The world’s oceans absorb a significant percentage of anthropogenic carbon emissions, and CO2 levels have profound effects on the marine environment. Of primary concern is the acidification of the oceans due to dissolved CO2. The goal of this research is to design new sensing technologies for deployment in the marine environment to detect CO2 pollutant. A series of carbon dioxide (CO2) receptors that are complexed to fluorene oligomers were studied computationally. In chapter 1, an overview of CO2 chemistry and various CO2 sensors is discussed. A short overview of the method (Kohn-Sham density functional theory and time-dependent density functional theory (TDDFT)) employed in this work is given. Chapter 2 presents a study on the interaction energy and electronic excitations of fluorene-receptors as CO2 sensors. The aim of this work is to gain an understanding of the nature of interactions between these receptors and CO2. The structural, electronic, and optical properties of these receptor complexes have been determined computationally. The monomer-receptor complexes show remarkable redshifts in their absorption spectra, which decrease on moving to dimer and trimer-receptor complexes (all blue-shifted).