Dynamic Proton Extraction from Supramolecular Functionalized Metal–Organic Framework/Ti ₃ C ₂ MXene Hybrids for Efficient Solar Ammonia Synthesis

In N₂ photoreduction, photogenerated holes and electrons are involved in H₂O photolysis for proton supply and the weakening of the N≡N triple bond for N₂ activation, respectively. Rationally regulating the structure-activity relationship of these catalytic sites for available generation of charge carriers is crucial for optimizing N₂-to-NH₃ conversion efficiency. Herein, a robust photothermal catalyst carboxyl-enriched supramolecular (perylene tetracarboxylic acid, PTA) functionalized MIL-125(Ti)/MXene having dynamic proton extraction sites is designed for efficient N₂ photoreduction. Among these, MIL-125(Ti), PTA, and Ti₃C₂ MXene are, respectively, responsible for N₂ activation, reliable proton supply through interconversion between Brønsted acid and its conjugated base, and a photothermal response for accelerated reaction kinetics. The synergistic collaboration of these functionally distinct modules enhances light harvesting and responsiveness for dynamic multielectron/proton extraction, thereby facilitating feasible photothermal catalytic ammonia production. Remarkably high solar-to-ammonia conversion rates of 314.5-654.7 μmol g⁻¹ h⁻¹ are achieved under 100-500 mW cm⁻² illumination. This work provides insights into the rational design of an efficient solar ammonia synthesis system.