<p>Two-dimensional (2D) oxide nanomaterials have great potential for various applications but face challenges due to strong interlayer interactions. In this work, we propose a novel and facile method to exfoliate layered transition metal oxides into ultrathin nanosheets functionalized with phosphate species by the combination of ball-milling and liquid-exfoliation with phosphoric acid. The resulting HNbMoO₆ nanosheets with supported Pd nanoparticles displayed excellent catalytic performance in the one-pot conversion of phenol into caprolactam (CPL), achieving a yield of up to 71.9%. This one-pot route avoids the energy-intensive intermediate separation process in conventional multi-step approaches to CPL. The superior catalytic performance of the catalysts is attributed to the tunable Bransted acid/Lewis acid ratio and readily accessible active sites on the ultrathin nanosheets. This research demonstrates a new methodology for constructing ultrathin nanosheets and preparing bifunctional catalysts for tandem reactions, which opens the way for one-pot production of CPL.</p>