MOF-Derived <i>In Situ</i> Confinement ofCopper/Copper Oxide Nanoparticles Inside a Carbon Tube: A Facile MorphologicallyControlled Synthesis Strategy for Superior Visible-Light-Driven PhotocatalyticEfficiency

A facile <i>in situ</i> process was developed to confine Cu_<i>x</i>O/Cu (<i>x</i> = 1,2) nanoparticles (CUO) inside a carbon tube (CT) to create composites (CUO-iCT) via a morphology-controlled synthesis that exhibits remarkable photocatalytic efficiency. Through a single precursor, CUO could be trapped inside the CT, thereby overcoming two major barriers that have limited photocatalytic efficacy of CUO and carbon composite derived from metal–organic framework (MOF)-based material: aggregation/agglomeration of CUO and improper alignment of the band structure. The best-performing CUO-iCT composite demonstrated 98 and 92% decompositions of cationic and anionic dyes under visible light for 80 min, twice that of the standard commercial photocatalyst (TiO₂). Moreover, the photocatalytic reaction showed a rate constant 17 times greater than that of the photolysis reaction with excellent recyclability. The remarkable efficiency of CUO-iCT is due to the synergetic effect of well-dispersed CUO in CT, leading to a reduced band gap, red shift in light absorption, rich active sites, high surface-to-volume ratio, prolonged <i>e</i>^<i>‑</i><i>–h</i>^<i>+</i> separation, and confinement effect.