Lithium-Ion-Induced Structural Constriction of Diatomic Metal-Organic Frameworks Promoting Photo(electro)chemical C-C...

Electron crowding within the skeletons of metal-organic frameworks (MOFs) has traditionally been overlooked, yet it represents a critical bottleneck in catalytic efficiency. Herein, we present a novel Li⁺-positioning diatomic MOF as a cathodic catalyst to mitigate current crowding during photoelectrochemical C-C coupling. Using the Li⁺-incorporated ZnPc-Pd₂DAC MOF, we demonstrate how the interplay between a local electric field and the lithium-ion shuttle effect induces a dynamic structural transformation of the diatomic nodes. Our findings reveal that sequential charging of Li⁺ at the chromophore center, followed by its discharging as Li^(1-δ)+ at the Pd₂ node, facilitates Li-ion electromigration along the MOF scaffold. This process drives the elastic structural evolution of the Pd₂ nodes, effectively alleviating electron crowding at the geometric constriction sites during electrolysis. Consequently, the formed *CO intermediates align parallel to each other with negligible geometrical distortion and strong dipole-dipole interactions. Furthermore, the significant overlap between the (Pd-d) and *CO orbitals facilitates the splitting of the bonding and antibonding orbitals, thereby lowering the energy levels of the *C₁ species. As a result of the minimized electron crowding, the (ZnPc-Pd₂DAC)@Li-3 catalyst exhibits a high current density and superior selectivity for CH₄ and acetate compared to its pristine counterparts. This work provides crucial insights into the electrochemical structural evolution of MOF catalysts, advancing the development of novel photocathode materials.