Size-Dependent Properties of Solution-Processable Conductive MOF Nanocrystals

Abstract

The diverse optical, magnetic, and electronic behaviors of most colloidal semiconductor nanocrystals emerge from materials with limited structural and elemental compositions. Conductive metal−organic frameworks (MOFs) possess rich compositions with complex architectures but remain unexplored as nanocrystals, hindering their incorporation into scalable devices. Here, we report the controllable synthesis of conductive MOF nanoparticles based on Fe(1,2,3-triazolate) 2 . Sizes can be tuned to as small as 5.5 nm, ensuring indefinite colloidal stability. These solutionprocessable MOFs can be analyzed by solution-state spectroscopy and electrochemistry and cast into conductive thin films with excellent uniformity. This unprecedented analysis of MOF materials reveals a strong size dependence in optical and electronic behaviors sensitive to the intrinsic porosity and guest−host interactions of MOFs. These results provide a radical departure from typical MOF characterization, enabling insights into physical properties otherwise impossible with bulk analogues while offering a roadmap for the future of MOF nanoparticle synthesis and device fabrication.

Crystal-size effect on the kinetics of CO2 adsorption in metal organic frameworks studied by NMR

“…Thus, the functions of the MOFs can be tuned by controlling the particle size and thereby the surface area, as well as by straightforward chemical modification. Indeed, many reports addressed the consequences of adjusting the particle size that manifest through macroscopic observations of, e.g., the catalytic activity, 6 adsorption efficiency, [7][8][9] optical properties, 10 shape memory, 11,12 and so on. However, little has been investigated about the particle-size effect from a microscopic, molecular perspective.…”

Oxidative control over the morphology of Cu3(HHTP)2, a 2D conductive metal–organic framework

“…4 In addition to higher mass transport rates, downsizing bulk MOFs to form colloidally stable nanocrystals may also provide important processability advantages. 5,6 This study focuses on controlling the morphology of Cu 3 (-HHTP) 2 (HHTP ¼ 2,3,6,7,10,11-hexahydroxytriphenylene), a prototypical 2D conductive metal-organic framework (Fig. 1).…”

“…4 In addition to higher mass transport rates, downsizing bulk MOFs to form colloidally stable nanocrystals may also provide important processability advantages. 5,6…”

Anisotropic Band-Edge Absorption of Millimeter-Sized Zn(3-ptz)2 Single-Crystal Metal–Organic Frameworks

“… 39 In this work, we study the absorption of large individual Zn(3-ptz) 2 single crystals across different crystal planes and discuss the size dependence of the anisotropy in the absorption spectrum with crystal samples of millimeter dimensions, thus extending previous work on the dependence of MOFs’ electronic properties with size over submicrometer dimensions. 40 Finally, we carry out solid-state density functional theory (DFT) calculations to rationalize the relationship between the crystallographic structure and optical response of our large single-crystal samples.…”