Core-Shell and Yolk-Shell Covalent Organic Framework Nanostructures with Size-Selective Permeability

Many methods exist for the synthesis of covalent organic frameworks (COFs), but precise morphology control allowing the tailoring of core-shell and yolk-shell nanostructures has been elusive, mainly due to poor control of the reaction-diffusion processes. Herein, we propose the precise regulation of the COF generation and decomposition rates and their relationship with the diffusion rate of COF species during the synthesis, which enables a successful preparation of core-shell, yolk-shell, hollow-spherical, and multiple yolk-shell COF structures with tunable sizes ranging from 200 to 1,400 nm. Formed COF structures can serve as nanoreactors or nanocontainers, with the shell layer providing molecular-size selectivity determined by the nanopore size demonstrated here using Suzuki coupling reactions with phenylboronic acid, which produce a size-cutoff efficiency for halogenated aromatics approaching 100%. The precise morphology design and control of COF particles and hybrids may help enhance application efficiencies and provide access to new functionalities for COF materials.