Isoreticular Series of Two-Dimensional Covalent Organic Frameworks with the kgd Topology and Controllable Micropores

Two-dimensional (2D) covalent organic frame-works (COFs) possess designable pore architectures but limitedframework topologies. Until now, 2D COFs adopting thekgdtopology with ordered and rhombic pore geometry have rarelybeen reported. Here, an isoreticular series of 2D COFs with thekgdtopologyandcontrollableporesizeissynthesizedbyemploying aC6-symmetric aldehyde,i.e., hexa(4-formylphenyl)-benzene (HFPB), andC3-symmetric aminesi.e., tris(4-aminophenyl)amine (TAPA), tris(4-aminophenyl)trazine(TAPT), and 1,3,5-tris[4-amino(1,1-biphenyl-4-yl)]benzene(TABPB), as building units, referred to as HFPB-TAPA,HFPB-TAPT, and HFPB-TABPB, respectively. The microporedimension down to 6.7 A is achieved in HFPB-TAPA, which isamong the smallest pore size of reported 2D COFs. Impressively, both the in-plane network and stacking sequence of the 2D COFscan be clearly observed by low-dose electron microscopy. Integrating the uniquekgdtopology with small rhombic micropores, these2D COFs are endowed with both short molecular diffusion length and favorable host-guest interaction, exhibiting potential for drugdelivery with high loading and good release control of ibuprofen

Automated summary

This study synthesizes a series of 2D COFs with the kgd topology and controllable pore size, achieving one of the smallest reported pore sizes for 2D COFs at 6.7 A. The in-plane network and stacking sequence of these COFs can be clearly observed by low-dose electron microscopy. With the unique combination of kgd topology and small rhombic micropores, these 2D COFs exhibit potential for drug delivery with high loading and good release control of ibuprofen.