Exploratory research into the critical steps in metal-organic framework (MOF) activation involving solvent exchange and solvent evacuation are reported. It is discovered that solvent exchange kinetics are extremely fast, and minutes rather days are appropriate for solvent exchange in many MOFs. It is also demonstrated that choice of a very low surface tension solvent is critical in successfully activating challenging MOFs. MOFs that have failed to be activated previously can achieve predicted surface areas provided that lower surface tension solvents, such as n-hexane and perfluoropentane, are applied. The insights herein aid in the efficient activation of MOFs in both laboratory and industrial settings and provide best practices for avoiding structural collapse.

A 2D zirconium-based microporous coordination polymer derived from the tritopic linker 1,3,5-(4-carboxylphenyl)benzene, UMCM-309a, has been synthesized. This noninterpenetrated material possesses a Zr6(μ3-O)4(μ3-OH)4(RCO2)6(OH)6(H2O)6 cluster with six hexagonal-planar-coordinated linkers. UMCM-309a is stable in an aqueous HCl solution for over 4 months. The use of different monocarboxylates as modulators leads to similar 2D structures with different layer spacings; moreover, removal of the modulator yields the parent UMCM-309a.

A wide variety of charge carrier dynamics, such as transport, separation, and extraction, occur at the interfaces of planar heterojunction solar cells. Such factors can affect the overall device performance. Therefore, understanding the buried interfacial molecular structure in various devices and the correlation between interfacial structure and function has become increasingly important. Current characterization techniques for thin films such as X-ray diffraction, cross section scanning electronmicroscopy, and UV-visible absorption spectroscopy are unable to provide the needed molecular structural information at buried interfaces. In this study, by controlling the structure of the hole transport layer (HTL) in a perovskite solar cell and applying a surface/interface-sensitive nonlinear vibrational spectroscopic technique (sum frequency generation vibrational spectroscopy (SFG)), we successfully probed the molecular structure at the buried interface and correlated its structural characteristics to solar cell performance. Here, an edge-on (normal to the interface) polythiophene (PT) interfacial molecular orientation at the buried perovskite (photoactive layer)/PT (HTL) interface showed more than two times the power conversion efficiency (PCE) of a lying down (tangential) PT interfacial orientation. The difference in interfacial molecular structure was achieved by altering the alkyl side chain length of the PT derivatives, where PT with a shorter alkyl side chain showed an edge-on interfacial orientation with a higher PCE than that of PT with a longer alkyl side chain. With similar band gap alignment and bulk structure within the PT layer, it is believed that the interfacial molecular structural variation (i.e., the orientation difference) of the various PT derivatives is the underlying cause of the difference in perovskite solar cell PCE.

A design strategy based on geometric analysis of linker shape and flexibility is developed in the context of achieving predictable topology of tetratopic-linker based Zr microporous coordination polymers (MCPs). Tetratopic linkers are categorized into tetrahedral, planar square, or planar rectangular groups based on symmetry with an emphasis on linker flexibility. A prediction framework solely based on linker shape and cluster connectivity derived from this strategy is applied to all 18 reported tetratopiclinker based Zr MCPs, and their determined topologies fit well into the scheme. Two new Zr MCPs (UMCM-312 and UMCM-313) are produced using designed linkers based on the strategy to test the robustness of prediction. UMCM-312 contains a biphenyl-core based tetratopic linker to target tetrahedral shape, and UMCM-313 takes advantage of a perylene based tetratopic linker to achieve rectangular shape. The experimentally determined topologies confirm predictions. It is thus demonstrated that the uncertainty of targeting topologies in tetratopic-linker based Zr MCPs can be reduced by accounting for linker shape and flexibility.

Exploratory researchinto the critical steps in metalorganic framework (MOF) activation involving solvent exchange and solvent evacuation are reported. It is discovered that solvent exchange kinetics are extremely fast, and minutes rather days are appropriate for solvent exchange in many MOFs.Itisalso demonstrated that choice of avery lowsurface tension solvent is critical in successfully activating challenging MOFs.M OFs that have failed to be activated previously can achieve predicted surface areas provided that lower surface tension solvents,s uch as n-hexane and perfluoropentane,a re applied. The insights herein aid in the efficient activation of MOFs in both laboratory and industrial settings and provide best practices for avoiding structural collapse.