We systematically investigate dynamic separation of Xe and Kr at room temperature using four representative porous materials(Cu-BTC, ZIF-8, COP-4 and activated carbon(AC)). Results indicate that among the four materials, Cu-BTC not only shows the highest retention volume per gram(V_g=788 m L g^(-1), which is 1.8 times of activated carbon(436 m L g^(-1))) under flowing condition, but also can separate 350 ppm Xe from 35 ppm Kr mixture in air with a high Xe/Kr selectivity of 8.6 at room temperature and 200 k Pa, due to its suitable pore morphology, open metal sites, small side pockets in the framework. Moreover, the Cu-BTC also performs well on individual separation of Xe, Kr, CO_2 from five-component gas mixture(Xe:Kr:CO_2:Ar:N_2= 1:1:1:1:0.5, V/V) and has the longest retention time for Xe(20 min) in gas chromatographic separation, suggesting that it is a good candidate for potential applications as polymeric sieves.
Qian WanShunshun XiongZhonghua XiangShuming PengXiaolin WangDapeng Cao
傅里叶变换红外(FT-IR)光谱、表面压力-分子面积(π-A)等温线和原子力显微镜(AFM)结果表明,聚乙烯吡咯烷酮(PVP)与胆固醇分子(Chol)在溶液中和气/液界面上可通过氢键作用形成刷状的超分子聚合物PVP-Chol。当表面压力低于2.5 m N?m^(-1)时,界面膜主要由富含胆固醇的微区与PVP-Chol纳米纤维构成的微区共存。在相对较低的表面压力下(<2.5 m N?m^(-1)),PVP-Chol微区形貌随界面膜压缩发生有序的变化:从最初的无规结构逐渐变为月牙形、心形和圆形结构;表面压超过2.5 m N?m^(-1)后,圆形的PVP-Chol微区最终消失并转变为少量的纤维聚集体结构。值得注意的是,在1.0 m N?m^(-1)之前,PVP-Chol纳米纤维高度随AFM成像过程中压电陶瓷外加电压的变化在1.8到4.3 nm之间出现了可逆转变,表明扫描探针针尖与样品之间的作用力可诱导超分子聚合物刷PVP-Chol发生从圆柱状到椭柱状的可逆结构转变。
The toxic gases,such as CO and NO,are highly dangerous to human health and even cause the death of person and animals in a tiny amount.Therefore,it is very necessary to develop the toxic gas sensors that can instantly monitor these gases.In this work,we have used the first-principles calculations to investigate adsorption of gases on defective graphene nanosheets to seek a suitable material for CO sensing.Result indicates that the vancancy graphene can not selectivly sense CO from air,because O2 in air would disturb the sensing signals of graphene for CO,while the nitrogen-doped graphene is an excellent candidate for selectivly sensing CO from air,because only CO can be chemisorbed on the pyridinic-like N-doped graphene accompanying with a large charge transfer,which can serve as a useful electronic signal for CO sensing.Even in the environment with NO,the N-doped graphene can also detect CO selectively.Therefore,the N-doped graphene is an excellent material for selectively sensing CO,which provides useful information for the design and fabrication of the CO sensors.
Two porous organic polymer nanotubes(PNT-2 and PNT-3) were synthesized via Ni-catalyzed Yamamoto reaction, using2,4,6-tris-(4-bromo-phenyl)-[1,3,5]-triazine(TBT) as one monomer, and 2,7-dibromopyrene(DBP) or 1,3,6,8-tetrabromopyrene(TBP) as another monomer. The scanning electron microscope(SEM) images show that both PNT-2 and PNT-3 possess clear hollow tube structures. Luminescent measurements indicate that both PNT-2 and PNT-3 can serve as luminescent probe for highly selective and sensitive detection of Fe^(3+) by luminescent quenching effect. Absorption competition quenching(ACQ) mechanism is also proposed to explain luminescent quenching behavior, i.e., the overlap of the UV-spectra between Fe^(3+) and PNTs causes the energy competition, and therefore leads to luminescent quenching. Moreover, both PNT-2 and PNT-3 still show high selectivity and sensitivity for sensing Fe^(3+) in 10% ethanol aqueous solution, which means that the two porous PNTs are promising candidates as luminescent probes for detecting Fe^(3+) in practical applications.
