Ultralong Near Infrared Room Temperature Phosphorescence in Cu(I) Metal‐Organic Framework Based‐on D–π–A–π–D Linkers

Abstract

Materials taking abundant advantage of triplet states luminescence have risen lots of attention in decades. In this work, a Cu(I) metal-organic framework (MOF) with synchronous metal-to-ligand charge transfer (MLCT) state and triplet emission of the ligand is synthesized from a D-π-A-π-D ligand with suitable energy gap. The Cu(I) MOF possessed MLCT emission in the range of 450-505 nm with microsecond lifetimes (1.07 to 5.38 µs) and a triplet state emission in near infrared (NIR) region ≈705 nm with lifetimes of 1.85 ms at 300 K and 25.16 ms at 77 K, much longer than those of reported Cu(I) MOFs. Moreover, a white light is obtained through adjusting the relative intensity of dual peaks. More importantly, NIR long persistent luminescence of Cu-MOF is observed by naked eyes under cryogenic condition. Multiple factors such as the delicate design of the D-π-A-π-D structure of ligand, the enhanced spin-orbital coupling by Cu(I) networks, and the tight packing mode of the framework promote the generation of MLCT emission and ultralong NIR room temperature phosphorescence. The combination of calculation and experiment to analyse the luminescence mechanism of Cu(I) MOFs provides ideas for the development of Cu(I)-based intelligently responsive materials with RTP properties.

Intriguing Room Temperature Phosphorescence in Crystalline Porous Organic Frameworks

“…After the formation of SUST-WZ3 MOF with Cu(I), the obtained Cu(I)-MOF showed an ultralong near infrared RTP with lifetime of 1.85 ms and a deep red LPL at 77 K due to the contribution of D-𝜋-A-𝜋-D ligand, the enhancement of SOC and the rigid microenvironment provided by MOF frameworks. [24] From the above discussions, it can be summarized that organic chromophores can be ossified in MOFs with ordered arrangement and showed enhanced RTP performance than that of free organic chromophores, moreover, RTP properties of MOFs can be regulated by controlling the packing style of organic Figure 6. Illustration of RTP Cd-MOFs prepared with 5-(1H-1,2,4-triazol-1-yl)nicotinic acid as the potential RTP species and organic linker as well as the cooperation of auxiliary bridging linkers (imidazole or benzimidazole derivatives).…”

Recent advances in the design of afterglow materials: mechanisms, structural regulation strategies and applications

“…Recently, inspired by D–A molecules, Wang et al designed a D–π–A–π–D ligand with TADF and phosphorescence emission characteristics at low temperatures. 211 After assembly into a MOFs with Cu( i ) nodes, dual phosphorescence emission incorporating Cu-based MLCT and RTP inherited from the ligand was realized, owe to the large energy gap between the two T n (Fig. 6d).…”

Organic Host‐Guest Materials with Bright Red Room‐Temperature Phosphorescence for Persistent Bioimaging†

“…Organic room‐temperature phosphorescence (RTP) materials have attracted immense attention due to their peculiar photophysical process and potential applications in advanced printable and writable security inks, [ 1‐4 ] high‐resolution bioimaging, [ 5‐7 ] microenvironment oxygen visual sensing and quantitative detection. [ 8‐11 ] Several attempts have been made to develop high‐performance RTP materials, including the introduction of heavy atoms or halogen/hydrogen bonding, [ 12‐17 ] doping in a rigid matrix, [ 18‐26 ] construction of metal‐organic frameworks, [ 27‐28 ] and ionic‐π interactions. [ 29‐31 ] However, limited RTP materials with long emission wavelengths are reported due to the lack of a preparation strategy.…”