CALF-20 中的湿度响应多态性：用于 CO2 捕获的弹性 MOF 物理吸附剂,ACS Materials Letters

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CALF-20 中的湿度响应多态性：用于 CO2 捕获的弹性 MOF 物理吸附剂
ACS Materials Letters ( IF 9.6 ) Pub Date : 2023-10-05 , DOI: 10.1021/acsmaterialslett.3c00930
Zhihengyu Chen ₁ , Ching-Hwa Ho ₂ , Xiaoliang Wang ₃ , Simon M. Vornholt ₁ , Thomas M. Rayder ₃ , Timur Islamoglu ₃ , Omar K. Farha ₃ , Francesco Paesani ₂ , Karena W. Chapman ₁

Affiliation

CALF-20是一种基于草酸锌的金属有机框架（MOF），具有选择性CO _{2物理吸附作用，这使其在CO}₂捕获方面的潜在应用具有吸引力。然而，为了实现此类应用，CALF-20 结构必须承受长期暴露于环境条件下，这可能会导致结构、化学性质以及性能的变化。在这里，我们发现最初报道的 CALF-20 相（现在表示为 α-CALF-20）在暴露于潮湿环境后经历结构转变，生成新的多晶型物 β-CALF-20，在此通过组合同步加速器粉末 X 射线进行鉴定衍射和对分布函数 (PDF) 分析。这种 α 到 β 的转变是完全可逆的，通过在干燥空气或真空下处理 β-CALF-20 可以再生 α-CALF-20。在与测量气体吸附等温线相关的条件下，β- 快速回复为α-CALF-20 需要通过计算评估β-CALF-20 的CO _{2吸附特性。}β-CALF-20 吸附行为的实验评估并不实用。这些分析表明β-CALF-20比α-CALF-20具有更高的CO ₂吸附热，这可能有利于低分压下的CO _{2吸附选择性。}

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Humidity-Responsive Polymorphism in CALF-20: A Resilient MOF Physisorbent for CO2 Capture

CALF-20 is a zinc-triazole-oxalate-based metal–organic framework (MOF) that exhibits selective CO₂ physisorption, which makes it attractive for potential applications in CO₂ capture. However, to implement such applications, the CALF-20 structure must endure extended exposure to environmental conditions that may lead to changes in structure, chemistry, and, hence, performance. Here we find that the originally reported CALF-20 phase (now denoted α-CALF-20) undergoes a structure transformation following exposure to humid environments to generate a new polymorph, β-CALF-20, identified here through combined synchrotron powder X-ray diffraction and pair distribution function (PDF) analysis. This α-to-β transformation is fully reversible with α-CALF-20 being regenerated by treating β-CALF-20 under dry air or vacuum. The rapid reversion of β- to α-CALF-20 under conditions relevant to measuring the gas adsorption isotherm required the CO₂ adsorption properties for β-CALF-20 to be evaluated computationally. Experimental evaluation of the adsorption behavior of β-CALF-20 is not practical. These analyses suggest that β-CALF-20 has a higher CO₂ heat of adsorption than α-CALF-20, which may be advantageous to CO₂ sorption selectivity at low partial pressures.

更新日期：2023-10-05

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