hatcher content part 6

why is porosity the most important property of mofs?

it provides very high internal surface area

what can pores in mofs be used for?

typically contain solvent (bound or free)

can be removed by heating and/or under vacuum (remember mofs have high thermal stability)

solvents can be exchanged

pores can accomodate guests (e.g. cf coordination cages and nanotubes)

how can the surface area of a porous material be determined?

adsorption isotherms e.g. BET analysis

extension to Langmuir theory (1916) by considering adsorption of multilayers of gas molecules

adsorption = adhesion of atoms or molecules of gas to a surface

what does the amount of gas adsorbed by a mof depend on?

the exposed surface area

the temperature

the gas pressure

strength of the gas-solid interaction

how is a bet measurement carried out?

measures the adsorption of a gas by solid mof

sample is placed in glass cell

mof is degassed by heating and vacuum and cooled

known amounts of gas adsorbate are injected stepwise into the cell at low temp

pressure transducers monitor the pressure changes due to the adsorption process

when adsorption saturates, sample removed and heated and N2 released and quantified

get bet adsorption isotherm volume of gas adsorbed vs relative pressure

what can mofs be used for?

reactions in mofs, gas storage/separation, chemical separations, guest encapsulation/exchange, heterogenous catalysis, photocatalysis, optoelectronics, sensors, drug delivery, nanofluidics

what are post synthetic modifications?

functionslisation of the mof after the crystalline material has been synthesised

what can you post synthetically modify on a mof?

the linker (covalent or dative/coordination psm)

nodes/sbus (inorganic psm)

guests (exchange of guests, e.g. counterions/solvents)

what are some common gases to be targeted for storage in mofs?

hydrogen, carbon dioxide, methane, ethyne

how can mofs be activated?

heating and vacuum - heat above bp of initial guest and apply vacuum, harsh conditions often cause damage to mof and/or collapse

solvent-exchange - soak mof in solvent of low bp than initial, gradual solvent exchange leaving pores intact, milder heating/vacuum process then applied to evacuate pores