Nanoporous azo polymers (NAPs) for selective CO2 uptake.

Graphical abstract Highlights • Facile synthesis of nanoporous azo polymers (NAPs) using metal-catalyst free polycondensations in basic medium. • NAPs have been designed to include triptycene, phorphyrin and azo units in the polymer backbone. • NAPs exhibits high surface area up to 1095 m² g⁻¹. • High CO 2 uptake up to 3.93 mmol g⁻¹ at 273 K and 1 bar uptake by these NAPs. • Good CO 2 /N 2 selectivity (up to 64 at 273 K) shown by these NAPs. Abstract Two nanoporous azo polymers (NAPs) have been designed incorporating triptycene and porphyrin motifs in the polymer framework that are linked covalently by azo functional groups. NAPs are synthesized using metal-catalyst free polycondensations in basic medium. These are thermally stable, microporous (Type-I isotherms in N 2 adsorption–desorption measurements at 77 K) and have moderately high surface areas (SA BET = 1095 and 923 m² g⁻¹). NAPs show enhanced surface areas relative to either triptycene networks with azo-linkages or porphyrinic polymers having azo bridges. NAPs register high CO 2 uptake (upto 3.93 mmol g⁻¹ at 1 bar and 273 K) with good CO 2 /N 2 selectivity (upto 64:1 at 273 K) for CO 2 capture from flue gas. Incorporation of CO 2 -philic porphyrin rings and N 2 -phobic azo groups results in improved CO 2 /N 2 selectivity in these triptycene based microporous polymers. Performance of NAPs as nanoporous polymer (in terms of gas sorption properties such as surface areas, low pressure gas uptake and gas selectivity) is also better than several non-triptycene/porphyrin but azo based porous organic polymers (POPs). NAPs have potential use in post-combustion CO 2 capture and sequestration technology. [ABSTRACT FROM AUTHOR]