A Titanium–Organic Framework as an Exemplar of Combining the Chemistry of Metal– and Covalent–Organic Frameworks

Abstract

A crystalline material with a two-dimensional structure, termed metal-organic framework-901 (MOF-901), was prepared using a strategy that combines the chemistry of MOFs and covalent-organic frameworks (COFs). This strategy involves in situ generation of an amine-functionalized titanium oxo cluster, Ti6O6(OCH3)6(AB)6 (AB = 4-aminobenzoate), which was linked with benzene-1,4-dialdehyde using imine condensation reactions, typical of COFs. The crystal structure of MOF-901 is composed of hexagonal porous layers that are likely stacked in staggered conformation (hxl topology). This MOF represents the first example of combining metal cluster chemistry with dynamic organic covalent bond formation to give a new crystalline, extended framework of titanium metal, which is rarely used in MOFs. The incorporation of Ti(IV) units made MOF-901 useful in the photocatalyzed polymerization of methyl methacrylate (MMA). The resulting polyMMA product was obtained with a high-number-average molar mass (26 850 g mol(-1)) and low polydispersity index (1.6), which in many respects are better than those achieved by the commercially available photocatalyst (P-25 TiO2). Additionally, the catalyst can be isolated, reused, and recycled with no loss in performance.

Designed Cluster Assembly of Multidimensional Titanium Coordination Polymers: Syntheses, Crystal Structure and Properties

“…However,t he documented Ti CPs or the so-called Ti metal-organic frameworks (TiM OFs) thus far are still relatively rare. [21][22][23][24][25][26][27] In fact, due to the high reactivity of the commonly employed Ti precursors, the controllable synthesiso f multidimensional Ti CPs is still challenging. Therefore, to develop as imple, universal synthetic strategy of Ti CPs is particularly necessary.…”

A [4+2] Condensation Strategy to Imine‐Linked Single‐Crystalline Zeolite‐Like Zinc Phosphate Frameworks

“…The newly formed −N=CH− linkages are responsible for the absorption at ν ≈1620 cm −1 (Figure ). The P−O vibrations appear at ν =1181, 1175, 1176, and 1177 cm −1 (Table ) as strong bands for compounds 3 – 6 , respectively . The M−O−P asymmetric stretching vibration appears at ν ≈1020 cm −1 and the symmetric stretching vibrations at ν ≈920 cm −1 (Figure )…”

“…The PÀOv ibrations appear at n = 1181, 1175, 1176, and 1177 cm À1 (Table 1) as strong bands for compounds 3-6,r espectively. [17] The MÀOÀPa symmetric stretching vibration appearsa t n % 1020 cm À1 and the symmetric stretching vibrations at n % 920 cm À1 (Figure 1) Scheme3.Acombined MOF-COF approach to zinc phosphate frameworks 3-6. Further evidence for the presence of framework imine linkages comesf rom the CP-MAS 13 CNMR spectra of the solid samples of 3-6 ( Figure 2a and FiguresS6-S8, Supporting Information).…”

“…An alternative strategy to build porous solids starting from D4R zinc phosphate cubanes would be by diligently combining the principles of both MOF and COF chemistries. Such an approach to extended framework structures would make use of metal–organic SBUs decorated with well‐exposed reactive organic functionalities (such as a −CHO group) that are amenable for condensation reactions with appropriate linear bifunctional organic molecules (e.g., p ‐phenylenediamine), yielding COF‐like MOFs . The details of successful applications of this strategy to prepare a new generation of framework solids are described in this contribution.…”

A Titanium(IV)‐Based Metal–Organic Framework Featuring Defect‐Rich Ti‐O Sheets as an Oxidative Desulfurization Catalyst

“…13 Ca nd 1 HM AS NMR of COK-47 S revealed the presence of methoxides,which have been widely observed as capping agents both on discrete Ti IV clusters,o n the Ti IV cluster in MOF-901 and on Zr-MOFs like UiO-66 (Supporting Information, Figure S20). [10,17,18] As in the latter example,t he methoxides in COK-47 S stem from reversible post-synthetic exchange with hydroxy groups during washing (Supporting Information, Figure S21).…”