Ni₃(HITP)₂@PTFE Molecular Fence Enables Selective C₂ Coupling in Methane Contact-Electro-Catalysis

Contact-Electro-Catalysis (CEC) enables methane activation under ambient conditions; however, the poorly understood interfacial active sites and uncontrolled evolution of reactive radical intermediates cause methane conversion to remain dominated by C₁ oxygenation rather than selective C─C coupling. Herein, we assemble the established Ni₃(HITP)₂ framework (HITP = 2,3,6,7,10,11-hexaiminotriphenylene) on PTFE (polytetrafluoroethylene) to construct a molecular fence interface integrating Ni-N₄ sites with spatial confinement for selective C₂ coupling. During CEC, contact electrification at the PTFE-water interface supports radical generation for methane conversion, while the coupled Ni-N₄ sites further facilitate O₂ activation and modulate reactive species utilization. Simultaneously, the porous Ni₃(HITP)₂ outer layer shows enhanced CH₄ uptake near the charged interface and is proposed to favor C─C coupling by promoting local methane enrichment and retention of methane-derived intermediates. As a result, methane conversion is redirected from C₁ oxygenation toward selective C₂ coupling under ambient conditions, delivering a C₂ yield of 0.58 mmol g^-1 h^-1 with 82.4% selectivity. In situ spectroscopy and density functional theory calculations support a mechanistic model in which interfacial Ni-N₄ sites and the porous framework jointly influence reactive-species utilization and methane-derived intermediate reactions, favoring pathway-selective methane CEC.