As the candidates for large-scale hydrogen storage, liquid organic hydrogen carriers (LOHCs) exhibit evident advantages in hydrogen storage density and convenience of storage and transportation. Among them, NECZ (N-ethylcarbazole)/12H-NECZ (dodecahydro-N-ethylcarbazole) is considered as a typical system with the lower hydrogenation/dehydrogenation temperature. However, the low dehydrogenation efficiency restrict its commercial applications. In this work, the single-layer Ti3C2Tx MXene was employed as the support to load the Pt nanoparticles for the 12H-NECZ dehydrogenation reaction. The effect of transition metals, loading amounts and morphologies of catalysts were analyzed. It was found that the 3 wt% Pt/S–Ti3C2Tx catalyst exhibited the best catalytic performance with 100% conversion, 91.55% selectivity of NECZ and 5.62 wt% hydrogen release amount at 453 K, 101.325 kPa for 7 h. The product distributions and kinetics analysis suggested that the elementary reaction from 4H-NECZ to NECZ was the rate-limiting step. The selectivity of NECZ is sensitive to the dehydrogenation temperature. Combined with the XRD, SEM, HRTEM, XPS, BET and FT-IR results, it could be indicated that the special two-dimension structure of S–Ti3C2Tx and electronic effect between Pt and S–Ti3C2Tx enhanced the dehydrogenation efficiency of 12H-NECZ. The measurements of cyclic dehydrogenation indicated that the Pt/S–Ti3C2Tx catalyst exhibited good stability after 42 h. This work brought a new strategy for the design of efficient catalysts using two-dimensional materials in the applications of the liquid organic storage hydrogen technology. Display omitted •The effect of active metals, loading amounts and morphologies of catalysts were analyzed.•The 3 wt% Pt/S–Ti3C2Tx catalyst exhibited the best catalytic performance.•The special structure and electronic effect enhanced the dehydrogenation efficiency.•The selectivity of NECZ was enhanced with the increase of temperature.•The elementary reaction from 4H-NECZ to NECZ was the rate-limiting step.