The syntheses of the flexible TAPDA-based covalent organic frameworks utilized for capturing iodine and fluorescence sensing 2,4-dinitrophenol.

The hexa(4-formyl-phenoxy)cyclotriphosphazene (NOP-6--CHO) and 2,4,6-tris(4-formylphenoxy)-1,3,5-triazine (TPT-3-CHO) are common knots of the flexible covalent organic frameworks (COFs), which may undergo Schiff base reaction with diamide and ternary amine, but with no examples of quaternary amine. Herein, we chose quaternary amine -- N,N,N',N'-tetrakis(4-aminophenyl)-1,4-phenylenediamine (TAPDA) to react with NOP-6-CHO and TPT-3-CHO to synthesize flexible TAPDA-based COFs (HTAPDA and TTAPDA) for the first time. The flexible TAPDA-based COFs have flexible units and 3D triangular or 2D hexagonal pores which make the pores nimble and self-adaptable abilities. Delightly, the flexible TAPDA-based COFs have the high BET-specific surface areas of 1103 and 1048 m2/g and show some crystallization and high thermal stability. They can adsorp I2 in both the gaseous phases (4.08 and 3.80 g g-1 at 77 K) and the solution. The flexible TAPDA-based COFs possess excellent fluorescent properties whether at dispersion or solid states and may be used for fluorescent sensing 2,4-dinitrophenol (DNP) with high selectivity and sensitivity (KSV: 2.49 × 104 and 2.36 × 104 L mol-1). Fluorescence quenching of the flexible TAPDA-based COFs is observed upon coaction of photo-induced electron transfer process and fluorescence resonance energy transfer process.