This theoretical research article proposes an original conceptual framework the Three-Dimensional Operating Space (3DOS) model to interpret and predict the behaviour of nanomaterial-based catalysts in energy conversion and environmental remediation processes. Unlike conventional theoretical approaches that treat nanoscale effects as isolated phenomena, this study synthesizes spatial confinement, temporal dynamics, and energetic coupling into a unified analytical space, enabling the systematic mapping of catalyst performance drivers. The framework introduces novel theoretical constructs, including the "Dynamic Active Site Potential" and "Interdomain Synergy Coefficients," derived through logical conceptual synthesis and systems-level analysis. The central finding is that catalytic efficacy emerges non-linearly from the interaction between these three domains, generating performance regimes inaccessible to bulk materials. This conceptual research identifies predictive design principles, classifies nanocatalyst archetypes based on their 3DOS coordinates, and exposes critical gaps in current theoretical treatment of operando evolution. The manuscript contributes a new mental model for early-career researchers, bridging condensed matter physics, interfacial chemistry, and reaction engineering without mathematical formalism. The study is intentionally theoretical, analytical, and focused on conceptual advancement rather than literature compilation.