Two-dimensional semiconducting covalent organic frameworks via condensation at arylmethyl carbon atoms

Abstract

Construction of organic semiconducting materials with in-plane π-conjugated structures and robustness through carbon-carbon bond linkages, alternatively as organic graphene analogs, is extremely desired for powerfully optoelectrical conversion. However, the poor reversibility for sp 2 carbon bond forming reactions makes them unavailable for building high crystalline well-defined organic structures through a self-healing process, such as covalent organic frameworks (COFs). Here we report a scalable solution-processing approach to synthesize a family of two-dimensional (2D) COFs with trans -disubstituted C = C linkages via condensation reaction at arylmethyl carbon atoms on the basis of 3,5-dicyano-2,4,6-trimethylpyridine and linear/trigonal aldehyde (i.e., 4,4″-diformyl- p -terphenyl, 4,4′-diformyl-1,1′-biphenyl, or 1,3,5-tris(4-formylphenyl)benzene) monomers. Such sp 2 carbon-jointed-pyridinyl frameworks, featuring crystalline honeycomb-like structures with high surface areas, enable driving two half-reactions of water splitting separately under visible light irradiation, comparable to graphitic carbon nitride (g-C 3 N 4 ) derivatives.

Transformation between 2D and 3D Covalent Organic Frameworks via Reversible [2 + 2] Cycloaddition

“…[19][20][21] Finally, polymerization in an single-crystal-to-single-crystal manner was achieved successfully via [2+2] cycloaddition using some coordination polymers and metal-organic frameworks. [22][23][24][25][26][27][28][29] In the field of covalent organic frameworks (COFs), [30][31][32][33][34][35][36][37][38][39][40] the only reversible topological reaction reported to date is based on [4+4] cycloaddition from Jiang's group. 41 The packing of their boronate ester-linked 2D COF places the reactive anthracene moieties one on top of another, at a favorable distance of 3.4 Å, such that photoirradiation leads to their dimerization through 9,10-positions, resulting in a 2D COF with twinned layers.…”

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

“…In addition, their weak π-electron delocalization over the framework hinders fluorescence yield 36 . Carbon-carbon double bonds (-C═C-) are more stable and can keep conjugated π-electrons, which can overcome the above challenges 36,41 . In addition, their intrinsic open 1D channels and regular porous structures facilitate exposure of binding sites, boosting rapid diffusion, and mass transfer.…”

Regenerable Covalent Organic Frameworks for Photo‐enhanced Uranium Adsorption from Seawater

“…2218 cm À1 )w as found, indicating that both NDA-TN and BDA-TN were highly condensed. [2c] Their 13 CC P/MAS NMR further confirmed this efficient condensation, as demonstrated by the peak located at about 106 ppm ascribed to the carbon atoms in the cyano groups (Supporting Information, Figures S5, S6). [2c] To evaluate the crystallinity of NDA-TN and BDA-TN, PXRD was performed (Figure 3a,b).…”

“…Recently,e fforts have been devoted to construct stable semiconductor sp 2 -carbon COFs synthesized by the Knoevenagel condensation approach, such as TFPT-BTAN, [2c] sp 2 c-COF, [11] Por-sp 2 c-COF, [12] and g-C 40 N 3 -COF. [13] Benefiting from the highly stable C=Cb onds,t he sp 2 -carbon-linked COFs showed excellent stability even under harsh conditions such as strong radiation, acids,b ases,a nd saturated NaCl solutions.F urthermore,t he fully extended p-conjugation of C = Cl inkage endowed the sp 2 -carbon-linked COFs highly conjugated p-electrons and good semiconductor properties, [14] which can effectively promote photocatalysis and photoelectric activities.…”