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Thestructure of the nanoporous metal–organic frameworkCu3(BTC)2(BTC = 1,3,5-benzenetricarboxylate)with a variety of molecular guests was studied in situusing single crystal X-ray diffraction. By collecting crystal structuredata for a series of guests within the same host crystal, insightsinto the molecular interactions underpinning guest adsorption processeshave been gained. Adsorption behaviors are influenced strongly byboth enthalpic and entropic thermodynamic, as well as interpore steric(size-exclusion) effects, and we note correlations between guest attributesand these effects. Vapor adsorption measurements revealed a guestuptake capacity inversely proportional to guest size. Correspondingly,structural results show that guests reside in the smallest pores accessibleto them. Interpore steric effects for larger guests cause these tobe excluded from the smallest pores, and this corresponds to lowertotal uptake. Both hydrophilic and lipophilic small guests adsorbfavorably into the 5 Å diameter smallest pore of the material,with the number of guests in these pores dependent on guest size andtheir location, in turn dependent upon both guest–guest interactionsand competition between hydrogen-bonding interactions at the aperturesof the smallest pore and lipophilic interactions at the center ofthe smallest pore. Hydrophilic guests with lone electron pairs interactpreferentially with the coordinatively unsaturated Cu sites of thedesolvated framework, with the number of these depending on stericinteractions between neighboring bound guests and guest flexibility.Guest coordination at the Cu sites has a significant effect on theframework structure, increasing the Cu···Cu distancein the dinuclear unit, with the Cu3(BTC)2unitcell being smaller when guests that do not coordinate with the Cuare present, and in the case of cyclohexane, smaller than for thedesolvated framework. Overall, our comprehensive structural studyreconciles Cu3(BTC)2adsorption properties withthe underlying guest–host and guest–guest interactionsthat gives rise to these. [ABSTRACT FROM AUTHOR]

Yeelimite, Ca4[Al6O12]SO4, is outstanding as an aluminatesodalite, being the framework ofthese type of materials flexible and dependent on ion sizes and anionordering/disordering. On the other hand, yeelimite is also importantfrom an applied perspective as it is the most important phase in calciumsulfoaluminate cements. However, its crystal structure is not wellstudied. Here, we characterize the room temperature crystal structureof stoichiometric yeelimite through joint Rietveld refinement usingneutron and X-ray powder diffraction data coupled with chemical soft-constraints.Our structural study shows that yeelimite has a lower symmetry thanthat of the previously reported tetragonal system, which we establishto likely be the acentric orthorhombic space group Pcc2, with a √2a × √2a × a superstructure basedon the cubic sodalite structure. Final unit cell values were a= 13.0356(7) Å, b= 13.0350(7) Å,and c= 9.1677(2) Å. We determine several structuresusing density functional theory calculations, with the lowest energystructure being Pcc2 in agreement with our experimentalresult. Yeelimite undergoes a reversible phase transition to a higher-symmetryphase which has been characterized to occur at 470 °C by thermodiffractometry.The higher-symmetry phase is likely cubic or pseudocubic possessingan incommensurate superstructure, as suggested by our theoreticalcalculations which show a phase transition from an orthorhombic toa tetragonal structure. Our theoretical study also predicts a pressure-inducedphase transition to a cubic structure of space group I43m. Finally, we show thatour reported crystal structure of yeelimite enables better mineralogicalphase analysis of commercial calcium sulfoaluminate cements, as shownby RFvalues for this phase, 6.9% and 4.8% for the previouslypublished orthorhombic structure and for the one reported in thisstudy, respectively. [ABSTRACT FROM AUTHOR]