Pressure Engineering Toward Harvesting the Bright Deep‐Blue‐Light Emission in Y‐based Metal‐Organic Frameworks

Abstract

The emergence of metal‐organic frameworks (MOFs) provides a new platform of low‐cost and color‐saturated blue light‐emitting diodes ideal for display and solid‐state lighting applications. However, numerous established MOFs still exhibit weak deep‐blue‐light emission (<450 nm) owing to low energy/charge transfer efficiency. Here a pressure‐treated strategy to greatly enhance photoluminescence performance of deep‐blue light‐emitting Y(BTC)(H2O)6 (H3BTC: benzene‐1,3,5‐tricarboxylic acid) is reported. Pressure‐treated Y(BTC)(H2O)6 exhibits a bright emission at 409 nm with a photoluminescence quantum yield from the initial 2.8% increasing to 75.0%. The hydrogen bonding cooperativity effect increases hydrogen bond binding energy after pressure treatment and thus the planarization structure is locked. The increased electronic transition diversity and oscillator strength originating from the planarization structure are highly responsible for boosting metal‐to‐ligand charge transfer. The findings in this study provide significant insights into the underlying mechanism of the structure‐property relationship in Y(BTC)(H2O)6 and offer a promising strategy to harvest deep‐blue‐emitting MOFs materials.

Dynamically responsive photonic metal–organic frameworks

“…In addition, the same group found that a nonemission MOF-2 and YðBTCÞðH 2 OÞ 6 also exhibit pressureresponsive photoluminescence. 127,128 Moggach et al also reported pressure-induced photoluminescence of Hf-peb MOF due to the linker rotation. 129…”

“…Further research suggests that the mechanism of this pressure-responsive MOF can be attributed to the enhanced hydrogen bonds lock causing enhanced intersystem crossing to effectively drive ligand-to-metal energy transfer. In addition, the same group found that a non-emission MOF-2 and Y(BTC)(normalH2Ofalse)6 also exhibit pressure-responsive photoluminescence 127 , 128 . Moggach et al.…”

Nanoporous Organic Frameworks as Light-Emitting Diodes: A Review

“…52 On the other hand, the yttriumbased MOF, [Y(BTC)(H 2 O) 6 ], has shown enhanced blue emission with an increase in the PLQY from 2.8% to 75.0% upon applying increasing amounts of pressure, followed by the release of pressure. 55 After a series of crystal structure analyses, the amplified PLQY values were attributed to stronger hydrogen-bonding interactions at a higher pressure, which would, in turn, lead to enhanced planarization of the structure composed of the yttrium center and the three benzene rings connected to it, allowing more conjugation and charge transport. 55 Another example is OX-2, which is composed of BDC linkers (H 2 BDC = 1,4-benzenedicarboxylic acid) bound to silver ions (Ag + ).…”

“…55 After a series of crystal structure analyses, the amplified PLQY values were attributed to stronger hydrogen-bonding interactions at a higher pressure, which would, in turn, lead to enhanced planarization of the structure composed of the yttrium center and the three benzene rings connected to it, allowing more conjugation and charge transport. 55 Another example is OX-2, which is composed of BDC linkers (H 2 BDC = 1,4-benzenedicarboxylic acid) bound to silver ions (Ag + ). It could be synthesized in different solvents to give isostructural OX-2 w (water), OX-2 m (methanol), and OX-2 DMF (N,N-dimethylformamide), which only differ from each other by the encapsulated solvent molecules.…”

“…Indium MOFs with π-conjugated carboxylate ligands are usually fluorescent due to their strong In–O bonds, 4d 10 configuration of In 3+ , charged building blocks, and delocalized π-electron system, − whereas CPM-5-Cl shows promising applications in blue LEDs with strong emission at 425 nm upon photoexcitation, corresponding to a remarkable bathochromic shift with respect to the emission of free H 3 BTC at 332 nm (Figure a,b) . On the other hand, the yttrium-based MOF, [Y(BTC)(H 2 O) 6 ], has shown enhanced blue emission with an increase in the PLQY from 2.8% to 75.0% upon applying increasing amounts of pressure, followed by the release of pressure . After a series of crystal structure analyses, the amplified PLQY values were attributed to stronger hydrogen-bonding interactions at a higher pressure, which would, in turn, lead to enhanced planarization of the structure composed of the yttrium center and the three benzene rings connected to it, allowing more conjugation and charge transport …”