Lanthanide-doped metal-organic frameworks with multicolor mechanoluminescence

Abstract

Metal-organic frameworks (MOFs) and mechanoluminescent (ML) materials have been considered as two types of promising materials that have their own application fields. It would be amazing to endow one material with the advantages of ML and MOFs, thus broadening their applications. However, there are quite few investigations on this topic, and the ML mechanism in ML-MOFs remains unclear. In this study, we proposed a strategy for developing ML-MOFs by doping lanthanide ions into the non-centrosymmetric SBD ([Sr(μ-BDC)(DMF)] ∞) MOF, and successfully synthesized a series of lanthanide-doped MOFs Ln-SBD (Ln = Tb, Dy, Sm, Eu) and Tb 1−x Eu x-SBD (x = 0.2, 0.4, 0.6, 0.8) with multicolor ML. The lanthanide ions were uniformly distributed in the matrix of the SBD-MOF, and occupied the Sr site. The ML-MOFs exhibited intense multicolor ML emissions varying from green to yellow to red by changing the co-doping ratios and species of lanthanide ions. The similar ML and photoluminescence (PL) spectra indicated that the ML emission was assigned to the radiative transition from the excited states to the ground states of lanthanide ions. The radiative transition was induced by the electron bombardment process that originated from the piezoelectric effect of the non-centrosymmetric SBD host. In addition, a pioneering temperature sensing research based on ML was carried out, which is promising for realizing dual-functional detection of stress and temperature without excitation light sources. This study gives a unique insight for developing more versatile and interesting smart materials by combining the versatility of MOF with the ML emission, imparting additional values to both MOF and ML materials. Moreover, this study provides a general rule for selecting MOFs with an acentric structure as the host for ML materials.

Multi‐Emission from Single Metal–Organic Frameworks under Single Excitation

“…Some reviews have been reported for multi‐emission MOFs. [ 8,15,19 ] Here, we summarize the last advances in multi‐emission MOFs based on the excited sites and review the advances in the design strategies. The emission mechanisms, such as antenna effect, excited‐state intramolecular proton transfer (ESIPT), and tautomerism emission are discussed.…”

Alkaline-earth-metal-ion blending enhanced mechanoluminescence of lanthanide ions in MZnOS hosts for stress sensing and anticounterfeiting

“…Mechanoluminescence (ML) is the light emission generated via directly applying mechanical stimuli on ML materials; [1][2][3] this kind of energy transfer process has attracted tremendous attention for its promising applications in stress sensing, 4,5 energy harvesting, 6 wearable artificial devices 7,8 and information encryption anticounterfeiting devices. 9 Recent ML investigations mainly deal with organic-complexes [10][11][12][13] and inorganic-crystal hosts.…”

“…2,27,43 Although the rich energy level property of lanthanide ion dopants can be preserved in the MZnOS host, 31,44 the MZnOS with same lanthanide ion dopant usually exhibits the similar ML color, 27,45 because the emission color is mainly determined from corresponding maximum emission wavelength. 3,46,47 Since Wang demonstrated tunable ML color from lanthanide ion dopants via incorporating different lanthanides ions into the unary CaZnOS host, 44 the enhanced ML from lanthanide ion dopants is strongly anticipated for the possible application of ML in stress sensing and information encryption domains. 5,48,49 Recently, Zhang developed a (Ca, Sr)ZnOS host via partially replacing Ca 2+ in the CaZnOS host with Sr 2+ , and found that ML of Mn 2+ dopant in the binary host Ca 0.7 Sr 0.3 ZnOS is about one order of magnitude stronger than that in unary host CaZnOS.…”

Two Calcium Coordination Polymers with Multi‐Stimuli‐Responsive Properties

“…[21][22] Interestingly, the initial structure and luminescence properties can be recovered under fumigation, or immersion treatment, thereby realizing a reversible response. So far, the vast majority of LCP type SRL materials show the response that the emission wavelength moves from high energy level to low one under mechanical force stimulation, [23][24][25][26][27][28] that is, the emission peak is red-shifted, while the blue-shifted response of the emission wavelength from low energy level to high one is relatively rare. [29][30] The adjustment of the luminescence color before and after grinding stimulation in a controllable way is of great significance for the application of MCL materials.…”