Journal Article 2D Nb─O vacancy associates Research Support, Non-U.S. Gov't Review altered hydrogenation pathways asymmetric electron redistribution atomic layers black ultrathin CuCrP2S6 flakes black ultrathin CuVP2S6 flakes charge separation defect engineering electronic structure electronic-structure tailoring hybridization layered metal phospho–sulfides narrow bandgap near‐infrared‐responsive photocatalysts non-covalent interactions noncovalent interaction photocatalytic photocatalytic CO2 reduction photocatalytic nitrogen fixation polarized metal sites single-unit-cell Bi3O4Br ultrathin