Tuning extreme anisotropic thermal expansion in 1D coordination polymers through metal selection and solid solutions

Abstract

The thermal expansion behaviour of a series of 1D coordination polymers has been investigated. Variation of the metal centre allows tuning of the thermal expansion behaviour from colossal positive volumetric...

Polytypism and Packing-Dependent Colossal Positive and Negative Thermal Expansion in a 2D Layered Cerium-Based Coordination Polymer

“…Since the PTE predominates, the crystal of α exhibits a very large volume CTE of +530.2­(15) MK –1 . It is worth noting that the negative and positive CTE values estimated exceed those for the majority of NTE and large PTE materials described to date. ,,− …”

“…In general, metal propionate complexes (MProp n L m here, L is an ancillary ligand) are valuable materials due to their unique structural features. Namely, flexible ethyl groups in propionate anions are able to rotate, which leads to unusual lattice dynamics and phase transitions. ,− Regarding the layered rare-earth propionates, one could expect a highly anisotropic thermal expansion with large positive and negative linear coefficients of thermal expansion (CTEs) that could be useful for the development of high-precision thermal actuators. − Indeed, many anisotropic coordination polymers are known to exhibit anomalous (anisotropic or/and negative) thermal expansion; − on the other hand, there are reports on colossal negative thermal expansion (NTE) promoted by the rotation or/and reorientation of certain structural units. − In particular, a combination of both factors gave rise to NTE for 1D-polymeric rare-earth pivalates where the negative α CTE of −128 MK –1 was reached . Furthermore, in general, CTEs are additionally packing-dependent. , Therefore, the studies of RE propionate polytypes and their thermal expansion represent significant interest.…”

Highly Robust Metal–Organic Framework for Efficiently Catalyzing Knoevenagel Condensation and the Strecker Reaction under Solvent-Free Conditions

“…Among the solid catalysts, the employment of heterogeneous catalysts is more advantageous than the homogeneous catalysts due to having several superiorities such as (i) easier catalyst recovery by filtration from reaction mixtures , (ii) reusable for consecutive runs , and (iii) their excellent adaptability to continuous flow processes . , However, to obtain the maximum efficiency of heterogeneous catalysts, a high surface area is required for more favorable interactions between the active sites of employed insoluble solids and the substrates and reagents. In this regard, metal–organic frameworks (MOFs) are the superior candidate over other solid catalysts, as they possess distinct superior qualities such as a high surface area with well-defined porosity − and innumerable structural diversity with suitable framework tunability. − MOFs exhibit superior catalytic activity due to the presence of several active sites such as (i) open metal sites (OMSs) , (ii) structural defect formations , (iii) bared functional groups’ presence of the employed organic linkers, and so on . Moreover, the synthesis flexibility and various binding modes of the metal centers (which often generate OMSs by mild activation) made MOFs promising candidates for heterogeneous catalysis.…”

Engineering Colossal Anisotropic Thermal Expansion into Organic Materials through Dimensionality Control

“…Modulating the solid-state property of thermal expansion (TE), which describes the response of a material to a change in temperature, − is of utmost importance for fabricating materials with extraordinary performance. − Depending on the intended application, specific TE behaviors are often required. For example, materials that exhibit large TE behavior are useful for thermomechanical actuators and sensors. − On the other hand, materials that undergo smaller changes in response to temperature alterations are useful in ceramics and aerospace applications. , In the field of semiconductor and composite materials, the TE behavior of all the components needs to be adequately matched to avoid device failure when temperature changes occur. − One significant challenge that materials scientists face lies in controlling a material’s structure, and this control is critical because structure directly influences properties. − Control over solid-state structure is often accomplished by directing atomic or molecular self-assembly and packing in all dimensions. − However, depending on the atomic or molecular building blocks, some dimensions may not be easily self-assembled with the assistance of strong interactions.…”