Quasi‐Closed‐Loop Crystal–Amorphous Solid–Wet Gel Transformation in Copper MOFs for Exceptional Cycling Stability in Cascade Reactions

Abstract

Abstract Quasi‐closed‐loop transformations between crystals, amorphous solids, and wet gels are rarely explored in metal–organic frameworks (MOFs). We report a stimuli‐responsive Cu(I)‐MOF (Cu‐cMOF) constructed from relatively stable 1D Cu(I) secondary building units (s‐SBUs) and unstable trigonal Cu(I) SBUs (us‐SBUs). This unique architecture enables quasi‐closed‐loop crystal‐amorphous solid‐wet gel transformations through the following steps: i) The crystalline framework first undergoes oxidative amorphization via Cu(I)‐to‐Cu(II) conversion at us‐SBUs, forming amorphous Cu‐aMOF; ii) Cu‐aMOF subsequently reorganizes into wet gel (Cu‐MOG) in preheated DMAc via oxygen‐ and dimethylamine‐assisted framework fragmentation and colloidal assembly; and iii) Cu‐MOG transforms back to Cu‐cMOF via a solvent‐mediated phase transition. The relative structural persistence of the s‐SBUs—in contrast to the labile us‐SBUs—confers a degree of reversibility to the system. Remarkably, mutual regulation between reaction conditions and catalyst structure is achieved in the azidation‐click cascade reaction. The azidation step drives the transformation of Cu‐aMOF into Cu‐cMOF, while the click reaction reverses this process. Each catalyst phase exhibits step‐specific catalytic selectivity, forming a self‐sustaining structural transformation cycle that maintains over 98% efficiency after at least 20 cycles. Additionally, used catalysts can be repurposed as Cu‐MOGs for large‐sized molecule adsorption. This work establishes a cooperative switchable system with adaptive multifunctionality.