Reprogramming Porosity: The Synthetic Evolution of Pore Engineering in Metal-Organic Frameworks.

Metal-organic frameworks (MOFs) provide an exceptional platform for pore engineering due to their modularity, crystallinity, and diverse synthetic routes. Traditionally, porosity was controlled by linker length and metal node selection, but recent advances enable active reprogramming of pore environments through synthetic and postsynthetic modifications. This review highlights strategies to tune pore size, geometry, surface chemistry, and flexibility, including linker exchange and insertion, defect engineering, cluster metalation, and covalent or coordinative postsynthetic modifications. It also discusses the growth of functional species within existing pores. Emphasis is placed on mechanistic design rules that define how far such transformations can proceed while preserving long-range order. By unifying these approaches under synthetic pore reprogramming, the review outlines a framework for systematically modifying MOFs beyond their original structures. This enables access to properties and functions unattainable in pristine materials and lays the foundation for designing programmable porous materials with tailored performance.