Electrochemical CO₂ reduction (CO₂RR) toward single-carbon products such as methane is an attractive route for sustainable chemical production, yet conventional Cu-based electrodes typically show negligible C1 selectivity, favoring instead H₂ evolution or, under pulsed-current operation, multicarbon products such as ethylene. Previous reports indicate that pulsed-current protocols applied to metallic Cu electrodes tend to promote C–C coupling and steer selectivity toward ethylene rather than methane. Copper metal–organic frameworks (MOFs) have emerged as attractive precatalyst platforms for CO₂RR, since their well-defined Cu coordination environments and they can be tuned to steer the in situ reconstruction pathways to generate specific active sites under reaction conditions. Here, we investigate CuTRZ[1], a copper MOF built from Cu centers coordinated by 1,2,4-triazole ligands, generated by anodic electrodeposition (AED) directly onto a Cu-particle electrode, and show that, under a pulsed-current protocol, its structural evolution diverts selectivity toward methane instead of the ethylene typically reported for metallic Cu or the same MOF at normal constant current conditions.

Ex situ SEM reveals a pronounced morphological transformation over the course of pulsed electrolysis: the electrodeposited film shows a dense, granular morphology with average particle size ~1 μm, which evolves into a porous, sponge-like architecture of markedly smaller particles. We hypothesize that this reflects progressive reduction of the Cu-triazole framework under cathodic bias, generating small, isolated metallic Cu clusters stabilized by residual triazole coordination, favoring sequential CO hydrogenation to methane over C–C coupling.

AED enables conformal, well-adhered CuTRZ growth directly on the Cu-particle electrode, avoiding limitations of drop-cast layers. In a flow cell with an electrolyte formulated to promote MOF regeneration, a pulsed-bias protocol drives progressive restructuring during electrolysis. Faradaic efficiency toward methane rises from negligible values to a stabilized 29% after 160 min, while the unmodified Cu-particle electrode produces no detectable methane under identical conditions. This time-dependent activation, together with the SEM-observed morphological change, is consistent with an operando restructuring mechanism distinct from the pathways associated with ethylene selectivity in metallic Cu, which ongoing in situ characterization aims to establish directly.

Overall, this work identifies electrodeposited triazole-based Cu-MOF layers, combined with pulsed-bias restructuring toward isolated Cu clusters[2] and a regeneration-promoting electrolyte, as a strategy for redirecting pulsed-current CO₂RR selectivity from ethylene toward methane, a pathway not accessible with conventional metallic Cu electrodes under equivalent conditions.