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.
Wang et al. (Tue,) studied this question.