Nanoporous Designer Solids with Huge Lattice Constant Gradients: Multiheteroepitaxy of Metal–Organic Frameworks

Abstract

We demonstrate the realization of hierarchically organized MOF (metal-organic framework) multilayer systems with pronounced differences in the size of the nanoscale pores. Unusually large values for the lattice constant mismatch at the MOF-MOF heterojunctions are made possible by a particular liquid-phase epitaxy process. The multiheteroepitaxy is demonstrated for the isoreticular SURMOF-2 series [ Liu et al. Sci. Rep. 2012 , 2 , 921 ] by fabricating trilayer systems with lattice constants of 1.12, 1.34, and 1.55 nm. Despite these large (20%) lattice mismatches, highly crystalline, oriented multilayers were obtained. A thorough theoretical analysis of the MOF-on-MOF heterojunction structure and energetics allows us to identify the two main reasons for this unexpected tolerance of large lattice mismatch: the healing of vacancies with acetate groups and the low elastic constant of MOF materials.

Transparent films of metal-organic frameworks for optical applications

“…[23] HKUST-1 SURMOFs can also be used as well-defined model system for studying dynamic processes in MOFs. [24] In addition to this, hetero-layered SURMOFs with different composition and even different structures can be grown, [25][26] enabling various applications like the remote-controlled release from a porous container. [27] All these applications require thin films of very high quality with respect to thickness homogeneity, low roughness and low number of defects, which results also in a very high transparency of the MOF film.…”

Hierarchically Functionalized Magnetic Core/Multishell Particles and Their Postsynthetic Conversion to Polymer Capsules

“…20 Recently we demonstrated that LbL MOF growth is not interfered by changing the linker molecules after a desired number of cycles. 21 We used this approach to post-synthetically functionalize different MOF layers grown around magnetic particles using blue and red dye molecules.…”

SURMOFs: Liquid-Phase Epitaxy of Metal-Organic Frameworks on Surfaces

“…Wang et al have used the LBL spraying procedure to fabricate heterostructured SURMOFs, which consist of three layers of distinct isoreticular SURMOF-2 structures [43], despite a large lattice mismatch of approximately 20%. The XRD patterns for this material reveal a perfect [001]-related crystal orientation of all SURMOF layers.…”

“…Possible ligation vacancies of the metal nodes at the MOF-MOF interface can coordinate with residual acetate molecules which act like capping agents. Moreover, the low elastic constant of the MOF materials facilitates delocalization of the mismatch defects, thus reallocating mechanical stresses over a larger area [43]. …”

“…(b) SEMimage of a hierarchically porous SURMOF (Cu(bpdc) + Cu(ndc) + Cu(bdc)) after loading Eu(bzac) 3 bipy compound without additional gold coating on the surface. (Reproduced from[43]. Copyright 2014, with permission from American Chemistry Society.…”