Nonlinear Optical Switching in Regioregular Porphyrin Covalent Organic Frameworks

Abstract

Covalent organic frameworks (COFs) have garnered immense scientific interest among porous materials because of their structural tunability and diverse properties. However,the response of such materials towardlaser-induced nonlinear optical (NLO) applications is hardly understood and demands prompt attention. Three novel regioregular porphyrin (Por)-based porous COFs-Por-COF-HH and its dual metalated congeners Por-COF-ZnCu and Por-COF-ZnNi-have been prepared and present excellent NLO properties.N otably,i ntensity-dependent NLO switching behavior was observed for these Por-COFs,w hichi sh ighly desirable for optical switching and optical limiting devices. Moreover,t he efficient p-conjugation and charge-transfer transition in ZnCu-Por-COF enabled ahigh nonlinear absorption coefficient (b = 4470 cm/GW) and figure of merit (FOM = s 1 /s o ,3565) value compared to other state-of-the-art materials, including molecular porphyrins (b % 100-400 cm/GW), metalorganic frameworks (MOFs; b % 0.3-0.5 cm/GW), and graphene (b = 900 cm/GW). Molecules/materialswithinherentnonlinearoptical(NLO)properties have profound importance in telecommunications, data storage,d isplay technologies,s ensors,a nd biomedical devices. [1] In this regard, molecular porphyrins have been widely studied because of their versatile optical and electrochemical properties,large and fast NLO responses,possibility of incorporating aw ide range of metals,a nd their good thermochemical stabilities for optical limiting and optical switching applications. [2] Nonetheless,t oenhance and tune optical nonlinearities of singular porphyrin moieties,b athochromic shifting of their absorption bands by large p-electron delocalization is crucial, which becomes possible through de novo design of integrated porphyrin units featuring extended p-conjugation. [3, 4] Along this line,w ep ropose ap orphyrin-linked covalent organic framework (COF) [5] as model system, wherein enhancement and switching of the NLO response can be studied by manipulation of the framework. Among the recognized crystalline materials, COFs are known for being mechanically robust and offering ahighly accessible surface area. Thestructural and electronic tunability of COFs have garnered particular interest in research areas such as adsorption/storage, [6] chemical sensors, [7] electronics, [8] and catalysis. [9] Despite such potential, COFs comprising porphyrin units have not been explored as NLO materials.F or this purpose,aregioregular ordering of multiple metal centers in ac rystalline 2D porphyrin framework-preferably without ap ost-synthetic modification-is desirable.T his challenging objective [10] has great potential in optoelectronics and photo/electrocatalysis applications.Herein, we present aconjugated imine-linked porphyrinhomopolymeric COF (Por-COF-HH; Figure 1a)prepared by Schiff base A4B4 condensation of 5,10,15,20-tetrakis(4-formylphenyl)-21H,23H-porphyrin (TFPP) and 5,10,15,20-tetrakis(4-aminophenyl)-21H,23H-porphyrin (TAPP). Adopting the same pathway,w ea lso synthesized regioregular...

Intramolecular Hydrogen Bonding-Based Topology Regulation of Two-Dimensional Covalent Organic Frameworks

“…Covalent organic frameworks (COFs), as one of emerging class of porous crystalline materials built from organic building blocks connected by covalent bonds, [1][2][3][4][5][6][7][8][9] have attracted widespread attention due to their various potential applications including gas adsorption and separation, [10][11][12][13] catalysis, [14][15][16][17][18] optoelectronics, [19][20][21][22] etc. [23][24][25][26][27][28][29][30][31] The functional diversity of COFs originates from their high structural tunability and versatility, in which a large variety of organic building blocks can be interconnected to create an almost infinite number of networks. [6][7][8][9] The overall properties of such porous materials are associated with their compositions and morphologies, but more critically rely on their network topologies.…”

Multibranched Octupolar Module Embedded Covalent Organic Frameworks Enable Efficient Two‐Photon Fluorescence

“…[45] The TPA cross section was derived from the two-photon emission spectra using a known standard Rhodamine 6G dye (R6G) in methanol with concentration of 10 −5 m as reference (Figure S21, Supporting Information). The TPA cross section of cyano-sp 2 c-COF was determined to be about 1225 GM per repeating unit (1 GM = 10 −50 cm 4 s photon −1 ) at 800 nm according to the literature reported calculation (see more details in Methods), [63][64][65] 1064 GM at 750 nm and 1073 GM at 780 nm and in methanol, which is higher than those of the corresponding model compound (≤104 GM) and many other previously reported TPA materials (Figure 4c and Table S3, Supporting Information).…”

“…Considering the fact that both CN and CC can offer effective conjugation, some COFs with imine linkages have been demonstrated as potential nonlinear materials recently. [34,35,65,72] However, the absence of strong electron acceptors or donors for imine-COF causes less efficient ICT and thus suppress the TPA response according to the literature. [34,40] Furthermore, TPA and strong OPF are simultaneously required for efficient TPF materials, but the absolute PLQY of imine-COF in solid state is only 0.1%.…”

A Theoretical Perspective on Strategies for Modeling High Performance Nonlinear Optical Materials

“…Liu et al, 2017), light generation and modulation (J. Chen et al, 2018), optical parametric amplification (Kumbhakar and Kobayashi, 2007;Popov and Shalaev, 2006), laser frequency conversion (D. Hou et al, 2018a), modulators (Grote et al, 2002), and optical switches (Biswal et al, 2019;. In addition, nonlinear optics have remarkable applications in dynamic image processing (Van Steenwinckel et al, 2001), sensing (Ray, 2010), high resolution imaging (Miller et al, 2002), optical computing (Hutchinson and Milburn, 2004), optical fiber communication (Arivuoli, 2001), optical data storage (Iliopoulos et al, 2010), and materials analysis (Y. R. Shen, 1989).…”