Vertically aligned carbon nanotube (VACNT) arrays with hierarchical and anisotropic morphology effectively extend the intrinsic extraordinary nanoscale properties (mechanical, electrical, and thermal) of individual nanotubes to the macroscale and in an accumulative manner. Thus, VACNTs hold promise to transform a diverse set of practical applications that will ultimately enable enhanced sustainability. I will first discuss the opportunities and challenges to incorporate VACNTs into environmental and energy-engineering sectors. Further, I will present our explorations on fabrication of conformal-coating VACNT/manganese oxide (MnOx) hybrids via atomic layer deposition (ALD) and their potential applications in energy and environmental-related fields. Providing high electrolyte accessibility via well-defined intertube space and exceptionally conductive support, VACNTs were found to compensate the poor electrical conductivity and low surface area shortcomings of MnOx, resulting in a hybrid material that exhibited simultaneously high mass specific (220 F/g) and area specific (1.15 F/cm2) capacitance. This outstanding capacitance positions them as candidate materials for energy storage devices and also exhibits promise for remarkable salt adsorption capacity (27.5 mg NaCl /g material) to enable water desalination via capacitive deionization (CDI).