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Calcium Poly(Heptazine Imide): A Covalent Heptazine Framework for Selective CO2 Adsorption
ACS Nano ( IF 15.8 ) Pub Date : 2022-03-31 , DOI: 10.1021/acsnano.1c08912
James N Burrow 1 , Ryan A Ciufo 2 , Lettie A Smith 2 , Yu Wang 3 , David C Calabro 3 , Graeme Henkelman 2, 4 , C Buddie Mullins 1, 2, 4
Affiliation  

Potassium poly(heptazine imide) (KPHI) has recently garnered attention as a crystalline carbon nitride framework with considerable photoelectrochemical activity. Here, we report a Ca2+-complexed analogue of PHI: calcium poly(heptazine imide) (CaPHI). Despite similar polymer backbone, CaPHI and KPHI exhibit markedly different crystal structures. Spectroscopic, crystallographic, and physisorptive characterization reveal that Ca2+ acts as a structure-directing agent to transform melon-based carbon nitride to crystalline CaPHI with ordered pore channels, extended visible light absorption, and altered band structure as compared to KPHI. Upon acid washing, protons replace Ca2+ atoms in CaPHI to yield H+/CaPHI and enhance porosity without disrupting crystal structure. Further, these proton-exchanged PHI frameworks exhibit large adsorption affinity for CO2 and exceptional performance for selective carbon capture from dilute streams. Compared to a state-of-the-art metal organic framework, UTSA-16, H+/CaPHI exhibits more than twice the selectivity (∼300 vs ∼120) and working capacity (∼1.2 mmol g–1 vs ∼0.5 mmol g–1) for a feed of 4% CO2 (1 bar, 30 °C).

中文翻译:

钙聚(庚嗪酰亚胺):用于选择性 CO2 吸附的共价庚嗪骨架

聚(庚嗪酰亚胺)钾(KPHI)最近作为具有相当大的光电化学活性的结晶氮化碳骨架而受到关注。在这里,我们报告了 PHI 的 Ca 2+络合类似物:聚(庚嗪酰亚胺)钙 (CaPHI)。尽管聚合物主链相似,但 CaPHI 和 KPHI 表现出明显不同的晶体结构。光谱学、晶体学和物理吸附表征表明,与 KPHI 相比,Ca 2+作为结构导向剂将瓜基氮化碳转化为具有有序孔道、扩展可见光吸收和改变能带结构的结晶 CaPHI。酸洗后,质子取代 CaPHI 中的 Ca 2+原子产生 H +/CaPHI 并在不破坏晶体结构的情况下提高孔隙率。此外,这些质子交换的 PHI 骨架对 CO 2表现出较大的吸附亲和力,并且在从稀流中选择性捕获碳方面表现出卓越的性能。与最先进的金属有机骨架 UTSA-16 相比,H + /CaPHI 的选择性(~300 vs ~120)和工作容量(~1.2 mmol g –1 vs ~0.5 mmol g)超过两倍–1 ) 用于 4% CO 2的进料(1 巴,30 °C)。
更新日期:2022-03-31
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