Intrinsic Green Phosphor Containing a {Y₅O₂₂} Pentamer Unit and a Carbonate Ligand Generated In Situ from Squaric Acid

Abstract

An unexpected green phosphor! The promising activator‐free yttrium metal–organic framework (MOF) [Y5(OH)6(HCO2)3(CO3)2‐(C4O4)] ⋅2.5 H2O consists of unique {Y5O22} pentamers and four types of ligands, the carbonate group of which was unprecedentedly in situ generated from squaric acid. This pure yttrium–MOF compound displays intrinsic green light and has proven to be the first hybrid‐yttrium‐host lattice to achieve near‐white‐light solely through Eu3+ doping (see figure).

Efficient and tunable white-light emission of metal–organic frameworks by iridium-complex encapsulation

“…The quantum yield was measured and a value up to 20.4% was obtained ( λ ex =370 nm) for this sample. This value is the highest among all reported white-light-emitting MOFs 12 23 24 25 26 27 28 29 to this date ( Supplementary Table S4 ), and is approaching that of the best inorganic–organic hybrid semiconductor white-light emitters 36 . Photographs showing white-light emission of a 3.5 wt% [Ir(ppy) 2 (bpy)] + @ 1 sample under radiation at 365 nm (ultraviolet lamp) are given in Fig.…”

“…At an [Ir(ppy) 2 (bpy)] + concentration of 3.5 wt%, high-quality white light was obtained and the resultant material possesses CIE coordinates (0.31, 0.33) that are very close to those of pure white light and good colour quality (CRI ~80 and CCT ~5900 K). In addition, this material also has the highest emission quantum yield (up to 20.4%) compared with all MOFs reported to date 12 27 28 29 30 31 32 33 . The WLED assembly using an InGaAsN ultraviolet chip and this material can readily be fabricated.…”

“…The new composite emitter generates bright white light when excited at 370 nm with a quantum yield as high as 20.4%. This value is the highest among all white-light-emitting MOF materials reported to date 12 23 24 25 26 27 28 29 and is approaching the level of the best inorganic–organic hybrid semiconductor bulk materials 36 . At an [Ir(ppy) 2 (bpy)] + concentration of 3.5 wt%, the Commission International de I’Eclairage (CIE) coordinates, colour-rendering index (CRI) and correlated colour temperature (CCT) values were calculated to be (0.31, 0.33), 80 and 5900 K, respectively.…”

“…To date, only a few examples of direct white-light-emitting MOFs are realized 23 24 25 26 . Doping the framework structures by rare metals (for example, Eu 3+ , Tb 3+ and Dy 3+ ) at various concentrations may lead to white light 12 27 28 29 , but at low quantum yield 12 . Thus, it is essential to develop an effective method to obtain highly efficient, white-light-emitting MOF materials.…”

Magnetocaloric Effect of Two Gd-Based Frameworks

“…It is worth noting that the two cubanes on the left side of the butterfly-shaped unit are connected to the central Gd 3+ through two HCOO − and one CO 3 2− , while these on the right side of the butterfly-shaped unit are connected to the central Gd 3+ through one HCOO − and one CO 3 2− . Based on previous work, the ligands of CO 3 2− and HCOO − were generated from the decomposition of squaric acid in situ under hydrothermal conditions [29,30]. Adjacent butterfly-shaped units expand into a 2D layer of [Gd 5 (OH) 6 (HCOO) 3 (CO 3 ) 2 ] n 2n+ through sharing edges, as shown in Figure 1c.…”