Programming High-Density Mesoporosity in Monodispersed MOF Single Crystals via Inherent Jahn-Teller Distortion

Incorporating high-density mesoporosity into single crystals has long posed a fundamental challenge, as traditional pore-engineering methods inevitably impair long-range crystalline order. Here, we repurpose an inherent crystallographic defect-the Jahn-Teller distortion (JTD)-as a programmable tool for encoding mesoporosity within monodisperse metal-organic framework (MOF) single crystals. As proof of concept, by incorporating metastable Mn³⁺ ions and regulating their releasing from lattice through simple kinetic levers (time and temperature), we can directly "write" an interconnected mesopore network with tunable pore size of 5-30 nm into uniform Prussian blue analogs (PBAs) single crystals (37-272 nm) while completely retaining their structural integrity. This internally encoded porosity enhances mass transport and confines reactive intermediates, boosting catalytic efficiency as demonstrated for ciprofloxacin oxidation. Time-resolved X-ray Absorption Fine Structure (XAFS) spectroscopy reveals the atomic scale origin of this process: contraction of the Mn-N bond from 1.46 to 1.39 Å directly links the relief of JTD strain to pore evolution. Thus, simple kinetic parameters such as temperature and time function as powerful and readily adjustable handles for precise porosity programming. This work may offer a generalizable strategy for rationally engineering porosity in a wide range of crystalline materials, with promising implications for sustainable energy and environmental applications.