Schiff-base molecules and COFs as metal-free catalysts or silver supports for carboxylation of alkynes with CO₂

Abstract

Carboxylating terminal alkynes with CO2 to produce propiolic acids is an atom-economic and high-value route for CO2 fixation and utilization, but the conversion under mild conditions needs transition metal catalysts....

Evolving Trends for C−C Bond Formation Using Functionalized Covalent Organic Frameworks as Heterogeneous Catalysts

“…Carboxylation of terminal alkynes with CO 2 to produce propiolic acids (Scheme 31) was reported in presence of silver immobilized TpBpy based COF [ Ag@TpBpy, Figure 17] by Zhang and co-workers. [125] The activation of CO 2 through phenoxo-CO 2 complexation and the C(sp)-H bond through bifurcate CÀ H⋅⋅⋅N imine and CÀ H⋅⋅⋅O phenoxo hydrogen bonds of the catalyst are reported to help in the reaction. Furthermore, 2,2'-bipyridyl sites present in the COF also contribute to the catalytic performance.…”

“…Although major developments have been achieved in this area during the past decade, key issues like stability, harsh reaction conditions, limited substrate scope in many reactions, average yields and stereoselectivity, leaching, sintering, and recyclability of COF based hybrid materials is still a matter of big concern. Many commercial processes still largely use homogeneous catalysis for CÀ C bond formation reactions, due to their ability to provide non-polar environment essential for producing high Carboxylation of Alkynes Ag@TpBpY 2,2'-bipyridine-5,5'-diamine (Bpyda) and 1,3,5-triformylphloroglucinol (Tp) followed by AgNO 3 [125] Homo-coupling reaction Cu(II)-TRIPTA 2,4,6-Triformylphloroglucinol and 1,3,5-Tris-(4-aminophenyl) triazine [126]…”

Visible Light‐Driven Carboxylation of Olefins by Using 2D Metal‐Free Covalent Organic Framework as Intrinsic Photocatalyst: A Sustainable Approach for CO2 Utilization

“…[46][47][48] In recent times, Chakrabortty et al fabricated TpPa-1 COF showing its photocatalytic activity towards carboxylation of aryl halides via SP 2 CÀ H/X activation. [49] Beside this, Zhang and co-workers recently introduced carboxylation of alkynes using COF-based Ag nanoparticles [50] but there is lack of reports of carboxylation of alkenes using suitable COF as an efficient heterogeneous photocatalyst under metal free condition.Therefore, the development of potential, non-toxic, renewable and transition metal-free organocatalyst is necessary and beneficial for incorporation of CO 2 into unsaturated alkenes under greener pathway, resulting in the formation of carboxylic acids.…”

Bifunctional metal–organic frameworks afforded by postsynthetic modification for efficient cycloaddition of CO2 and epoxides

“…To date, multifarious catalysts, including ionic liquids, functional polymers, metal complexes, various supported catalysts, and most recently metal-organic frameworks (MOFs), were explored in the field of catalysis. [37][38][39][40][41][42][43][44] Among these, MOFs have been regarded as promising heterogeneous catalysts for the cycloaddition of CO 2 to epoxides (CCE), because of their chemical and composition tunabilities, high surface areas, and their permanent porosities. [39][40][41][42] Although an increasing number of MOFs as catalysts with Lewis acid sites have been utilized for CCE, most of them are efficient only with cocatalytic anions such as tetrabutylammonium bromide (TBAB).…”