Carbonyl‐Anchoring Stabilized Copper Single Sites with Cavity‐Enhanced Mass Transport for Acetylene‐to‐Ethylene Electrosynthesis

Controlling mass transfer and adsorption in single‐site catalysts is critical for the activity and selectivity of heterogeneous electrocatalytic hydrogenation, but structural fragility at large current densities (≥200 mA cm −2 ) makes their practical application challenging. Here, taking acetylene (C 2 H 2 ) hydrogenation to ethylene (C 2 H 4 ) as an example, cucurbit[6]uril‐coordinated copper (CB[6]‐Cu) is theoretically predicted and experimentally proven to be the desired carbonyl‐anchoring isolated Cu site with engineered mass transport. CB[6]‐Cu demonstrates an outstanding Faradaic efficiency of 95.4% for C 2 H 4 , which significantly suppresses the competitive coupling and hydrogen evolution reactions at 300 mA cm −2 , with a turnover frequency of 2.91 s −1 and 65 h of continuous stable operation. The distinctive C 2 H 2 adsorption configuration and broken hydrogen bond network are revealed to result in optimal coverage and a sufficient supply of C 2 H 2 feedstocks, accounting for the remarkable C 2 H 4 performance. The extended CB[6]‐Co also exhibits enhanced NO‐to‐NH 2 OH electrosynthesis performance, highlighting its potential.