Asymmetrical Exchange of Monomers for Constructing Hollow Nanoparticles and Antifragile Monoliths

Constructing nanoparticles (NPs) with spatial organization of complex components and precisely defined structures in a scalable yet simplistic way is critical for advancing many applications. Here we report a nanoscale Kirkendall-like conversion of covalent organic frameworks (COFs) via asymmetrical monomer exchange (AME) for precise architecture of hollow NPs. Easy manipulation of feeding strategies by adding one or more monomers simultaneously or sequentially can regulate AME and produce hollow NPs possessing single or multiple COF components with controlled spatial distributions. The NPs can be used as "cells" to construct centimeter-sized monolithic materials with Young's modulus of 263 MPa, compressive strength of 45 MPa, and elastic deformations over 20% via cold molding. The monolith shows antifragility that can be remolded after crushing and grinding into powders five times with the modulus little changed. Such an AME method provides precise yet convenient pathways for building organic nanoarchitectures and macroscopic materials that are otherwise inaccessible.