To improve the solar energy storage efficiency and thermal conductivity, we developed stable 3D-Ti3C2Tx framework-supported composites as phase change materials (FCPCMs) fabricated by the spatial confining forced network assembly (SCFNA) method. The 3D-Ti3C2Tx framework was constructed by decomposition of a compressed mixture of NH4HCO3 and Ti3C2Tx nanosheets. The controllable porous structure of the 3D-Ti3C2Tx framework and hydrogen bonds between -OH groups (or -F groups) on the surface of MXene and the long chain of PEG benefited the good impregnation of PEG into the framework with good compatibility. Therefore, the developed PCM composites exhibited satisfactory phase change enthalpy in the range of 93.36–119.11 J/g. Compared with PEG8000, the thermal conductivity of the composite with loading 40 wt % of 3D-Ti3C2Tx increased from 0.166 to 1.733 W/(m·K). The improvement of the thermal conductivity is mainly derived from the thermal conduction path provided by the stable 3D-Ti3C2Tx framework. Based on the spatial confining forced network assembly, FCPCMs presented good shape stabilization and thermal reliability in 200 melting–freezing cycles. Benefiting from the construction of the 3D-Ti3C2Tx thermal conductivity path, the fast temperature increase rate under light irradiation is the highlight of FCPCMs. It is noted that FCPCMs exhibit both good photothermal conversion and energy storage efficiency, with the photothermal conversion and storage performance η as high as 95%. Consequently, the developed PCM composites in this work exhibited tremendous application potential in the solar energy utilization field.
Under hydrothermal condition, lactate derivative ( R )-4-(1- carboxyethoxy)-2-methylbenzoic acid (( R )-H 2 cma) as chiral synthon assembled with 4,4′-di(1H-imidazol-1-yl)-1,1′-biphenyl (4,4’-dib) and Ni(II) ions to obtain complex {[Ni 2 (( R )-cma) 2 (4,4’-dib) 2 (H 2 O)] ⋅ 2H 2 O} n ( HU20- R ). In complex HU20- R , carboxyl group from lactate unit of ( R )-cma 2− anion and coordinating H 2 O molecule adopt a μ 2 -coordination mode to obtain dinuclear [Ni 2 (CO 2 ) 2 (H 2 O)] 2+ cluster. ( R )-cma 2− anions and Ni(II) ions build single left-handed ( R )-cma-Ni-chain, while 4,4’-dib ligands are bridged by different Ni(II) centers to form double left-handed 4,4’-dib-Ni-chain. These helical secondary structures are further connected together to result in an 8-connected 3D framework. PXRD tests indicated that complex HU20- R has well hydro-stability. UV-vis absorption experiment confirmed that HU20- R is a semi-conducting material with strong absorption capacity for ultraviolet-visible (UV-vis) light. Additionally, electrochemical experiment revealed that HU20- R has low impedance and high charge transport capacity. Further test results confirm that HU20- R has noticeable photo-catalytic effect in photodegradation of Rhodamine B (RhB) and antiferromagnetic property.
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