Visible Light-Driven C(sp³)-H Carboxylation of Diverse Amines with CO₂ into α-Amino Acids Using an Eco-Friendly and Reusable Covalent Organic Framework

Abstract

Direct photochemical carboxylation of C(sp3)–H bonds with CO2 is an uphill task and it has attracted increasing attention. In the present study, we report an elegant strategy for visible-light-triggered C(sp3)-H carboxylation of amines with CO2 into α-amino acids using a stable crystalline polyimide-based covalent organic framework (PI-COF) as an efficient heterogeneous photocatalyst and NiO nanoparticles (NiO NPs) as a cocatalyst under ambient conditions (room temperature and atmospheric CO2 pressure). Diverse amino acids are produced in moderate-to-high yields. This methodology tolerates a range of functional groups and displays remarkable regioselectivity. Various drugs were effectively achieved using this light-assisted approach. The high chemical stability of the COF and its strong interactions with NiO NPs renders the catalytic system to be highly recyclable (i.e., over five times). More interestingly, this photoinduced carboxylation reaction occurred without the involvement of any sacrificial electron donors. Based on computational (DFT) investigations, a tentative mechanism revealed the formation of CO2 radical anion at the conduction band (CB) of the COF via single electron transfer mediated by NiO nanoparticles which combined with amine radical cation at the valence band of the COF to form α-amino acid.

Light-Mediated Sustainable Conversion of Carbon Dioxide to Valuable Methanol by Highly Efficient Covalent Organic Framework g-C3N4 Composites as a Reusable Photocatalyst

“…Four different peaks with binding energies of 284.8, 285.7, 286.7, and 288.4 eV were present in the high-resolution XPS C 1s spectra and were associated with the C−C/C�C bond, C−N bond, C�N−C fragment, and N−C�N fragment, respectively (Figure 14a). While the N 1s peak observed at around 399.5 eV results from the N−NiO interaction and N− C bond, the peak at 398.9 eV in the N 1s spectra indicates sp 2hybridized N�C bonds 122 in the triazine ring (Figure 14b).…”

Visible Light-Driven Flexible Synthesis of α-Alkylated Glycine Derivatives Catalyzed by Reusable Covalent Organic Frameworks

“…Photoactive covalent organic frameworks (COFs), possessing long π-conjugated systems, highly ordered layer structures, and considerable stability, have become a qualified heterogeneous photocatalyst for visible light-driven organic transformations, featuring additional sustainability and workup simplicity of these processes. − Various functional organic monomers bestow unlimited design ability on photoactive COFs, extending their catalytic power to various visible light-driven organic processes. , To date, many organic reactions, including oxidation, − reduction, , radical cyclization, − C–H bond functionalization, − E – Z isomerization, and cross-coupling, − were compatible with photoactive COFs, proceeding elegantly and fruitfully under visible light irradiation. COFs always played the following three primary roles in the above catalytic cycles.…”

Sunlight induced efficient photocatalytic oxidation of benzylamines and CO2 reduction over a 2D–2D MoS2/FP-BTA heterojunction catalyst

“…Since CO 2 is highly available, economic, non-flammable, renewable, and non-toxic, it has received a lot of attention and has been employed in a variety of organic transformations. 14–16 A very intriguing ecological synthesis method uses CO 2 as a sustainable C1 feedstock in photocatalytic CO 2 fixation or reduction reactions. 17,18 Due to thermodynamic restrictions and the energy demands of CO 2 , most chemical pathways for CO 2 usage are currently in the stage of development and may require some time to implement.…”