Morphology-dependent third-order optical nonlinearity of a 2D Co-based metal-organic framework with a porphyrinic skeleton

A two-dimensional (2D) Co-based metal-organic framework (MOF) with porphyrinic skeleton forms crystalline plates, flower-shaped clusters, and ultrathin films under optimized conditions, including the use of polyvinylpyrrolidone (PVP) as a surfactant. Ultrathin films demonstrate the best solution-based third-order nonlinear optical properties, featuring a nonlinear transmittance ( T ) value of 0.54, absorption coefficient ( α 2 ) of 9.5 × 10 −10 m W −1 and second hyperpolarizability ( γ ) value of 1.37 × 10 −28 esu, which are slightly better than those of the flower-shaped clusters ( T = 0.65, α 2 = 7.0 × 10 −10 m W −1 ; γ = 1.27 × 10 −28 esu), but marginally better than those of the crystalline thin plates ( T = 0.94, α 2 = 2.4 × 10 −10 m W −1 ; γ = 0.24 × 10 −28 esu). A two-dimensional (2D) Co-based metal-organic framework (MOF) with a porphyrinic skeleton forms crystalline plates, flower-shaped clusters, and ultrathin films under optimized conditions and these forms give distinctively different nonlinear optical properties.