Topology-directed design and synthesis of carbazole-based conjugated microporous networks for gas storage

Abstract

Two topological-directed conjugated microporous networks, P-TPATCz and P-CzPTCz, have been synthesized. The two initial building blocks have a similar chemical constitution but different geometrical configuration (TPATCz: quasi-tetrahedron 3D and CzPTCz: quasi-coplanar 2D structure). Scanning electron microscopy and powder X-ray diffraction indicated that the quasi-tetrahedron structure monomer TPATCz is facile to form columnar crystalline aggregation, whereas the quasi-coplanar monomer of CzPTCz forms amorphous aggregation networks. Thermogravimetric analysis showed that the thermal stability of two networks at high temperature may be affected by the stability of the core in the building blocks. Changing the triphenylamine core of monomer TPATCz to 9-phenyl-9H-carbazole in CzPTCz resulted in an increase in the Brunauer–Emmett–Teller surface area of P-TPATCz (337 m² g⁻¹) to 1315 m² g⁻¹ for P-CzPTCz. The hydrogen isotherms of P-TPATCz and P-CzPTCz showed H₂ storage up to 0.85 and 1.90 wt% at 77 K/1.1 bar, respectively. At 273 K/1.1 bar, the CO₂ uptake capacity of P-CzPTCz was up to 17.0 wt%, which is 5.8 times than that of P-TPATCz. Fine designing and tailoring of the steric configuration of the building block can pre-determine the physicochemical property of the target networks and influence the gas uptake performance.