<p>Cu-based nanocatalysts hold promise for the reverse water–gas shift (RWGS) reaction. However, irreversible sintering of the Cu catalyst for deactivation remains a persistent challenge under thermal or photothermal processes. In this study, we develop an anti-sintering catalyst using CuNiMgAl layered-double-hydroxide (LDH)-derived hydroxyl engineering to anchor ultrafine CuNi nanoparticles, achieving stable photothermal RWGS conversion. For Cu₃Ni-MA, the oxyphilic Ni dopants facilitate the formation of hydroxyl-coordinated Cu²⁺–Ni²⁺ species during the calcination of LDH-derived materials; meanwhile, the Ni incorporation enhances the plasmonic effect of CuNi nanocatalysts to drive H₂ spillover for hydroxyl replenishment under light irradiation, which is diverged from conventional Cu₃Ni alloy-based catalysts. This Cu₃Ni-MA achieves a CO production rate of 339.8 mmol g⁻¹ h⁻¹ with 98% selectivity, outperforming thermal catalysis by 3.5-fold in RWGS conversion. Notably, the catalyst exhibits robust photothermal CO₂ hydrogenation stability, preserving &gt;99% of its original activity and CO selectivity during 30 d of intermittent start–stop cycles and 280-h continuous testing. This study offers alternative perspectives for designing anti-sintering catalysts for photothermal catalytic systems by coupling dynamic hydroxyl regulation with plasmonic activation mechanisms.</p>