Synthesis And Gas Storage Properties Of Porous Aromatic Frameworks

Microporous materials have been proved to have the potential application in gas storage and separation by physical adsorption during last decades. Such application usually based on the presence of a large permanent surface area and suitable enthalpy of adsorption between micropore and gas molecules. In last decades, a series of POFs such as metal-organic frameworks (MOFs), covalent organic frameworks (COFs), polymers of intrinsic microporosity (PIMs), conjugated microporous polymers (CMPs), hyper crosslinked polymers (HCPs), crystalline triazine-based organic frameworks (CTFs) and porous aromatic frameworks (PAFs) have been prepared. PAF-1 (poly(4-tetraphenylene)methane) exhibit ultrahigh surface area and high physicochemical stability, in addition, it shows high uptakes of H2 (7.0 wt% excess at 77 K/48 bar) and CO2 (1.3 g g-1 at 40 bar,298 K).Herein, we design and synthesis of poly(4-tetraphenylene)silane (PAF-3) and poly(4-tetraphenylene)germane (PAF-4) with dia topology the same with PAF-1 via Yamamoto-type Ullmann reaction. As PAF-1 (SBET= 5460 m2g-1), PAF-3 (SBET=2293 m2g-1) and PAF-4 (SBET=2246 m2g-1) exhibit big surface areas and high physicochemical stability. The H2 (PAF-3:QstH2=6.6 kJmol-1; PAF-4:QstH2=6.3 kJmol-1), CO2 (PAF-3:QstCO2=19.2 kJmol-1; PAF-4:QstCO2=16.3 kJmol-1), CH4 (PAF-3:QstCH4=15.0 kJmol-1; PAF-4:QstCH4=23.2 kJmol-1) heat of adsorption of PAF-3 and PAF-4 is bigger than that of PAF-1 due to the quaternary Si or Ge in skeletons respectively, while the uptake capacity of PAF-3 and PAF-4 is even higher than that of PAF-1 in low pressure range. To further investigate the parameter of adsorption, we design and synthesis of another polymer polytri(4-phenyl)silanol (JUC-Z3) which contains biphenyl group connected the Si tetrahedrol center and hydroxyl functional group in the framework. The result from gas sorption measurements exhibit that hydroxyl group in JUC-Z3 structure can effectively reinforce the interaction between adsrobate and adsorbent, even higher than that of PAF-3, which show potential application in energy field.