Molecular chemical engineering in chemical process design: From molecular mechanisms to process systems

The core of chemical process design lies in establishing cross-scale linkages between molecular mechanisms and macroscopic systems. This review introduces the multiscale framework of molecular chemical engineering, encompassing the “molecule-unit-system” hierarchy. On the molecular level, quantum chemical calculations, molecular simulations, and structure-property prediction enable accurate characterization of molecular structures and properties, thereby guiding the optimization of reactions and separations. Moving to the unit level, molecular insights are translated into phase equilibrium, kinetics, and transport models, supporting applications in complex separations and green solvent design. Process integration, simulation, and system-level sustainability assessment provide pathways for green and low-carbon design. Advances in multiscale modeling, artificial intelligence, and data-driven approaches have accelerated precision, intelligence, and greenness, though challenges remain in cross-scale fidelity and model interpretability. This review guides the design of complex chemical processes toward innovation and sustainability.