Photocatalytic Carboxylation of Terminal Alkynes with CO 2 over Metal–Porphyrin Framework Nanosheets

To develop an environmentally benign and efficient route for converting CO 2 into value-added chemicals is of great importance. Here, we demonstrate the photocatalytic carboxylation of terminal alkynes with CO 2 at room temperature and atmospheric pressure, by copper-based porphyrinic framework photocatalysts Cu 2 TCPP( M ) (TCPP = 5,10,15,20-tetrakis(4-carboxyphenyl)porphyrin; M = Fe, Co, Ni, Cu). The Cu 2 TCPP(Cu) nanosheets (with a small thickness of ∼5.1 nm) exhibit an extremely high performance for the reaction of 1-ethynylbenzene with CO 2 to produce 3-phenylpropiolic acid. The turnover frequency is up to 3.33 mmol g –1 h –1 at 10 h, which is much higher than those of the photothermally and thermally driven routes that are usually adopted for the carboxylation reactions catalyzed by metal–organic frameworks. The mechanism for the superior activity of Cu 2 TCPP(Cu) nanosheets was investigated by a series of experiments and theoretical calculations. It is revealed that the Cu 2 TCPP(Cu) nanosheets not only possess good photoelectronic properties but have desired molecular structure for boosting CO 2 activation, alkyne activation, and carboxylation reactions.