Trifluoromethyl-Functionalized 2D Covalent Organic Framework for High-Resolution Separation of Isomers

Abstract

Development of novel functional materials for effective isomer separation is of great significance in environmental science, chemical industry, and life science due to the different functions of isomers. However, the similar physicochemical properties of isomers make their separation greatly challenging. Here, we report the fabrication of trifluoromethyl-functionalized 2D covalent organic framework (COF) TpTFMB with 2,2′-bis(trifluoromethyl)benzidine (TFMB) and 1,3,5-triformylphloroglucinol (Tp) for the separation of isomers. TpTFMB was in situ-grown on the inner surface of a capillary for the high-resolution separation of isomers. The introduction of hydroxyl and trifluoromethyl functional groups with uniform distribution in 2D COFs is a powerful tactic to endow TpTFMB with various functions such as hydrogen bonding, dipole interaction, and steric effect. The prepared TpTFMB capillary column enabled the baseline separation of positional isomers such as ethylbenzene and xylene, chlorotoluene, carbon chain isomers such as butylbenzene and ethyl butanoate, and cis−trans isomers 1,3-dichloropropene. The hydrogen-bonding, dipole, and π−π interactions as well as the structure of COF significantly contribute to the isomer separation. This work provides a new strategy for designing functional 2D COFs for the efficient separation of isomers.

General Two-Step Method for the Fabrication of Covalent-Organic Framework-Bound Open-Tubular Capillary Columns for High-Resolution Gas Chromatography Separation of Isomers

“…In particular, EB and xylene isomers were baseline separated within 4.6 min with a high column efficiency (21,351–25,876 plates m –1 ) and good resolution ( R EB/ m x = 2.2, R m x/ p x = 1.6, and R p x/ o x = 3.1), which outperforms the reported 2D COF and other porous material-based GC stationary phases (Table S5). ,,,,,, …”

“…The introduction of suitable polar group into COFs can improve the separation performance of COF for isomers (such as C8 compounds). , Hydroxyl is a multifunctional polar group. − Although hydroxyl-based COF monomers are easy to obtain, hydroxyl-functionalized COF has not been explored as the stationary phase for GC. With this in mind, Tab-DHTA (DHTA can provide two hydroxyls) with a proper pore size (3.5 nm) and high crystallinity was used to demonstrate the two-step fabrication of COF-bound open-tubular capillary columns .…”

Tuning Topology of Two-Dimensional Trifluoromethyl-Functionalized Covalent Organic Framework for Efficient Separation of Isomers

“…The separation performance of the BTAPa-CF 3 -bound capillary column for the separation of xylene and chlorotoluene isomers was compared with other reported stationary phases. The BTAPa-CF 3 -bound capillary column showed shorter separation time or higher resolution than other reported stationary phases, such as MOF-CJ3, COF TpTFMB, COF BtaMth, and ZIF-8@PDMS for the separation of xylene isomers, and P6A-C10, COF TpTFMB, 2D-Zr-BTB-C 6 , and [ZnCl 2 L] 2 for the separation of chlorotoluene isomers. The above results demonstrate the good separation ability of the BTAPa-CF 3 -bound capillary column (see Tables S7 and S8).…”

“…Biphenyl-3,3′,5,5′-tetracarbaldehyde (BTA) and 1,3,5-benzenetricarboxaldehyde (Tb) with different symmetries are chosen as ligands to react with 2,5-diaminobenzotrifluoride (Pa-CF 3 ) for the synthesis of COFs BTAPa-CF 3 and TbPa-CF 3 with different topologies, respectively (Figure ). The trifluoromethyl functional group is introduced into the COFs to enhance the dipole force for the effective improvement of separation . Moreover, TbPa-CF 3 is designed with a pore size similar to that of the larger pore in BTAPa-CF 3 to show the role of the smaller pore in heteropore BTAPa-CF 3 in separation.…”

Tailoring Three-Dimensional Cross-Linked Networks Based on Water-Soluble Polymeric Materials for Stable Silicon Anode

“…We specifically explored the effectiveness of two functional groups: the trifluoromethyl group (−CF 3 ) and the ether linkage. The presence of the −CF 3 groups in the TFMB and TFODA molecules can enhance the polarity strength of the binder, , facilitating the formation of dynamic hydrogen bonds with the Si surface. These hydrogen bonds act as sacrificial bonds, capable of breaking to dissipate energy and then reforming during volume changes.…”