Specular (direct, unobstructed) transmittance was characterized with a double-beam spectrophotometer (Cary 5000, Agilent) in air. Diffuse reflectance and total transmittance of crystalline ZIF-62 powder and bulk agZIF-62 glass, respectively, were characterized using the same spectrometer equipped with an integration sphere (DRA 2500, Agilent). For diffuse reflection measurements, the powder sample was pressed into a glass sample holder with a cavity of 20 × 20 × 0.5 mm and flattened with a microscope glass slide to allow for vertical positioning of the sample as required by the device configuration. A Spectralon white standard was used as 100% diffuse reflectance reference. For total transmission measurements (accounting for directly transmitted and forward scattered light), the agZIF-62 glass was placed above the integration sphere opening for the incoming beam.