In the past ten years, two-dimensional porous materials have been favored by scholars due to their designable porous structures, including covalent organic frameworks (COF), crystalline porous organic polymers, and so on. With excellent physical and chemical properties, high crystallinity and large surface area porosity, COF has shown great application potential and has been widely used in the fields of energy storage, catalysis, molecular storage, and water purification/desalination. However, synthetic COFs are usually powder materials rather than bulk materials, which largely limits their practical use.
Felix Zamora, Autonomous University of Madrid, et al. reported a process based on sol-gel transition, solvent exchange and supercritical CO2 drying to produce COF aerogels. The obtained COF aerogel block has extremely low density and high porosity. The COF aerogel maintains the micropores and mesopores that make up the COF, showing excellent absorption capacity and removal efficiency. The author also extended the process to the preparation of COF aerogel composites, paving the way for functionalized bulk COF-based aerogels. The research was published in "Angew" as a paper entitled "Macroscopic Ultralight Aerogel Monoliths of Imine-based Covalent Organic Frameworks".

Article highlights:
1. The author proposes a simple three-step method based on sol-gel transition, solvent exchange and supercritical CO2 drying to produce ultralight imino-based COF aerogels. The two-dimensional imine-based COF sheets are connected together to form a layered porous structure. The process is simple, economical, environmentally friendly, and has mild conditions, and does not require adhesives and/or high pressure.
2. The obtained COF aerogel block has extremely low density (about 0.02 g cm-3) and high porosity (about 99%), and is an elastic material under moderate strain (<25-35%). It becomes a plastic material under greater pressure. It exhibits excellent toluene absorption capacity (absorption rate of 32 g g -1) and removal efficiency (about 99%), and has good recyclability.
3. The author also synthesized COF aerogel/iron oxide nanoparticle composites with measurable conductivity and magnetism, thereby extending the three-step strategy to synthesize COF aerogel/nanomaterial composites with multiple functions . The versatility of this strategy will promote the production of various new COF aerogels and functional composite materials related to practical industrial applications.