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Covalent organic frameworks (COFs) demonstrate considerable promise for gas and chemical sensing applications. Although there has been notable advancement in synthesizing such crystalline materials, the utilization of template-free approaches to fabricate COFs with flower-like microstructures remains infrequent. Herein, we report the synthesis of microflower-like and hollow microtubular phenylpyridine-based COFs─TAPP-TFBZ and TAPP-TFBP COFs─through template-free 4 + 4 polycondensation of 5′-(2,6-bis(4-aminophenyl)pyridin-4-yl)-1,1′:3′,1″-terphenyl-4,4″-diamine (TAPP-4NH2) with 4′,5′-bis(4-formylphenyl)-1,1′:2′,1″-terphenyl-4,4″-dicarbaldehyde (TFBZ-4CHO) and 5′,5″-bis(4-formylphenyl)-1,1′:3′,1″:3″,1‴-quaterphenyl-4,4‴-dicarbaldehyde (TFBP-4CHO), respectively. The resultant COFs exhibit exceptional thermal stability beyond 592 °C and possess high Brunauer–Emmett–Teller (BET) surface areas surpassing 943 m2 g–1. The TAPP-TFBZ COF has a dual porosity feature, whereas the TAPP-TFBP COF demonstrates a singular porosity. Interestingly, the TAPP-TFBZ COF microflowers have promising capabilities as a prospective fluorescent chemosensor, enabling the sensitive and selective sensing of H2S. Our developed sensing assay demonstrates a time efficiency of 10 min for completion while achieving a limit of detection of 1.6 nM. This work will advance research into the design concepts of flower-shaped COF materials that hold potential for applications in gas and chemical sensing.
Chen et al. (Thu,) studied this question.