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

Crystal-facet heterojunction engineering of mesoporous nanoreactors with highly redox-active represents an efficacious strategy for the transformation of CO2 into valuable C2 products (e.g., C2H4). 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 S2- 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 (Cu0-S1@S3). 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 CO2 to acetylene (C2H2). Further constructed Au-(110) and Co3O4-(100) spatially separated cascade nanoreactors (SS-Au@Co3O4-CuS) achieve CO2-C2H4 photoreduction, in which the Co-sites enhance H2O 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 C2H4 generation rate of 4.11 μmol/g/h with a selectivity as high as 90.6%.