Dual‐Function Fluorescent Covalent Organic Frameworks: HCl Sensing and Photocatalytic H₂ Evolution from Water

Abstract

Two ultrastable luminescent covalent organic frameworks (COFs), PyTA‐BC and PyTA‐BC‐Ph, are synthesized through polycondensations of 4,4′,4″,4′″‐pyrene‐1,3,6,8‐tetrayl)tetraaniline (PyTA‐4NH2) with two carbazole‐based derivatives having different degrees of conjugation. The PyTA‐BC and PyTA‐BC‐Ph COFs exhibit ultrahigh thermal stabilities (up to 421 °C), excellent crystallinity, and high Brunauer–Emmett–Teller surface areas (up to 1445 m2 g−1). These COFs display strong fluorescence emissions in various solvents, with their emission maxima gradually red‐shifting upon increasing the polarity of the solvent (solvatochromism). Upon exposure to HCl, they respond very rapidly and sensitively in terms of changing their colors and fluorescence emission maxima. In the presence of a sacrificial electron donor, these COFs mediate the highly efficient photocatalytic evolution of H2 from water. In the absence of a noble metal cocatalyst, the COFs and ascorbic acid provide a photocatalytic H2 production of up to 1183 µmol g−1 h−1 (λ ≥ 420 nm); this value is the highest reported to date for a COF. Such COFs appear to be potentially useful as chemosensors for the naked‐eye and sensitive spectroscopic detection of HCl and as cocatalysts for the sustainable photocatalytic production of H2 from water.

Multifunctional Polyhedral Oligomeric Silsesquioxane (POSS) Based Hybrid Porous Materials for CO2 Uptake and Iodine Adsorption

“…The preparation of porous organic polymers (POPs) has become a hot topic in the academic and industry fields due to their interesting features, such as high physicochemical stability, porous character, low density, facile preparation, low regeneration energy, and good thermal and chemical stabilities [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 ]. Porous organic polymers have been applied in different applications such as light harvesting, chemical sensors, catalysis, iodine uptake, H 2 production from water, water treatment, optoelectronic devices, carbon dioxide reduction, nanofiltration, enantioseparation, energy storage, gas separation, and adsorption [ 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 ]. The synthesis of POPs was successfully achieved using various synthetic methods, including Friedel–Crafts arylation, Schiff base reactions, Suzuki reactions, Yamamoto reactions, Heck reactions, and Sonogashira reactions [ 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 ].…”

Photocatalyst Z-scheme system composed of a linear conjugated polymer and BiVO4 for overall water splitting under visible light

“…5 Conceptually, direct hydrogen production using photocatalyst suspensions is the simplest water-splitting approach in technological terms and it is potentially amenable to large-scale deployment. [7][8][9][10][11][12][13][14][15][16][17] Recently, several examples of photocatalysis has been reported as a one-step overall water splitting. [18][19][20] However, recombination of electron-hole pairs tends to decrease the photocatalytic reaction efficiency.…”

Photocatalysts Based on Organic Semiconductors with Tunable Energy Levels for Solar Fuel Applications

“…[123] Other COFs have further demonstrated the importance of planarity for improving crystallinity and photocatalytic activity. [126] Imine linkages are common in COFs but are susceptible to hydrolysis. [127][128][129] 1,3,5-Triformylphloroglucinol is widely utilized as a trifunctional building block, which undergoes condensation with aromatic diamines followed by irreversible tautomerization to produce stable β-ketoenamine hexagonal COFs.…”

“…[ 123 ] Other COFs have further demonstrated the importance of planarity for improving crystallinity and photocatalytic activity. [ 126 ]…”