Superb Nonlinear Absorption of Triphenylene‐Based Metal–Organic Frameworks Associated with Abundant Metal d Electrons
Yanhui Sun, Hui Li, Xiangyun Gao, Zhiyang Yu, Zhipeng Huang, Chi Zhang
Abstract
Abstract The exploitation of high‐performance nonlinear optical (NLO) materials is necessitated by the broad application of ultra‐intensive and ultra‐fast lasers. The superb nonlinear absorption and electronic‐structure‐related NLO response of M 3 HHTP 2 are introduced here, where M is Co(II), Ni(II), or Cu(II) and HHTP is 2,3,6,7,10,11‐hexahydroxytriphenylene. With the laser excitation at 532 nm, the Cu 3 HHTP 2 exhibits a two‐photon absorption (2PA) cross‐section of 1.38 ± 0.11 × 10 7 GM, a value much larger than those of most reported NLO materials so far. The NLO response of M 3 HHTP 2 correlates strongly with the number of metal d electrons. With metal d electrons number increasing from 7 to 10, the optical nonlinearity of M 3 HHTP 2 under the laser excitation at 532 nm varies from three‐photon absorption (3PA) in Co 3 HHTP 2 , a combination of 3PA and 2PA in Ni 3 HHTP 2 , to 2PA in Cu 3 HHTP 2 . Abundant metal d electrons can mitigate the ground‐state depletion, and therefore the 2PA is enhanced. Accordingly, the superb nonlinear absorption of Cu 3 HHTP 2 can be associated with abundant d electrons in Cu.