Vapor-Phase Infiltration inside a Microporous Porphyrinic Metal–Organic Framework for Postsynthesis Modification

Abstract

Vapor Phase Infiltration (VPI), a technique derived from Atomic Layer Deposition (ALD) and based on sequential self-limiting chemistry is used to modify the stable microporous porphyrin-based Metal Organic Framework (MOF) MIL-173(Zr). VPI is an appealing approach to modify MOFs by inserting reactants with atomic precision. The microporous nature and chemical stability of MIL-173 enable post-synthesis modification by VPI without MOF degradation even with extremely reactive precursors such as trimethylaluminum (TMA) and diethylzinc (DEZ). VPI proceeds through the diffusion of gaseous organometallic reactants TMA and DEZ inside the microporous framework where they react with two kinds of chemical sites offered by the porphyrinic linker (phenolic functions and pyrrolic functions in the porphyrin core), without altering the crystallinity and permanent porosity of the MOF. 27 Al NMR, UV-vis absorption and IR spectroscopies are used to further characterize the modified material. Physisorption of both precursors is computationally simulated by Grand Canonical Monte Carlo methods and outlines the preferential adsorption sites. Impact of temperature, number of VPI cycles and pulse length are investigated and show that, Al and Zn are introduced in a saturating manner inside the MOF on both available reactive sites. Porosity prerequisite is outlined for VPI which is proven to be much more effective than classical solution-based methods as it is solventless, fast, prevents work-up steps and allows reactions not possible by classical solution approach.

Mixed-metal Zr/Ti MIL-173 porphyrinic metal–organic frameworks as efficient photocatalysts towards solar-driven overall water splitting

“…Previous study demonstrated an efficient diffusion of metallic precursors inside MIL-173 pores 45,48 .…”

Porphyrin and phthalocyanine-based metal organic frameworks beyond metal-carboxylates

“…Given the impressive robustness of the Zr-gallate framework, this material was further studied by several groups for a number of properties. We could demonstrate its compatibility with an ALD-derived technique for post-synthesis modification on both the phenolic and pyrrolic reactive sites 112 . Vapour phase infiltration was achieved using two kinds of precursors: diethylzinc (DEZ) and trimethylaluminium (TMA).…”

MOF-enabled confinement and related effects for chemical catalyst presentation and utilization

“…Ideally, bridging or terminal hydroxo and/or aqua node ligands can react with metal ions, labile inorganic complexes, or organometallic complexes, either in the condensed phase (often termed solvothermal deposition in MOFs (SIM)) or via molecular volatilization into the vapor phase (often termed atomic layer deposition in MOFs (AIM)) to accomplish chemical attachment. [89][90][91][92][93][94][95][96][97] Subsequent treatment with steam or H 2 S can yield node-grafted oxy-or sulfido-metal species -either as individual metal ions or as few-atom clusters. 98,99 A majority of the transition-metal elements and a handful of main-group metals have now been grafted in this way to Zr-MOF nodes.…”