Energy is essential to human society to ensure our quality of life and to underpin all other elements of the economy. The world has reached a pivotal age of energy awareness due to accelerated consumption of conventional energy sources (fossil fuels, coal, natural gas, et al.). How to effectively reduce inefficient consumption of these natural sources, and in the meantime actively seek new innovative sustainable energy sources with minimized greenhouse effect are major research topics and have attracted wide spread efforts throughout the world. Ionic liquids (ILs) and deep eutectic solvents (DESs) as excellent alternative solvents are being proposed as promising liquid materials for applications, and have attracted significant attention in diverse industrial communities due to their multifaceted properties. Either used as electrolytes in electrochemical devices, or as adsorbents for CO2 capture, the functional performance of ILs and DESs is essentially determined by structural and dynamical properties of ion/molecular species in local environments, which are highly heterogeneous and are correlated with delicate interactions among ionic species, potential impurities, gas molecules, and their intrinsic interactions with charged boundaries (electrodes). Concerning the current research status of ILs and DESs, the traditional trial-and-error way to find appropriate ILs/DESs and to optimize their functional performance leads to huge cost on material synthesis and experimental characterizations. Additionally, a judicious selection of ions and molecules with desirable physicochemical properties to meet specific requirements remains terra incognita. Thus an economical pre-screening procedure should be established to determine essential structure-property relationship in representative systems. Molecular simulations, in close interplay with experiments, are well positioned to provide fundamental understanding of complicated phenomena on molecular level due to recent boosts of computer power and advent of smart computational algorithms. This is particularly useful for ILs and DESs because of their large diversities and complicated landscape of intermolecular interactions. This program involves computational studies of the development of hierarchical ionic models for ILs and DESs in bulk solution, in mixtures, and in confined environments. In an integrated multiscale modeling approach, extensive first-principle calculations (GAUSSIAN/CP2K) will be performed using highly accurate density functional theory with varied functional forms and orbital basis to predict particular interactions between ionic groups. Furthermore, extensive atomistic and coarse-grained simulations (GROMACS/LAMMPS) will be carried out to reveal essential factors governing delicate interactions between ion and molecular species, and essential solvent organizations in bulk region, to study the investigate detailed information of local ionic structures, molecular distributions and collective dynamical properties in confined environments. The microstructures and dynamics of ILs and DESs in liquid-solid regions (for battery research) and in liquid-gas interfaces (for gas absorption study) will be significantly investigated. Several important factors, including intrinsic ion and molecular structures (relative ionic sizes and shapes), potential impurities, solid surface types (inorganic or metal), surface roughness and chemical compositions (hydrophobic or hydrophilic), as well as the magnitude of applied single or combined external fields (flow or electrostatic fields), will be systematically considered in atomistic and mesoscale coarse-grained simulations.