Porous organic frameworks (POFs), with their excellent performance in catalysis, electricity, sensor, gas storage, and separation, have attracted a great deal of attention from researchers all over the world. Generally, the monomers of POF materials require a rigid three-dimensional molecule configuration together with special functional groups, as well as being triggered by noble metal catalysts. Here we report a low-cost and easy-construction strategy for synthesizing PAF materials. A series of flat multi-benzene compounds are selected as building units, and those phenyl rings could couple together to form polymeric skeletons. The BET surface areas of resulting PAFs are moderate, ranging from 777 to 972 m2 g–1. However, they unexpectedly exhibit superior gas sorption capacities. At 1.0 bar and 77 K, the H2 uptake of PAF-48 reaches 215 cm3 g–1. In addition, PAF-49 shows excellent performance in carbon dioxide and methane sorption, with values of 104 and 35 cm3 g–1, respectively. With those adsorption properties, these PAF materials could be considered as potential candidates for energetic gas adsorbents.Keywords: commercial monomers; gas adsorption; low-cost catalysts; porous organic framework; Scholl reaction; sole phenyl skeleton

Two porous aromatic frameworks, PAF-36 and PAF-37, containing azo moieties, were synthesized via Sonogashira-Hagihara coupling reactions. Gas sorption measurements indicated that reversible stimuli-responsive adsorption properties were triggered by ultraviolet (UV) irradiation and heat treatment, because of the presence of azo functional groups. The initial Brunauer-Emmett-Teller (BET) surface areas of PAF-36 and PAF-37 were 325 and 443 m2 g−1, respectively. After UV irradiation, the BET surface areas increased during the trans-cis isomerization process, and the micropore sizes, around 6 and 8 Å, also increased. In addition, the CO2 adsorption capacities increased slightly because of trans-cis conversion of azo groups. It is worth mentioning that the CO2 uptakes of the polymers were almost constant during multiple cycles of alternating external stimuli, displaying high switchability of the trans-cis isomerization.本文报导了通过Sonogashira-Hagihara反应制备两种骨架含有偶氮官能团的多孔芳香骨架材料, PAF-36和PAF-37, 并研究了它们的氮气及二氧化碳吸附性能. 偶氮官能团经过紫外光照射和加热可以实现顺式和反式结构变换. 它们初始BET比表面积分别是325 m2 g−1和443 m2 g−1. 经过紫外光照, 偶氮官能团发生顺反异构化, 材料的BET比表面积以及在6 Å和8 Å的孔径分布均有所增大. 另外, 紫外光照后, 材料的CO2吸附性能也有一定提高. 对样品进行了三次紫外/加热循环实验后, 样品CO2吸附量几乎保持不变, 表明材料中可以发生顺反异构化的偶氮基团具有高效的开关性能. 在多孔材料中引入光控基团, 可以有效改变材料的孔结构, 进而影响材料的气体分子吸附性能.

We report here the synthesis and carbon dioxide capture of a series of porous aromatic framework (PAF) materials assembled using tri(4-ethynylphenyl)amine and various aryl halides via Sonogashira–Hagihara coupling reactions. These PAF materials show moderate surface areas ranging from 370 m2 g−1 to 953 m2 g−1. The functional groups, such as –COOH, –NH2 and –OH, are incorporated into the backbone of the PAF materials. The isosteric heats of CO2 and CO2/N2 selectivities for these PAFs are calculated based on the CO2 and N2 adsorption isotherms measured at 273 and 298 K. It is found that the –NH2 functionalized network shows the highest isosteric heat of CO2 and CO2/N2 selectivity. In addition, the –COOH functionalized network displays the highest CO2 uptake in terms of per unit areas (4.37 μmol m−2, 273 K). The results indicate the incorporation of functional groups is effective for synthesizing CO2-philic PAF networks with enhanced interaction with CO2 molecules.