| Metal-organic frameworks(MOFs)feature as one of the most attractive class of materials in recent years with their characteristic structural diversity,designability,and high surface areas,enabling them as promising materials with applications in the fields of gas adsorption,catalysis,biological field,photo-/thermo-electrics.In the biologically-related field,MOFs are used as for efficient drug loading faciliated by the strong interaction between drug molecules and host materials that prohibits the drug leaking and pre-mature relase.Meanwhile,the low toxicity and bio-degradability of MOFs greatly reduces the side effects to enhance the life quality of patients during the therapeutic treatment.In this thesis,we synthesized nanoscale metal-organic framework(NMOF)UiO-66 rich in defects and subsequently utilized such defects for cisplatin pro-drug loading to achieve an enhanced loading capacity.We further elucidated the mechanisms of drug loading,drug release in the simulated body fluid,as well as the co-loading of the drug and single-stranded DNA.During the consecutive collaborative research,we also intended to venture the application of MOFs as a new class of thermoelectric materials,taking advantage of the ordered structure and inherent low thermal conductivity of MOFs.However,the low conductivity of MOFs hindered our investigation of their thermoelectric properties,and we eventually focused on the environmentally benign SnTe as the target thermoelectric material.The two independent parts of the thesis are thus briefly described as follows.I)In the first part,we synthesized UiO-66 NMOFs with designed defects and subsequently installed a hybrid phosphonoacetate ligand as facilitated by Zr-O-P linkages,leaving the carboxyl group free to anchor cisplatin prodrug cis,cis,trans-[Pt(NH3)2Cl2(OH)2].A drug loading of 256.5 mg·g-1(25.7 wt%based on cisplatin)is achieved with a Zr6:Pt:P ratio of 1.5:1:1,which surpasses defect-free UiO-66 and several other MOFs carriers.This work demonstrates that the MOFs defects can be intentionally engineered to achieve a high drug loading,and serves as an alternative to the drug encapsulation using the pore void or through association of the functionalized ligand.II)SnTe was regarded as an environmental-friendly alternate of PbTe thermoelectrics,whereas its performance is limited by its high thermal conductivity,partly owing to the high hole concentration.In SnT + exAgSbSe2,we observed a significant decrease of the total thermal conductivity from 3.37 W/mK to 1.27 W/mK at 850 K,even though the hole concentration is as high as 1021 cm-3.With the increasing AgSbSe2,both the electric and thermal conductivities reach their minimums at x?20%,and then they start to increase simultaneously,indicating a strong electron-phonon coupling.By applying first principles calculations,it is unraveled that the minimum of thermal conductivity is due to the non-monotonic dependence of electron-phonon coupling on the lattice constant.At x=20%,a ZT value of 0.953 at 850 K is achieved with an ultralow lattice thermal conductivity of 0.205.This study reveals that tuning electron-phonon coupling could be an efficient way to improve thermoelectric performance,providing it is constrained within the process of intra-valley scattering. |
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