M2(&ITm&IT-dobdc) (M &DBLBOND; Mn, Fe, Co, Ni) Metal-Organic Frameworks as Highly Selective, High-Capacity Adsorbents for Olefin/Paraffin Separations
M2(&ITm&IT-dobdc) (M &DBLBOND; Mn, Fe, Co, Ni) Metal-Organic Frameworks as Highly Selective, High-Capacity Adsorbents for Olefin/Paraffin Separations
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DOI：
10.1021/jacs.7b06397
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发表时间：
2017-11-01
影响因子：
15
通讯作者：
Long, Jeffrey R.
中科院分区：
文献类型：
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作者：
Bachman, Jonathan E.;Kapelewski, Matthew T.;Long, Jeffrey R.
评价了金属有机骨架M-2(m-DOBDC)(M=Mn，Fe，Co，Ni；m-DOBDC(4-)=4，6-二氧代-1，3-苯二甲酸根)作为分离石蜡中烯烃的吸附剂。用单组分和多组分的平衡气体吸附测量结果表明，这些材料中配位不饱和的M2+位对乙烷和丙烷的物理吸附分离性能优于任何已知的吸附剂，包括对官能化的结构异构体M-2(p-DOBDC)(p-DOBDC(4-)=2，5-二氧代-1，4-苯二甲酸根)。值得注意的是，与相应的结构异构体相比，M-2(m-DOBDC)骨架在烷烃上对烯烃的亲和力都有所增加，其中Fe、Co和Ni变体的选择性增加了一倍以上。在这些骨架中，Fe-2(m-DOBDC)在相应的条件下表现出最高的乙烯/乙烷(>；25)和丙烯/丙烷(>；55)选择性，烯烃容量超过7 mmol/g。通过原位单晶X射线衍射对乙烯在Co-2(m-dobdc)和Co-2(p-dobdc)中的结构表征结合微分热焓计算表明，选择性的显著提高源于金属中心电荷密度的增加引起的金属-烯烃相互作用的增强。乙烯和丙烯的中等烯烃结合热分别低于55和70kJ/mol，表明这些吸附剂在温和的再生条件下保持了足够的可逆性。此外，瞬时吸附实验显示出较快的吸附动力学，90%以上的乙烯吸附发生在给药后30 S内。突破性的测量进一步表明，CO-2(m-DOBDC)可以在没有温度摆动的情况下生产高纯度烯烃，这是对工艺适用性的重要测试。良好的烯烃/烷烃选择性、高的烯烃容量、快速的吸附动力学和低廉的原料成本使M-2(m-DOBDC)骨架成为吸附分离烯烃/烷烃的首选材料。
The metal-organic frameworks M-2(m-dobdc) (M = Mn, Fe, Co, Ni; m-dobdc(4-) = 4,6-dioxido-1,3-benzenedicarboxylate) were evaluated as adsorbents for separating olefins from paraffins. Using single-component and multicomponent equilibrium gas adsorption measurements, we show that the coordinatively unsaturated M2+ sites in these materials lead to superior performance for the physisorptive separation of ethylene from ethane and propylene from propane relative to any known adsorbent, including para-functionalized structural isomers of the type M-2(p-dobdc)(p-dobdc(4-) = 2,5-dioxido-1,4-benzenedicarboxylate). Notably, the M-2(m-dobdc) frameworks all exhibit an increased affinity for olefins over paraffins relative to their corresponding structural isomers, with the Fe, Co, and Ni variants showing more than double the selectivity. Among these frameworks, Fe-2(m-dobdc) displays the highest ethylene/ethane (>25 ) and propylene/propane (>55) selectivity under relevant conditions, together with olefin capacities exceeding 7 mmol/g. Differential enthalpy calculations in conjunction with structural characterization of ethylene binding in Co-2(m-dobdc) and Co-2(p-dobdc) via in situ single-crystal X-ray diffraction reveal that the vast improvement in selectivity arises from enhanced metal-olefin interactions induced by increased charge density at the metal site. Moderate olefin binding enthalpies, below 55 and 70 kJ/mol for ethylene and propylene, respectively, indicate that these adsorbents maintain sufficient reversibility under mild regeneration conditions. Additionally, transient adsorption experiments show fast kinetics, with more than 90% of ethylene adsorption occurring within 30 s after dosing. Breakthrough measurements further indicate that Co-2(m-dobdc) can produce high purity olefins without a temperature swing, an important test of process applicability. The excellent olefin/paraffin selectivity, high olefin capacity, rapid adsorption kinetics, and low raw materials cost make the M-2(m-dobdc) frameworks the materials of choice for adsorptive olefin/paraffin separations.