Nitrogen Coordination To Dramatically Enhance the Stability of In-MOF for Selectively Capturing CO₂ from a CO₂/N₂ Mixture

Abstract

Two In-based metal−organic frameworks (MOFs) have been designed and synthesized by the reaction of 3phenylpyridine polycarboxylic ligands and In 3+ cations: In 3 L 1 4 •(CH 3 NH 2 CH 3 ) 3 (H 3 L 1 = 5-(3′,5′-dicarboxylphenyl)nicotic acid; 1) and In 2 L 2 2 (CH 3 COO) 2 •(CH 3 ) 2 NH 2 •(CH 3 ) 3 NH•H 2 O (H 3 L 2 = 3-(2,4-dicarboxylphenyl)-6-carboxylpyridine;2). Singlecrystal X-ray diffraction analysis indicates that the In 3+ centers in 1 are all coordinated by eight oxygen atoms from four carboxylate groups, resulting in a 3D framework with two different channels A and B with sizes of 14.4 × 8.75 and 7.24 × 6.7 Å 2 , respectively. In 2, each In 3+ center was coordinated by six carboxylate oxygen atoms and a pyridine N atom, forming a 2D layerlike structure. These 2D layers are further fused together via electrostatic interactions into a 3D supramolecular framework, showing two kinds of channels A′ and B′ with pore sizes of 5.25 × 9.69 and 4.29 × 8.66 Å 2 , respectively. In this work, the coordination of N to the In 3+ center in 2 was first achieved by regulating carboxyl sites in 3-phenylpyridine, thus increasing the stability of the In-based MOF. A detailed structural study reveals that the formation of In−N bonds promotes the conversion of the 3D framework of 1 into the supramolecular structure of 2. However, the supramolecular structure in 2 is more stable in air and methanol in comparison to the 3D framework of 1, confirming the important role of In−N bonds in enhancing the framework stability. Thus, 2 could be used as a stable adsorbent to selectively capture CO 2 from a CO 2 /N 2 mixture, while 1 broke down sharply in air and in a methanol solution.

Porous Metal–Organic Frameworks for Carbon Dioxide Adsorption and Separation at Low Pressure

“…Moreover, the residual M could effectively prevent the interaction between N 2 and frameworks . Furthermore, Zhang et al built an In-based MOFs (In 3 L 1 159 4 ·(CH 3 NH 2 CH 3 ) 3 ) via 5-(3′,5′-dicarboxylphenyl)­nicotic acid (H 3 L 1 159 ) (Figure ). In this structure, a per In 3+ ion was coordinated with eight oxygen atoms from four carboxylate groups, which formed two different channels with the sizes of 14.4 Å × 8.75 Å and 7.24 Å× 6.7 Å.…”

“…Structures of H 3 L 1 159 and H 3 L 2 159 with different positions of carboxyl groups. Reprinted with permission from Peng et al, American Chemical Society, Copyright 2019.…”

“…Moreover, the residual M could effectively prevent the interaction between N 2 and frameworks. 158 Furthermore, Zhang et al 159 160 assembled Ni-4Pyc via Ni 2+ and pyridine-4-carboxylic acid (4Pyc) with a ultramicropore of 6.8 Å. It was worth noting that the ultramicropore (<0.7 nm) was beneficial to CO 2 capture.…”

Large-Scale Screening and Machine Learning to Predict the Computation-Ready, Experimental Metal-Organic Frameworks for CO2 Capture from Air

“…To date, thousands of MOFs have been synthesized, some of which have been utilized in the attempt to capture CO 2 from the air. Peng et al [28] designed and synthesized 2 incorporated MOFs to study their stability and ability to capture CO 2 from the air. Liu et al [11] used an amine-functionalized MOF and an ultra-microporous MOF to capture CO 2 directly from the air, and further investigated the performance of CO 2 capture and the reproducibility of MOFs under humid conditions.…”

A Multi-Functional In(III)-Organic Framework for Acetylene Separation, Carbon Dioxide Utilization, and Antibiotic Detection in Water

“…Metal–organic frameworks (MOFs) have been extensively used as porous materials in many fields due to the advantages of combining organic and inorganic materials, as well as due to their adjustable structures and functional pore environment. − Although a large number of research studies have shown potential application prospects of MOFs, their practical application undergoes some challenges, such as their typically poor stability, especially in water. , Recent advances have confirmed the success of using carboxylate-N-heterocyclic ring ligands to construct stable MOFs in which the rich-N azolate groups not only provide potential basic sites but also form rigid coordination bonds and where carboxylate units possess flexible coordinated modes . Besides this, metal ions are also important in the construction of stable MOFs; the high-oxidation-state Zr 4+ , Ti 4+ Cr 3+ , Fe 3+ , Al 3+ , and In 3+ ions can easily generate MOFs that are stable in acid, base, and water. − The In-MOFs are especially interesting and important because In 3+ ions can form various building blocks including {InO/OH} clusters and infinite chain units, producing versatile stable frameworks. ,− According to the hard–soft acid–base (HSAB) theory, most In 3+ ions tend to coordinate with the carboxylic acid oxygen atoms to form In-based 2D and 3D MOFs. ,− However, recent studies have found that In–N bonds are very favorable to generate stable MOFs, , but the design and synthesis of In-MOF materials containing In–N bonds are still in their infancy.…”