N‑Heterocyclic Carbene Moiety
in Highly Porous Organic Hollow Nanofibers for Efficient CO2 Conversions: A Comparative Experimental and Theoretical Study
posted on 2024-01-02, 13:06authored bySudip Bhattacharjee, Anjana Tripathi, Rupak Chatterjee, Ranjit Thapa, Thomas E. Mueller, Asim Bhaumik
Global warming and climate change are two severe environmental
dangers brought on by the steady rise in the carbon dioxide (CO2) concentration in the atmosphere. Thus, in order to reduce
this problem, it is essential to find an efficient material for high
CO2 capture that can simultaneously exhibit good catalytic
activity for CO2 utilization into useful chemicals. Herein,
we report the synthesis of N-heterocyclic carbene-based porous organic
polymers (NHC-01 and NHC-02) using the Friedel–Crafts
reaction with the imidazolium salt and bi-phenyl. Among the two porous
polymers, NHC-01 exhibited outstanding stability, high
flexibility, and high BET surface area (1298 m2 g–1). NHC-01 material displayed a high CO2 uptake
capacity of 2.85 mmol g–1 under 1.0 bar pressure
at 273 K. NHC-01/02 has been utilized as a metal-free
organocatalyst for the CO2 conversion reaction due to its
high surface area, high CO2 absorption capacity, and as
it bears the NHC moiety in the organic network. NHC-01 selectively reduced CO2 to methanol via hydrosilylation
with complete conversion of silane under atmospheric CO2 pressure. Furthermore, the catalyst also shows good catalytic activity
toward N-formylation and reductive cyclization reactions,
which showed good yields up to at least four catalytic cycles. The
reaction mechanisms are also studied by theoretical simulation using
density functional theory (DFT), which shows that intermediates have
the appropriate free energy level for the catalyst to promote the
reaction with a low energy barrier.