Covalent organic frameworks (COFs) represent an emerging class of porous crystalline materials composed of light elements. Typically C, N, O, and/or B crystallize into two-dimensional (2D) layered structures or three-dimensional (3D) networks. The nearly eclipsed structures of most 2D COFs give rise to high intrinsic charge mobilities and their recent synthesis as oriented thin films portends their use in optoelectronic and energy-storage devices. In contrast, few 3D COFs have been crystallized, and despite exhibiting exceptionally high surface areas (> 4000 m²g^–1) and record low densities (0.17 gcm^–3), these networks have no well-developed applications.

 
David N. Bunck and William R. Dichtel, Cornell University, NY, USA, have demonstrated a modular and versatile strategy to functionalize the interior of 3D COFs by cocondensing tetrahedral and truncated, trigonal monomers. The functionalized materials tolerate high loading levels of the truncated building blocks while retaining the crystallinity and high surface area of the parent 3D COFs.
The reseachers are currently expanding the generality of this approach to other COF linking chemistries and developing these materials for applications in catalysis and payload release.

• Internal Functionalization of Three-Dimensional Covalent Organic Frameworks,
  David N. Bunck, William R. Dichtel,
  Angew. Chem. Int. Ed. 2012, 51.
  DOI: 10.1002/anie.201108462