<p>The electrochemical reduction of CO₂ to value-added carbon products is hindered by low Faradaic efficiency and competing hydrogen evolution. Here, we address this challenge by investigating how metal and C–N composition, layer thickness, and 2D heterostructure coupling influence CO₂ activation and selectivity in emerging 2D materials. A suite of Ti₂NT_x, Ti₄N₃T_x, Ti₃CNT_x, V₂NT_x, V₂CT_x, MoS₂/Ti₂NTₓ, and MoS₂/Ti₄N₃T_x were synthesized via a top-down etching method and evaluated for CO₂RR alongside hydrogen evolution. Ti-based nitride MXenes showed minimal CO₂RR activity and strongly favored HER, with layer thickness and MoS₂ coupling showing little effect on CO₂RR product distribution. Incorporating both carbon and nitrogen in Ti₃CNT_x moderately improved performance, yielding FE of ~25–30% for CO and ~8–10% for HCOOH. A more substantial enhancement was achieved by altering the metal center: V₂NT_x reached ~50% CO and ~18% HCOOH selectivity while suppressing HER at moderate current densities and maintaining stability over extended operation. DFT calculations reveal that Ti-based MXenes favor HER due to facile water dissociation and strong Ti–O interactions, whereas V-based MXenes stabilize HCOO* intermediates via termination-mediated hydrogen bonding, lowering the CO₂RR overpotential. These results elucidate composition–structure–activity relationships for rational design of selective 2D electrocatalysts.</p><p></p>