Multi‐Photon Absorption in Metal–Organic Frameworks

Abstract

Multi-photon absorption (MPA) is among the most prominent nonlinear optical (NLO) effects and has applications, for example in telecommunications, defense, photonics, and bio-medicines. Established MPA materials include dyes, quantum dots, organometallics and conjugated polymers, most often dispersed in solution. We demonstrate how metal-organic frameworks (MOFs), a novel NLO solid-state materials class, can be designed for exceptionally strong MPA behavior. MOFs consisting of zirconium- and hafnium-oxo-clusters and featuring a chromophore linker based on the tetraphenylethene (TPE) molecule exhibit record high two-photon absorption (2PA) cross-section values, up to 3600 GM. The unique modular building-block principle of MOFs allows enhancing and optimizing their MPA properties in a theory-guided approach by combining tailored charge polarization, conformational strain, three-dimensional arrangement, and alignment of the chromophore linkers in the crystal.

Confinement of Perovskite‐QDs within a Single MOF Crystal for Significantly Enhanced Multiphoton Excited Luminescence

“…Insets of Figure 5a-d also show the luminescence microscopy images of the same isolated ZJU-28⊃MAPbBr 3 crystal upon excitation of 960, 1440, 1800, and 2100 nm, respectively. [6,7,23,28] To investigate the MPE photostability, the Figure 5e,f shows the continuing illuminationtime-dependent MPE luminescence intensity spectra of the isolated ZJU-28⊃MAPbBr 3 crystal upon femtosecond laser excitation at 960 and 1440 nm, respectively. The comparison between the normalized single-photon-excited PL spectra and multiphoton excited photoluminescence (MEPL) spectra of ZJU-28⊃MAPbBr 3 with different sizes of MAPbBr 3 -QDs are displayed in Figure S7 (Supporting Information).…”

“…In fact, to the best of our knowledge, photostability of high-order MPE luminescence has not been reported yet. [6,7,23,28] To investigate the MPE photostability, the Adv. Mater.…”

Pressure‐Induced Multiphoton Excited Fluorochromic Metal–Organic Frameworks for Improving MPEF Properties

“…[2a, 3] Furthermore,t he pressure-induced fluorochromic materials reported to date are basically originated from one-photon excited fluorescence (1PEF) with such drawbacks of weak spatial confinement, limited penetration depth and low optical resolutions. [4] By contrast, two-photon excited fluorescence (2PEF) or multiphoton excited fluorescence (MPEF) materials undergo more complicated and fascinating processes in which two or more photons from al ow-energy radiation (usually in visible or NIR region) are absorbed by the material simultaneously, reaching the excited states,a nd emitting photoluminescence when transiting back to the ground state.A sar esult, MPEF materials are endowed with specific advantages including tight photonic focusing,deep tissue penetrating,less Rayleigh scattering,a nd low cell damage,w hich are beneficial for applications in high-density data storage,l ong-range telecommunication, high-grade anticounterfeit measures,i nvivo biological imaging,a nd so on. [5] It can be expected that the combination of pressure-induced fluorochromic process and MPEF together in one single material might afford more advanced and intriguing photophysical properties with enticing applications.…”

White‐Light Emission from Dual‐Way Photon Energy Conversion in a Dye‐Encapsulated Metal–Organic Framework

“…[1][2][3][4] Up to now,enormous materials have been developed to possess WLE performance,i ncluding carbon quantum dots, [5] polymers, [6][7][8] perovskites, [9][10][11][12] metalorganic materials, [13][14][15][16][17][18][19][20][21][22] and so on, providing great promise in solid-state lighting (SSL), anticounterfeiting,s ensing and detecting,a nd so on. [24][25][26][27] Therefore,p hoton color tuning materials by TPEF process are especially applicable in biological, laser, and telecommunication fields. Alternatively, WLE can also be achieved by photon up-conversion process, applying NIR excitation with low photon energies.However, such implementation has so far been restricted in rare-earth-doped inorganics,w hich are facing the urgent problem of scarce resources and environmental issues.…”

“…Such emission undergoes atwo-photon absorption (TPA) process,b earing the advantages of deeper tissue penetration, tight focusing area, reduced autofluorescence, and improved signal-to-noise ratios. [24][25][26][27] Therefore,p hoton color tuning materials by TPEF process are especially applicable in biological, laser, and telecommunication fields. [28][29][30][31][32] However,asfar as we know,nostrategic example has been reported so far to emit reliable TPEF white light.…”