Fully Conjugated Two‐Dimensional sp²‐Carbon Covalent Organic Frameworks as Artificial Photosystem I with High Efficiency

Abstract

The synthesis of fully conjugated sp 2 -carbon covalent organic frameworks (COF) is extremely challenging given the difficulty of the formation of very stable carbon-carbon double bonds (-C=C-). Here,w er eport the successful preparation of a2 DC OF (TP-COF) based on triazine as central planar units bridged by sp 2 -carbon linkers through the -C = Ccondensation reaction. High-resolution-transmission electron microscopy( HRTEM) clearly confirmed the tessellated hexagonal pore structure with ap ore center-to-center distance of 2nm. Powder X-rayd iffraction (PXRD) together with structural simulations revealed an AA stacking mode of the obtained layered structure.T P-COF turned out to be an excellent semiconductor material with aL UMO energy of À3.23 eV and aband gap of 2.36 eV.Excitingly,this novel sp 2carbon conjugated TP-COF exhibited unprecedented coenzyme regeneration efficiency and can significantly boost the coenzyme-assisted synthesis of l-glutamate to arecord-breaking 97 %yield within 12 minutes.Long-range p-conjugated two-dimensional (2D) materials have received considerable attention in recent years and present ar ange of unique advantages over traditional polymeric materials. [1][2][3][4][5][6][7] In particular, the topological arrangement of aromatic units propagating in two spatial directions equips them with superior (photo-)electronic and magnetic properties. [8][9][10] However,t he delicate control over specific arrangements of functional units to obtain highly ordered 2D materials is still ag reat challenge. [11][12][13][14] Covalent organic frameworks (COFs) take advantage of the structural selfhealing properties stemming from dynamic covalent bond formation. [15][16][17][18][19][20][21] This advancement has made it possible to synthesize well-defined 2D structures with diverse functionalities.A mong all synthetic strategies of COFs,t he most frequently used dynamic covalent-bond-formations trategies are the Schiff base condensation reaction and the boronate ester bond formation. Despite the fact that the extended pconjugation can propagate through the -N = C-double bonds in the Schiff base structure,t he imine-linkage displays relatively poor stability and weak electron delocalization. To overcome this limitation, researchers have been actively exploring new reactions to construct fully conjugated COFs with an optimal electron delocalization. [22][23][24][25][26][27][28] However,examples of fully conjugated imine-free COFs with sp 2 -carbon double bond structures are still rare because it is extremely difficult to form -C = C-bonds via reversible coupling reactions and simultaneously gain the desired conjugation as well as the refined crystallinity within the COF structure.Recently, Jiang et al. and Feng et al. successfully constructed conjugated 2D COFs bearing -C = C-linkage by using Knoevenagel polycondensation. [29][30][31][32] Ther eported sp 2 -carbon linked 2D COFs were demonstrated to have excellent electrochemical and charge-transfer properties.Thee nhanced electron delocalization of sp 2...

Regenerable and stable sp2 carbon-conjugated covalent organic frameworks for selective detection and extraction of uranium

“…Although the sp 2 -carbon bond are very stable, the reversibility of sp 2 -carbon bond formation is poor, making the synthesis of sp 2 -carbon-linked COFs extremely challenging 33 . Since 2016, several examples of sp 2 -carbon COFs have been reported, such as sp 2 c-COF 34 , TP-COF 35 , Por-sp 2 c-COF 33 , and g-C 34 N 6 -COF 36 . However, their application for the detection or extraction of UO 2 2+ has not been explored.…”

A Corrole‐Based Covalent Organic Framework Featuring Desymmetrized Topology

“…At longer wavelengths the spectra of TPAPC‐COF and the solid corrole monomer are nearly identical, indicating similar packing schemes in the COF and solid‐state building block . The optical band gap, based on the absorption onset, is estimated to be 1.06 eV for TPAPC‐COF (Figure S13) . With this small band gap, TPAPC‐COF is an excellent photoactive material, which can efficiently harvest the sunlight energy and even utilize low‐energy photons to generate photoexcited states.…”

“…[22a] The optical band gap, based on the absorption onset, is estimated to be 1.06 eV for TPAPC-COF (Figure S13). [23] With this small band gap, TPAPC-COF is an excellent photoactive material, which can efficiently harvest the sunlight energy and even utilize low-energy photons to generate photoexcited states.…”

Interfacial Synthesis of a Monolayered Fluorescent Two‐Dimensional Polymer through Dynamic Imine Chemistry

“…Two-dimensional polymers (2DPs) have been generally accepted as materials with atomic-thick or monolayer, covalently linked, highly ordered 2D topological network. [1][2][3][4][5][6][7][8] The recent high interest and the fast development of 2DPs materials are driven by their unique structures, [9][10][11] potential applications [12][13][14][15][16] and infinite structure possibilities through monomer design. [17] The properties of the 2DPs are completely different from those of traditional linear or branched polymers due to the total different 2D structure.…”

“…[33][34][35] Nevertheless, the synthesis of the 2DPs is usually challenging, especially the monolayer synthesis. So far, several strategies have been developed such as single crystal to single crystal method, [36][37][38] solution synthesis, [11,39] and interfacial synthesis. [40][41][42][43] Among which the interfacial synthesis method is ideal to obtain ultrathin, large-area, free-standing 2DPs under ambient conditions.…”