Temperature-Induced Defects for Enhanced Optical Limiting in a Wide-Band-Gap Dual-Linker Framework

Abstract

The escalating demand in optical limiting applications necessitates the exploration of novel platforms with tunable optical properties, among which metal–organic frameworks are emerging as a viable candidate. ZIF-62, a dual-linker framework that is not widely researched, exhibits an orthorhombic phase with imidazole and benzimidazole as its linkers and zinc as the metal cation. This article concentrates on the influence of the synthesis temperature on the optical limiting response of ZIF-62. ZIF-62 is found to be a material with a wide band gap that can be used as an optical limiter to protect human eyes and sensors. The defects in the crystal lattice, confirmed by X-ray diffraction (XRD) analysis, act as localized electronic perturbations and boost their absorption properties. Increasing the synthesis temperature from 80 to 130 °C induces a red shift in the band gap. Photoluminescence properties show a magenta emission when the excitation was kept at 275 nm for the sample synthesized at 130 °C and a decrease in the emission for the sample synthesized at 80 °C. Similar to the linear absorption studies, the nonlinear absorption studies reveal an increase in the β value to be 1.07 × 10^–10 m/W and a reduction in the optical limiting threshold of 3.61 × 10¹² W/m² for the sample synthesized at 130 °C. In summary, the temperature-dependent optical properties of ZIF-62 and their impact in optical limiting applications are reported for the first time.