Controllable Encapsulation of “Clean” Metal Clusters within MOFs through Kinetic Modulation: Towards Advanced Heterogeneous Nanocatalysts

Abstract

Surfactant-free tiny Pt clusters were successfully encapsulated within MOFs with controllable size and spatial distribution by anovel kinetically modulated one-step strategy. Our synthesis relies on the rational manipulation of the reduction rate of Pt ions and/or the growth rate of MOFs by using H 2 as assistant reducing agent and/or acetic acid as MOFformation modulator.T he as-prepared Pt@MOF core-shell composites exhibited exceedingly high activity and excellent selectivity in the oxidation of alcohols as aresult of the ultrafine "clean" Pt clusters,a sw ell as interesting molecular-sieving effects derived from the outer platinum-free MOF shell.

Metal-Organic Framework Composites for Catalysis

“…Reprinted with permission from Li et al 56 Copyright 2018, WILEY-VCH Verlag GmbH & Co. (D) Incorporation of Pt NPs in a UiO-66 MOF by means of an in situ one-step protocol with kinetic modulation by H 2 /acetic acid (top) and with no modulation (bottom). Adapted with permission from Liu et al 57 Copyright 2016, WILEY-VCH Verlag GmbH & Co.…”

“…65,66 Recently, Li and co-workers developed a kinetically modulated one-step strategy to construct Pt@UiO-66 core-shell composites through delicately controlling the assembly process by modulators and solvent (Figure 3D). 57 They employed H 2 coupled with dimethylformamide (DMF) to accelerate the rate of Pt ion reduction and acetic acid to slow down the rate of UiO-66 formation. Moreover, the DMF solvent could serve as a ''bridge'' to stabilize the generated Pt NPs by its soft C-N group and to anchor Zr 4+ by its hard C=O group.…”

Fe3O4 Nanorods Coated with ZIF-8 and Decorated with Pt Nanoparticles as Magnetically Actuated Nanoscale Stirring Bars for Catalytic Dye Degradation, H2 Production, and Hydrogenation of Olefins

“…Composed of metal nodes and organic connectors, the metal–organic frameworks (MOFs) own tunable pore environments, high surface areas, and unique size-selective properties, − endowing MOFs with extensive applications in the fields of biomedicine, energy and environment, photo-electrochemistry, food safety, catalysis, and so on. − More importantly, various MOF-based materials − are designed by compositing MOFs with other substances (such as carbon materials, metal particles, and polymers), greatly expanding the application scope of MOFs. − Excellent adjustability, special physicochemical properties, and synergetic effects bring MOF-based composites both multifunctional performance and widespread applications in catalytic reactions such as hydrogenation (HYD), oxidation, carbon–carbon coupling, CO 2 conversion, and H 2 production. − Generally speaking, external stirring is a frequently used tool to disperse MOF-based composite catalysts evenly into reaction systems. However, the dependence on external stirring also causes some undesired limitations to MOF-based materials, including (1) the diffusion and mass-transfer efficiency between reactants and MOF-based catalysts are still unsatisfactory for heterogenous catalysis under external stirring; (2) the poor mechanical stabilities make MOF structures liable to be broken under vigorous external stirring, which may bring about the degradation of reusability and even the loss of size-selective catalytic properties; , and (3) MOF-based catalysts with traditional external agitation are hard to be used in microscopic reaction systems such as tiny channels and droplets, which are critical for lab-on-chip, small-scale machines, or integrated preconcentrator gas sensor microsystems. , All these issues considerably restrict the further catalytic applications of promising MOF-based composite materials.…”

Pristine Metal–Organic Frameworks and their Composites for Renewable Hydrogen Energy Applications

“…[71] The onepot method is to directly mix the functional materials and the precursors of MOF,and control the nucleation and growth rate of the functional material and MOF, depositing MOF on the sur face of the functional material. For example, Li et al [72] used hydrogen (H 2 ) and N, Ndimethylformamide (DMF) to accel erate the reduction rate of platinum ions and used acetic acid to slow down the nucleation rate of UiO66. During the syn thesis process, the solvent DMF acts as a bridge to stabilize the formed Pt nanoparticles via CN groups but alsoanchors Zr 4+ via CO groups.…”