The phase and energy-level evolutions in seven distinct sequential states and their hierarchical memory effect of isomeric MOFs.

The emerging multi-phase evolution of metal-organic frameworks (MOFs) is advancing condensed matter physics and dynamic chemistry toward the next holy grail beyond current remarkable successes. To clarify the complex interplay between static and dynamic structure/energy factors governing molecular connection reservation, dissociation, and aggregation, the first serialized MOFs multi-phase evolutions were identified containing seven relevant phase states. The starting three MOFs with isomeric frameworks, that are [Co2L4]·2DMF, [CoL2]·DMF, and [CoL2]·2DMA (labeled as c1-c3, state Ⅰ), transform to similar hydrated products h1-h3 (stateⅡ), which are comparable to hydrogen-bonded framework [CoL2(H2O)4] (c4). Thermal dehydration of h1-h3 and c4 led to disorder and porous frameworks p1-p4 (state Ⅲ), which underwent glass transition to super-cooled liquid scl1-scl4 (state Ⅳ, ΔTscl = 10-24 K). MOFs glasses g1-g4 (state Ⅴ, Tg = 509-513 K) and re-crystallized MOFs rec1-rec4 (state Ⅵ, Tc = 535-547 K, analogues of de-solvated c2) were generated from queching and overheating scl1-scl4. Glass-recovered crystals r1-r4 (state Ⅶ, comparable to c2 or c3) were harvested by soaking g1-g4 in DMF or DMA solvents. For the first time, the enthalpy change between different phase states and their precise energy levels were established. The MOF glasses possess CO2 accessible porosity with a broad pore size range of 4-15 Å, and can be fabricated to be a crack-free membrane. These results demonstrate a concept of hierarchical memory effect, characterized by self-adaptive yet limited distortion of metal nodes driven by coordinative bond reversibility, restricted ligand movement in condensed state, and divergencer/convergence during framework disassembly/reassembly. This effect elucidates the origins of phase state evolution, offering new insights into MOF dynamic chemistry and advancing it to unexplored frontiers.