Research on the Synthesis and Application of Photo Controlled Intelligent Porphyrin - based Covalent Organic Frameworks Linked by Azobenzene

This study synthesizes a photo controlled intelligent covalent organic framework (AZO-TBPP-COF) using photoisomeric small molecule p -aminoazobenzene as a linker and meso-tetra (p-bromophenyl) porphyrin (TBPP) as monomer via Buchwald Hartwig coupling reaction. AZO-TBPP-COF has improved the light absorption range and band gap compared with TBPP, which enable AZO-TBPP-COF has a more negative band gap to achieve great potential in photocatalytic degradation of organic pollutants and reduction of heavy metal ions. The adsorption of AZO-TBPP-COF towards organic dyes and heavy metal pollutants showed significant differences before and after structural torsion irritated by light irradiation. After UV irradiation, the dark adsorption rate of methylene blue by cis AZO-TBPP-COF increased by nearly 2.6 times. The cis-trans isomerization of azobenzene under visible light causes changes in the microstructure of AZO-TBPP-COF, directly affecting the zeta potential and adsorption capacity. And the increased zeta potential of COF after structural inversion, reduces the electrostatic repulsion towards positively charged organic dyes. Meanwhile, stable trans AZO-TBPP-COF exhibits excellent photocatalytic performance against organic dyes and heavy metal ions in the visible light range compared to TBPP. Therefore, the adsorption and photocatalytic abilities of light regulated AZO-TBPP-COF highlight the important applications of intelligent porous organic materials in internal ion transport, energy conversion, and environmental remediation.