Rubo Fang, L. Xu, Yanhong Cui, Qingtao Wang, Yingxue Qin, Yiqi Xu, Qianjun Zhang, Qianjun Zhang, Yingkai Wen, Jia Zhao, Feng Feng, Tulai Sun, Xiaoliang Xu, Yihan Zhu, Chunshan Lu, Qianzhe Zhang, Qianzhe Zhang, Lili Lin, Xiaonian Li
Heterogeneous single-atom catalysts are typically stabilized by rigid anchoring to solid supports, which limits their dynamic response under the reaction conditions. Here, we demonstrate that liquid-metal-like catalytic behavior can be realized in heterogeneous systems through a liquid coordination environment rather than a liquid-metal phase. An ionic liquid membrane is introduced onto Al 2 O 3 to construct a high-loading single-ion Cu catalyst, in which reversible coordination exchange between N-heterocyclic carbene and Cu generates dynamically reconfigurable active centers. Spectroscopic analyses reveal the coexistence of NHC–Cu and Bis-NHC–Cu species with an average Cu coordination number of 2.5 ± 0.8 and a continuously tunable valence state between Cu + and Cu δ+ . In acetylene-selective hydrogenation, the catalyst achieves 98% C 2 H 2 conversion and 92% ethylene selectivity at 200 °C with only 0.25 wt % Cu, exhibiting a 35 °C lower half-conversion temperature than CuCl/Al 2 O 3 and stable performance over 200 h. Kinetic and operando spectroscopic studies demonstrate that the liquid coordination environment strengthens acetylene adsorption while weakening ethylene binding; density functional theory calculations further reveal a reduced H 2 dissociation barrier, enhanced C 2 H 2 adsorption, suppressed C 2 H 4 binding, and an inhibited further hydrogenation of *C 2 H 5, collectively directing the reaction toward selective semihydrogenation. This work establishes coordination dynamics as a general route to dynamic, self-adaptive, single-atom catalysis beyond static anchoring strategies.