Pre-strain and release in MOF catalysts: Ligand-engineered strain storage for enhanced catalytic activity

The strategic exploitation of structural tension effects in heterogeneous catalyst design remains underexplored, particularly in programmable frameworks. Here, we engineer a bipyridyl-based metal-organic framework (MOF) platform (-CH₃, H, -CF₃) anchoring Cu(OTf)₂ for regioselective ring-opening of epoxides, demonstrating how programmable ligand geometry controls catalysis via strain effects. Both CH₃- and CF₃-modified MOFs show significantly enhanced catalytic activity, achieving turnover frequencies 3.4- and 4.7-fold higher than the unmodified MOF. Computational studies show this enhancement originates from torsional distortions in the bipyridyl ligands that create pre-strained frameworks. During the transition state, this accumulated strain energy is released through selective bond reorganization - a "pre-strain and release" mechanism that effectively lowers activation barriers. Mechanistic studies propose a hybrid epoxide ring-opening pathway that combines S_N2-like nucleophilic attack with S_N1-type bond cleavage selectivity. The m(Bpy-CF₃)-MOF-Cu(OTf)₂ catalyst demonstrates broad substrate versatility (yields: 78-99 %) while maintaining stability over 10 cycles. Gram-scale and one-pot sequential reactions confirm its practical utility. Our work establishes a "structural strain-activity" relationship that bridges classical strain engineering with framework materials, enabling new catalytic designs for sustainable chemistry applications.