Ajayan Pooja, Wang Wei, Chen Yichong, Bu Xianhui, Feng Pingyun
Department of Chemistry, University of California, Riverside, California, 92521, United States.
Department of Chemistry and Biochemistry, California State University, Long Beach, California, 90840, United States.
Adv Mater. 2024 Oct;36(41):e2408042. doi: 10.1002/adma.202408042. Epub 2024 Aug 15.
Isoreticular chemistry, which enables property optimization by changing compositions without changing topology, is a powerful synthetic strategy. One of the biggest challenges facing isoreticular chemistry is to extend it to ligands with strongly coordinating substituent groups such as unbound -COOH, because competitive interactions between such groups and metal ions can derail isoreticular chemistry. It is even more challenging to have an isoreticular series of carboxyl-functionalized MOFs capable of encompassing chemically disparate metal ions. Here, with the simultaneous introduction of carboxyl functionalization and pore space partition, a family of carboxyl-functionalized materials is developed in diverse compositions from homometallic Cr and Ni to heterometallic Co/V, Ni/V, Co/In, Co/Ni. Cr-MOFs remain highly crystalline in boiling water. Unprecedentedly, one Cr-MOF can withstand the treatment cycle with 10m NaOH and 12m HCl, allowing reversible inter-conversion between unbound -COOH acid form and -COO base form. These materials exhibit excellent sorption properties such as high uptake capacity for CO (100.2 cm g) and hydrocarbon gases (e.g., 142.1 cm g for CH, 110.5 cm g for CH) at 1 bar and 298K, high benzene/cyclohexane selectivity (up to ≈40), and promising separation performance for gas mixtures such as CH/CO and CH/CH.
同网状化学是一种强大的合成策略，它能够通过改变组成而不改变拓扑结构来优化性能。同网状化学面临的最大挑战之一是将其扩展到具有强配位取代基的配体，如游离的 -COOH，因为这些基团与金属离子之间的竞争性相互作用会破坏同网状化学。拥有一系列能够包含化学性质不同的金属离子的羧基官能化金属有机框架（MOF）更具挑战性。在此，通过同时引入羧基官能化和孔隙空间划分，开发了一系列羧基官能化材料，其组成多样，从同金属的Cr和Ni到异金属的Co/V、Ni/V、Co/In、Co/Ni。Cr-MOFs在沸水中仍保持高度结晶性。前所未有的是，一种Cr-MOF能够经受10m NaOH和12m HCl的处理循环，实现游离 -COOH酸形式和 -COO碱形式之间的可逆相互转化。这些材料表现出优异的吸附性能，例如在1 bar和298K下对CO（100.2 cm³ g）和烃类气体（例如，对CH₄为142.1 cm³ g，对C₂H₆为110.5 cm³ g）具有高吸附容量，对苯/环己烷具有高选择性（高达约40），并且对CH₄/CO和CH₄/C₂H₆等气体混合物具有良好的分离性能。
