Confinement effects on the structure and reactivity of encapsulated buckybowls in cycloparaphenylene.

We theoretically investigated the host-guest chemistry between belt-like cycloparaphenylenes (CPPs) and entrapped bowl-shaped sumanene and corannulene. Density functional theory calculations show that the buckybowls can be stabilized in a CPP host with an appropriately sized cavity (e.g., [10]CPP) through multi-site CH-π interactions. Arising from the confined intermolecular interactions within the cavity, the restrictive buckybowls display novel reactivity distinct from that in their free state.

The meso-substituent electronic effect of Fe porphyrins on the electrocatalytic CO2 reduction reaction.

We report Fe porphyrins bearing different meso-substituents for the electrocatalytic CO2 reduction reaction (CO2RR). By replacing two and four meso-phenyl groups of Fe tetraphenylporphyrin (FeTPP) with strong electron-withdrawing pentafluorophenyl groups, we synthesized FeF10TPP and FeF20TPP, respectively. We showed that FeTPP and FeF10TPP are active and selective for CO2-to-CO conversion in dimethylformamide with the former being more active, but FeF20TPP catalyzes hydrogen evolution rather than the CO2RR under the same conditions. Experimental and theoretical studies revealed that with more electron-withdrawing meso-substituents, the Fe center becomes electron-deficient and it becomes difficult for it to bind a CO2 molecule in its formal Fe0 state. This work is significant to illustrate the electronic effects of catalysts on binding and activating CO2 molecules and provide fundamental knowledge for the design of new CO2RR catalysts.

Defective hBN-Supported Fe2N Single Cluster Catalyst for Active and Selective Electro-Reduction of Multiple CO to Propane: Theoretical Elucidation of Metal-Nonmetal Synergic Effects.

The present work introduces the multiple CO reduction toward C3 products promoted by a newly designed single cluster catalyst consisting of defective hBN and embedded dimerized Fe, by means of density functional theory calculations. We find the strong metal-support interactions give rise to the local strain and electron accumulation of the N coordinated with two metals and resultantly form a Fe2N active center. The metal-nonmetal synergic effect facilitates the coadsorption and C-C coupling of triple CO molecules and finally generates propane in a highly active and selective way.