Towards high-performance nonlinear optical materials through embedding a D–A system into β-ketoenamine-linked COFs

Abstract

Two covalent organic framework (COF) films supported by a glass substrate were obtained by solvothermal reaction of an electron donor with electron acceptor 1,3,5-triformylbenzene (TF) or 2,4,6-triformylphloroglucinol (TFP), respectively. The TFP-BD film exhibits a nonlinear absorption coefficient of −3.01 × 10⁵ cm GW⁻¹. The TFP-BD film can aggregate electrons around the connected monomer through the D–A effect due to its highly polar and electronegative carbonyl oxygen atoms, thereby modulating the electronic structure of the COFs. This work provides a novel approach for the structural modulation of optical materials with strong nonlinearity.