posted on 2022-04-04, 18:47authored byLiuxiao Li, Qinbai Yun, Chongzhi Zhu, Guan Sheng, Jun Guo, Bo Chen, Meiting Zhao, Zhicheng Zhang, Zhuangchai Lai, Xiao Zhang, Yongwu Peng, Yihan Zhu, Hua Zhang
Two-dimensional
(2D) covalent organic frameworks (COFs) possess
designable pore architectures but limited framework topologies. Until
now, 2D COFs adopting the kgd topology with ordered and
rhombic pore geometry have rarely been reported. Here, an isoreticular
series of 2D COFs with the kgd topology and controllable
pore size is synthesized by employing a C6-symmetric aldehyde, i.e., hexa(4-formylphenyl)benzene
(HFPB), and C3-symmetric amines i.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 micropore dimension down
to 6.7 Å is achieved in HFPB–TAPA, which is among the
smallest pore size of reported 2D COFs. Impressively, both the in-plane
network and stacking sequence of the 2D COFs can be clearly observed
by low-dose electron microscopy. Integrating the unique kgd topology with small rhombic micropores, these 2D COFs are endowed
with both short molecular diffusion length and favorable host–guest
interaction, exhibiting potential for drug delivery with high loading
and good release control of ibuprofen.