Phenyl Extended Naphthalene‐Based Covalent Triazine Frameworks as Versatile Metal‐Free Heterogeneous Photocatalysts

Abstract

Two new covalent triazines frameworks (CTFs) containing phenyl extended naphthalene units (with and without methoxy groups in the naphthalene core) are prepared by thermal and microwave activation. Both procedures yield similar chemical structures combining triazine acceptor units with donor aromatic groups, but they generate some differences in the morphology, structural organization, CO2 adsorption capacity, and thermal and optical properties. Besides, the methoxy groups of the naphthalene core have also influence in some of these properties. The resulting phenyl extended naphthalene CTFs are efficiently utilized as metal‐free heterogeneous photocatalyst for the selective aerobic oxidation of sulfides and the dehydrogenative cross‐coupling reactions under visible‐light irradiation, showing a high chemical stability.

Recent Advances in the Use of Covalent Organic Frameworks as Heterogenous Photocatalysts in Organic Synthesis

“…In contrast, Iglesias and co‐workers synthesized different amorphous CTFs containing naphthalene units through thermal and microwave‐assisted synthesis, able to generate both singlet oxygen and superoxide radical anion for different photooxidative transformations. [ 159 ] In particular, regarding sulfide oxidation, ten catalytic cycles with full conversion and total selectivity were achieved under blue LED irradiation and air atmosphere. In another example by Wang et al., the dual photoredox‐energy transfer nature of a series of CTFs was also evaluated.…”

“…Interestingly, the catalytic activity and selectivity (against the oxidized PhTHIQ product) of NDP‐CTF were higher than those of the methoxy‐containing NDMDP‐CTF under blue LED light (50 W) ( Scheme ). [ 159 ] However, the reaction with ketones as nucleophiles did not afford the desired product. In this catalytic system, the THIQ‐radical plays a key role and its formation takes place via a proton capture (anaerobic pathway).…”

Hyper-Cross-Linked Porous Polymer Featuring B–N Covalent Bonds (HCP-BNs): A Stable and Efficient Metal-Free Heterogeneous Photocatalyst

“…This model reaction is a very useful tool in organic syntheses to generate C−C bonds and is very extended to evaluate the photocatalytic activity of porous materials. 14,29 The first essays were conducted using 2-phenyl-1,2,3,4tetrahydroisoquinoline (THIQ) as the substrate and nitromethane as a nucleophile, without additional solvent and blue LED as the light source under an air atmosphere (Table 1).…”

“…From the Kubelka−Munk function equation (tauc plot) obtained by the UV−vis diffuse reflectance spectra (Figure S9), a band gap energy of 2.38 eV was obtained, which is a value similar to those reported for conjugated porous polymers 14 and within the interval obtained for efficient photocatalysts recently reported. 29 To gain more insight into the applicability of the BNTpolymer as a photocatalyst, other nucleophiles, such as malonate (entries 7 and 8) and trimethylsilyl cyanide (entries 9 and 10), were tested. In both cases, the target compound was obtained with almost 100% selectivity and full THIQ conversion in the second run.…”

“…The photocatalytic activity of the B–N polymer was evaluated through the aza-Henry cross-coupling reaction (the catalytic experiment’s details and catalytic activity monitoring are given in the SI). This model reaction is a very useful tool in organic syntheses to generate C–C bonds and is very extended to evaluate the photocatalytic activity of porous materials. , The first essays were conducted using 2-phenyl-1,2,3,4-tetrahydroisoquinoline (THIQ) as the substrate and nitromethane as a nucleophile, without additional solvent and blue LED as the light source under an air atmosphere (Table ). After carrying out several experiments varying the amount of catalyst and the reaction time, a catalyst loading of 5 mol % and blue light irradiation for 4 h (entry 1) was established as optimal reaction conditions to carry out this transformation.…”