Series of Luminescent Lanthanide MOFs with Regular SHG Performance

Abstract

Second-harmonic generation (SHG) is a kind of nonlinear optical phenomenon which has been widely used in optical devices, and factors influencing its signal are very complex. Here, taking advantage of excellent structural designability and overcoming the limitations of various coordinations of lanthanide metals, for the first time a series of lanthanide metal–organic frameworks (Ln-MOFs) with one particular ligand were synthesized and structurally characterized to study the interference of the SHG signal. The optical performance including single-photon fluorescence and SHG was collected and analyzed. It is found that all 13 kinds of Ln-MOFs can be divided into 2 crystal configurations by their individual space groups and Ln-MOFs with coordinated metal atoms from La to Tb possessing the noncentrosymmetric C2 space group exhibit the SHG property, the intensity of which depends on the type of metal atoms, the pumping wavelength, and the size of the single-crystal particles. This is the first time that the relationship between the nonlinear optical properties and the structure, metal atoms, pumping wavelength, crystal size of the whole series of Ln-MOFs is studied systematically, providing a lot of interesting results and enriching the research scope of nonlinear optics and materials science.

Noncentrosymmetric Lanthanide-Based MOF Materials Exhibiting Strong SHG Activity and NIR Luminescence of Er3+: Application in Nonlinear Optical Thermometry

“…Importantly, for both complexes, the DTA analyses revealed good thermal stability (up to 180 °C), which is a prerequisite for high-temperature sensor studies. Please note that in contrast to the known examples of Ln-MOFs that exhibit SHG properties, they necessitate ligands acquired through multistep synthetic procedures, ,, whereas the Ln-MOFs synthesized herein are obtained in a one-pot procedure from simple, achiral and readily available substrates (see also Schemes 1 and 2 in the SI).…”

“…28,31 Hence, the SHG phenomena are commonly utilized in photonics, laser technology, microscopy imaging, sensing techniques, and so on. 17,18,[28][29][30]32 Nowadays, the vast majority of modern, optically active luminescent materials are based on lanthanide ions. 31,33−35 This is mainly due to their (I) unique, ladder-like electronic structure, resulting in the abundance of emission lines in the UV, visible, and NIR spectral ranges; (II) characteristic and narrow absorption and emission bands, associated with shielding of the 4f electrons by the 5s and 5p ones; and (III) long emission lifetimes (μs−ms), originating from the forbidden intraconfigurational 4f−4f transitions.…”

“…The SHG phenomenon is an instantaneous and polarization-sensitive process, based on the energy conversion of the lower-energy fundamental beam, passing through the nonlinear optical medium, into the frequency-doubled second-harmonic beam. , In other words, two low-frequency (ω) photons are converted into a single photon of high frequency (2ω). Importantly, the whole electromagnetic energy is conserved during the SHG process, and there is no real absorption of the incident light (fundamental beam) by the nonlinear optical medium, limiting the intrinsic, laser-induced heating of the system and the undesired photobleaching phenomena (SHG is governed by the virtual excited states). , Hence, the SHG phenomena are commonly utilized in photonics, laser technology, microscopy imaging, sensing techniques, and so on. ,,− , …”

A Discrete 3d–4f Metallacage as an Efficient Catalytic Nanoreactor for a Three-Component Aza-Darzens Reaction

“…The coordination-driven self-assembly of polymetallic lanthanide complexes, including lanthanide helicates, lanthanide molecular cages, lanthanide coordination polymers, lanthanide clusters, and lanthanide metal–organic frameworks, has received fairly extensive attention in the field of chemistry and materials science . These polymetallic complexes not only often present unexpected structural aesthetics due to their inherent f orbital nature and high coordination numbers of lanthanide ions but also can provide a great number of catalytic active centers or subtle interactions between two or more metal ions, endowing them with an irreplaceable function and great potential applications in sensors, catalysis, magnetics, and so on. − In particular, coordination nanocages constructed on polymetallic lanthanide assemblies or container molecules have a unique environment within their cores, which can recognize guest molecules according to the size of the internal space and stabilize the transition state of molecules .…”

Fluorescence detection of malachite green and cations (Cr3+, Fe3+ and Cu2+) by a europium-based coordination polymer

“…Due to multiple coordination modes and remarkable uorescence characteristics, [44][45][46][47][48][49][50][51][52][53] lanthanide CP (such as Tb-CP, Eu-CP) have been widely employed in uorescent detection, [54][55][56][57][58][59][60][61][62][63][64][65] such as detecting metal cations, 66-75 inorganic anions, [69][70][71][72][73][74][75] small organic molecules [76][77][78][79][80] and explosives. [81][82][83] However, it is rarely recorded that lanthanide CP as multifunctional luminescent probe dedicated to detecting MG and various metal ions.…”