Near-Infrared Photothermally Enhanced Oxidation of Amines by Modified MXene Composites

Abstract

MXenes are two-dimensional nanomaterials with strong near-infrared (NIR) absorption and high photothermal conversion capability. However, their catalytic applications in the NIR region have been constrained by insufficient catalytic activity and the intrinsically low photon energy in this spectral range. To break this bottleneck, (3-aminopropyl)triethoxysilane is used to covalently modify titanium carbide MXene (Ti3C2TX) to obtain aminated NH2–Ti3C2, which is further electrostatically assembled with catalytically active transition-metal-substituted Keggin-type polyoxometalates (POMs), affording POMs@NH2–Ti3C2 composites. Under NIR irradiation, these catalysts generate the localized photothermal effect around the catalytic centers, efficiently driving the oxidation of tetrahydroquinoline derivatives. The precise synergy between photothermal and catalytic centers enables near-unity product selectivity, suppressing byproduct formation and thus minimizing organic solvent waste. Under photothermal conditions, the system achieves a turnover frequency as high as 154.3 h–1, far surpassing that of conventional external heating at the same temperature and outperforming most non-noble-metal and even noble-metal catalysts. This work not only expands the photothermal applications of POM-based composites but also demonstrates a feasible strategy for driving green catalytic transformations using light as a remote heat source, offering new insights into the synergistic development of energy-input saving and separation-process minimization for fine chemical synthesis.