Engineering MXenes for Thermal and Photothermal Catalysis.

Heterogeneous catalysis relies on advanced, tunable materials offering structurally defined active sites and large accessible surface areas. Among the various material types, two-dimensional nanomaterials with high aspect ratios feature a high fraction of exposed atoms and thus efficient atom utilization. After more than a decade since the first report of MXene synthesis, these two-dimensional transition-metal carbides and nitrides, composed of alternating one-atom-thick metal and carbide/nitride layers with surface terminations, have found applications in diverse catalytic areas. This review focuses on the use of MXenes as solid catalysts in thermal or photothermal reactions, while electro- and photocatalysis are excluded as they have been extensively reviewed elsewhere. Section 2 briefly summarizes MXene synthesis and structural features, followed by Section 3 describing the nature and characterization of catalytically active sites, including surface groups, vacancies, and metal-support interfaces that arise from the synthesis conditions. Section 4 emphasizes best practices for ensuring reproducible and stable catalytic performance, with turnover frequency as a key comparative metric. Sections 5 and 6 highlight some representative thermal and photothermal reactions, underscoring the high light-to-heat conversion efficiency of MXenes. This review concludes with current challenges and future prospects, anticipating rapid progress with MXene-based heterogeneous catalysis.