we have strategically fabricated a series of multivariate covalent organic frameworks in the form of aerogels with high surface area, hierarchical porosity, and multiple binding sites for efficient sequestration of bromine in both vapor and solution phases. The multivariate aerogel shows a high Br2 uptake capacity, ultrafast adsorption kinetics, excellent selectivity toward Br2, and outstanding performance under dynamic flow-through conditions, validating its practical applicability. Additionally, the aerogel can sequestrate bromine from aqueous solutions, reducing the concentration to below the permissible limit set by the WHO (< 10 ppm). This study demonstrates the potential of multivariate COF aerogels and establishes a fundamental strategy for designing task-specific systems through rational building-block modulation, offering a versatile pathway toward targeted environmental remediation and separation applications.