Sculpting In‐plane Fractal Porous Patterns in Two‐Dimensional MOF Nanocrystals for Photoelectrocatalytic CO2 Reduction

Herein, by choosing few‐nm‐thin two‐dimensional (2D) nanocrystals of MOF‐5 containing in‐planner square lattices as a modular platform, a crystal lattice‐guided wet‐chemical etching has been rationally accomplished. As a result, two attractive pore patterns carrying Euclidean curvatures; precisely, plus(+)‐shaped and fractal‐patterned pores via ⟨100⟩ and ⟨110⟩ directional etching, respectively, are regulated in contrast to habitually formed spherical‐shaped random etches on MOF surface. In agreement with the theoretical calculations, a diffusion‐limited etching process has been optimized to devise high‐yield of size‐tunable fractal‐pores on the MOF surface that tenders for a compatibly high payload of catalytic ReI‐complexes using the existing large edge area once modified into a free amine‐group‐exposed inner pore surface. Finally, on benefiting from the long‐range fractal opening in 2D MOF support structure, while loaded on an electrode surface, a facilitated cross‐interface charge‐transportation and well‐exposure of immobilized ReI‐catalysts are anticipated, thus realizing enhanced activity and stability of the supported catalyst in photoelectrochemical CO2‐to‐CO reduction. A well‐controlled crystal lattice‐guided anisotropic etching of two‐dimensional (2D) MOF surfaces gives perforated hierarchical pore patterns that allow high‐loading of molecular catalysts exposed at the pore‐edges for efficient and stable photoelectrocatalytic CO2 reduction reaction.