Lewis acidic ionic liquid-POM hybrids enable efficient photocatalytic NH₃ synthesis by accelerating the capture and activation of N₂

Photocatalytic nitrogen reduction reaction (pNRR) under ambient conditions offers a sustainable alternative for ammonia synthesis, yet is hindered by inefficient photocatalyst design. Herein, we develop a Keggin-type polyoxometalate (POM)-based organic–inorganic hybrid photocatalyst, P4FeHPMo, by confining phosphomolybdic acid (PMA) with a Lewis acidic ionic liquid (IL) comprising symmetric tetrabutylphosphonium cation and transition metal-centered anion [FeCl₄]⁻. This confinement strategy leverages IL cations to direct the self-assembly of heterogeneous frameworks while the strongly Lewis acidic [FeCl₄]⁻ anions occupy interstitial sites and modulate the electronic structure of the POMs. This dual molecular-level interface regulation enables efficient N₂ accumulation and chemisorption by modulating the local microenvironment and electronic structure of active sites. As a result, P4FeHPMo achieves a remarkable ammonia production rate of 25 μmol·g_cat⁻¹·h⁻¹ without any sacrificial agents.