Tailoring luminescent oxygen sensitivity via structural design and its application in pressure-induced emission enhancement

Abstract

Pressure-induced emission enhancement (PIEE) is relatively rare and holds greater research promise than pressure-induced emission quenching. However, reports on PIEE often overlook the influence of atmospheric oxygen, especially in porous materials. Additionally, since the impact of energy transfer between the excited state of luminescent probes and T₁(O₂) on oxygen sensitivity remains unclear, tuning the luminescence-based oxygen sensitivity at the molecular structural level is highly challenging. Here, we report a series of coordination polymers (CuXBP, X = I, Br, Cl). Although they have similar structures and comparable porosity, their oxygen quenching efficiencies differ significantly (ranging from 95.8% to 7.7%). Computational simulations reveal that the superior oxygen quenching efficiency of CuIBP stems from the minimal ΔE (742 cm⁻¹) between its T₁ state and T₁(O₂). Additionally, under pressure, both CuClBP and CuBrBP exhibit the commonly observed red shift accompanied by luminescence quenching. However, CuIBP displays the less commonly observed PIEE, attributed to the reduced porosity after grinding, which lowers oxygen-sensing efficiency (from 95.8% to 33.2%). Compared to its unground state, this efficiency reduction in CuIBP substantially attenuates oxygen-induced quenching, resulting in stronger luminescence (>2-fold enhancement) under ambient conditions. This work establishes a novel strategy for designing oxygen sensing and PIEE materials.