Crystal‐Facet Engineering of Mesoporous CuS Cascade Nanoreactors Enhances Photocatalytic C−C Coupling of CO₂‐to‐C₂H₄

Abstract Crystal‐facet heterojunction engineering of mesoporous nanoreactors with highly redox‐active represents an efficacious strategy for the transformation of CO 2 into valuable C 2 products (e.g., C 2 H 4 ). Herein, hollow mesoporous cube‐like CuS nanoreactors (~860 nm) with controlled anisotropic crystal‐facets are prepared through an interfacial‐confined ion dynamic migration‐rearrangement strategy. The regulation of the S 2− ion concentration facilitates the modulation of the highly active (110) to (100) crystal‐facet ratios from 0.119 to 0.288, and induces the formation of anisotropic crystal‐facet heterojunctions. The controllable crystal‐facet heterojunctions trigger the directional charge carrier migration, and are accompanied with the formation of tandem S‐defect sites (Cu 0 ‐S 1 @S 3 ). Both of them promote the efficient electron‐hole pair dissociation and attain asymmetric C−C coupling. The hollow mesoporous CuS nanoreactors with optimized crystal‐facet ratio of 0.224 (HMe‐CuS‐3) deliver a high selectivity of 72.7 % for the photocatalytic reduction of CO 2 to acetylene (C 2 H 2 ). Further constructed Au‐(110) and Co 3 O 4 ‐(100) spatially separated cascade nanoreactors (SS‐Au@Co 3 O 4 ‐CuS) achieve CO 2 ‐C 2 H 4 photoreduction, in which the Co‐sites enhance H 2 O dissociation to provide protons and the protonation of *CO to *COH. The *COH is further captured by Au‐sites to accomplish the asymmetric *CO‐*COH coupling and subsequent protonation, ensuring a high C 2 H 4 generation rate of 4.11 μmol/g/h with a selectivity as high as 90.6 %.