Due to the advantages of the high surface area and high porosity, Metal-Organic Framework (MOF) materials are widely used in gas storage. As a typical MOF material, Zeolitic Imidazolate Framework-8 (Zif-8) has high selectivity and adsorption capability of carbon dioxide (CO2). In this thesis, we investigated the infrared absorption of CO2 at the 2.0 m window using a lab-built optical spectroscopic system consisting of a broadband super-continuum light source, a monochromator, and a high-gain IR photodetector. In order to reduce the common-mode noise from the light source, we wrote a LabVIEW program to synchronize the data collected from the sampling and reference channel to minimize the effect of intensity fluctuation. Based on our experimental results, we obtained the vibrational-band IR absorption spectra of CO2 in ZIF-8, which is similar to that from the gas cell. However, the IR enhancement factor is abnormally large and cannot be solely attributed to the CO2 adsorption concentration by MOF. In parallel, we tested a MOF coated multi-mode fiber sensor to study the property of CO2/N2 selectivity of MOF, showing a non-linear relationship between the IR absorption and CO2 concentration. Therefore, we conclude that MOF has an extraordinary capability to enhance the IR gas sensitivity, but requires further investigation to understand the physics mechanism.