Macroporous Crystals: Design Principles, Synthesis Strategies, and Emerging Applications

Macroporous crystals—crystalline materials containing interconnected pores larger than 50 nm—have emerged as a distinct class of porous solids capable of overcoming the mass-transport limitations inherent to microporous and mesoporous frameworks. While smaller-pored crystalline materials dominate applications in catalysis, separations, and energy conversion, their narrow channels often restrict diffusion, limit accessibility to large guest species, and accelerate deactivation. Recent advances in colloidal templating, phase separation, additive manufacturing, and reconstruction-based synthesis now enable the formation of macroporous crystalline architectures with pore sizes extending from the sub-micrometer to micrometer scale while retaining long-range structural order. This review systematically examines pore-size classifications, synthesis strategies, structural characteristics, and structure–property relationships governing macroporous crystals, with emphasis on how true macroporosity enables near-bulk transport, enhanced optical functionality, and biological accessibility. Key applications in catalysis, photonics, energy systems, and biomedicine are discussed, alongside challenges related to crystallinity preservation, mechanical robustness, and scalable fabrication. Finally, a case study demonstrating a crystalline material with pores approaching 1 µm illustrates the feasibility of achieving unprecedented pore dimensions without relying on conventional templating approaches. By framing macroporous crystals as a distinct materials regime, this review provides design principles and perspectives to guide the development of next-generation crystalline porous materials.