Third-order nonlinear optical susceptibility of (Cu, Mn, Cd) doping zeolitic imidazolate framework-67 in the visible region

A set of metal-organic frameworks (MOFs), pure ZIF-67 and doped with transient metal ions (Cu, Mn, and Cd), were synthesized from Co(II) nitrate and 2-methylimidazole and completely characterized. The MOFs synthesis proceeded through a facile one-step strategy based on the aqueous solution at room temperature. The physical characterization of fabricated MOFs by FT-IR, XRD, TEM, and SEM techniques revealed a nano-crystalline structure that undergoes a negligible variation upon inserting impurities of Cu, Mn, and Cd ions. Considering the XRD pattern, values of 5.9%, 14.78%, 16.02%, and 16.40% were resulted for the crystallinity index of ZIF-67, Cu-ZIF-7, Mn-ZIF-67, and Cd-ZIF-67, respectively. The E-g for pure ZIF-67 and ZIF-67 doped with cations of Cu, Mn, and Cd was measured to be similar to 3.22, 2.16, 1.96, and 1.95 eV, respectively. The nonlinear optical (NLO) features of synthesized samples were evaluated via the Z-scan method at 532 nm. The positive nonlinear refractive (NLR) index of samples demonstrated the self-defocusing effect. The nonlinear absorption coefficient (NLA) of samples dedicated to the two-photon absorption (TPA) effect. The crystallinity index, polarizability treatment, and the ionic radius of doped ions increase the NLO properties of ZIF-67.