Crystal-to-Crystal Transformations of a Series of Isostructural Metal–Organic Frameworks with Different Sizes of Ligated Solvent Molecules

Abstract

Isostructural 3D metal-organic frameworks (MOFs) [Zn2(BTC)(NO3)S3] [where BTC = 1,3,5-benzenetricarboxylate; S = EtOH (1), DMF (2), DMA (3), or DEF (4)] of a 3-connected srs net topology have been prepared in the presence of serine as a template. The MOFs show different framework stabilities depending on the sizes of the ligated solvent molecules and undergo a crystal-to-crystal transformation at ambient conditions into a 1D chain structure either directly or via different types of intermediates depending on the ligated solvent molecules and the sample handling conditions. A single crystal of the MOF with the ligated DMF molecules, [Zn2(BTC)(NO3)(DMF)3] (2), is stable in Mg(II)- and Co(II)-DMF solutions; however, it transforms into a single particle-like microcrystalline aggregate of Cu-HKUST-1 in a Cu(II)-DMF solution.

Metal‐ion‐dependent, Solvent‐mediated Structural Transformation and Simultaneous Partial Transmetalation of an srs Framework into Desulfurization‐efficient Co‐Cu‐HKUST‐1

“…[23,47,51] In the Zn 2+ -based frameworks, either a monodentate or a chelating bidentate NO 3 rather than the Clin 1 is used instead. [23,51] In the synthesis of the Co 2+ -based framework, N,N-diethylformamide (DEF) molecules rather than DMA molecules were employed and the use of phthalic acid to adjust the pH of the synthetic DEF solution was proven essential. [48] In contrast, phthalic acid was proven unnecessary in the synthesis of 1.…”

“…It is worthy to note that [Zn 2 (BTC)(NO 3 )(DMF) 3 ], isostructural to 1, could experience a solvent-mediated structural transformation and simultaneous complete transmetalation to form Cu-HKUST-1 upon being soaked in a Cu(NO 3 ) 2 solution in DMF. [23] The driving force of such transformation could be that 2 is less soluble and more thermodynamically stable than 1. As 2 is formed, the dissolution equilibrium of 1 further shifts, resulting in the formation of more 2 and the continuous shift of the dissolution equilibrium of 1 and so on.…”

“…[11][12][13][14][15][16][17][18] Among few reports about solvent-mediated structural transformation with simultaneous transmetalation, incomplete transmetalation [19] is rarer than complete transmetalation. [20][21][22][23][24][25] efficient desulfurization adsorbent as the homometallic Cu-HKUST-1 in removing thiophene (0.142 mmol S per gram of adsorbent). However, when exposed to Zn(NO 3 ) 2 solution in DMA for longer time, 1 retained its framework with limited metal-ion exchange, resulting in the formation of [Co 1.93 Zn 0.07 (BTC)(Cl)(DMA) 3 ] (3).…”

“…For example, [Zn 2 (BTC)(NO 3 )(DMF) 3 ] can experience a solvent-mediated complete exchange of central metal ions to form Cu-HKUST-1. [23] Direct syntheses lead to heterometallic Cu-Zn-HKUST-1 and Cu-Ru-HKUST-1 with very small amount of Zn 2+ and Ru 2+ being included (Zn 2+ /Cu 2+ and Ru 3+ / Cu 2+ ratios are 0.03/2.97 and 0.25/2.75 respectively). [40][41][42] Previously Zn-HKUST-1 was converted into Zn-Cu-HKUST-1 via a crystal-to-crystal transmetalation mechanism in which the solvent merely supports metal-ion transport.…”

Structural Transformation Pathways of Alkaline Earth Family Coordination Polymers Containing 3,3′,5,5′‐Biphenyl Tetracarboxylic Acid

“…Obviously, the limited knowledge of crystal growth and the self-assembly process greatly restricts our capabilities of controlling structures, and developing more efficient synthetic methods. Recent reports [16,17] have demonstrated that the target crystal materials do not always proceed directly from the starting materials,i nsteado ft he metastable intermediates. Very few studies exemplify the step-by-step crystal growth process.…”