Coordination Modulation Method To Prepare New Metal–Organic Framework-Based CO-Releasing Materials

• Published in: ACS applied materials & interfaces 2018-09, Vol.10 (37), p.31158-31167
• Main Authors: Carmona, Francisco J, Maldonado, Carmen R, Ikemura, Shuya, Romão, Carlos C, Huang, Zhehao, Xu, Hongyi, Zou, Xiaodong, Kitagawa, Susumu, Furukawa, Shuhei, Barea, Elisa
• Format: Article
• Language: English
• Subjects: Aluminum - chemistry; carbon monoxide; Carbon Monoxide - chemistry; continuous rotation electron diffraction; guest inclusion; Ligands; metal-organic framework; Metal-Organic Frameworks - chemical synthesis; Metal-Organic Frameworks - chemistry; Metals - chemistry; Molybdenum - chemistry; solid-state materials
• ISSN: 1944-8244; 1944-8252; 1944-8252
• DOI: 10.1021/acsami.8b11758

Aluminum-based metal–organic frameworks (MOFs), [Al­(OH)­(SDC)] n , (H2SDC: 4,4′-stilbenedicarboxylic acid), also known as CYCU-3, were prepared by means of the coordination modulation method to produce materials with different crystal size and morphology. In particular, we screened several reagent concentrations (20–60 mM) and modulator/ligand ratios (0–50), leading to 20 CYCU x_y materials (x: reagent concentration, y = modulator/ligand ratio) with different particle size and morphology. Noteworthy, the use of high modulator/ligand ratio gives rise to a new phase of CYCU-3 (CYCU-3′ x_50 series), which was structurally analyzed. Afterward, to test the potential of these materials as CO-prodrug carriers, we selected three of them to adsorb the photo- and bioactive CO-releasing molecule (CORM) ALF794 [Mo­(CNCMe2CO2H)3(CO)3] (CNCMe2CO2H = 2-isocyano-2-methyl propionic acid): (i) CYCU-3 20_0, particles in the nanometric range; (ii) CYCU-3 50_5, bar-type particles with heterogeneous size, and (iii) CYCU-3′ 50_50, a new phase analogous to pristine CYCU-3. The corresponding hybrid materials were fully characterized, revealing that CYCU-3 20_0 with the smallest particle size was not stable under the drug loading conditions. Regarding the other two materials, similar ALF794 loadings were found (0.20 and 0.19 CORM/MOF molar ratios for ALF794@CYCU-3 50_5 and ALF794@CYCU-3′ 50_50, respectively). In addition, these hybrid systems behave as CO-releasing materials (CORMAs), retaining the photoactive properties of the pristine CORM in both phosphate saline solution and solid state. Finally, the metal leaching studies in solution confirmed that ALF794@CYCU-3′ 50_50 shows a good retention capacity toward the potentially toxic molybdenum fragments (75% of retention after 72 h), which is the lowest value reported for a MOF-based CORMA to date.