Spatial nanoconfinement provides a powerful framework for understanding and engineering matter for sustainable technologies. In our work, we first developed a scalable and broadly applicable method for the high yield production of diverse monolayer nanosheets, establishing a versatile material platform for both fundamental study and practical translation. Building on this platform, we then investigated ion separation and transport in confined systems, showing that nanoscale confinement can regulate ionic behaviour in ways that enable selective ion sieving and energy related functions. We further extended this concept from transport control to materials synthesis by demonstrating that confined spaces can also serve as nanoreactors, where molecular assembly and polymerization are directed with high precision to produce robust and functional membrane materials. Together, these studies establish a coherent research pathway from scalable nanomaterial manufacturing, to mechanistic understanding of ion behaviour under confinement, to the rational synthesis of advanced materials within confined architectures, highlighting spatial nanoconfinement as both a fundamental scientific theme and a practical strategy for developing next generation sustainable technologies.