Ultra-micropore Analysis The   term   ultra-micropore,   sometimes   also   super-micropore,   has become   commonly   used   to   describe   pores   smaller   than   1nm diameter   (micropores   in   general   are   those   smaller   than   2nm diameter).   Ultra-micropores   are   commonly   present   in   materials such   as   activated   carbons,   carbon   nanotubes,   zeolites,   metal organic    frameworks    (MOFs),    zeolitic    imidazolate    frameworks (ZIFs)   and   covalent   organic   frameworks   (COFs).   Their   presence is    often    fundamental    to    applications    and    can    be    extremely influential   to   capacity,   activity,   adsorption   behaviour,   functionality and   accessibility.   Typical   applications   include   battery   materials, adsorbents   and   filters,   catalysts   and   gas   storage   /   sequestration materials.    Whilst    micropores    are    frequently    required,    their specific   size   and   volume   must   be   tightly   controlled   in   order   to maximise   performance   characteristics.   Micropores   of   the   wrong size   may   cause   poor   performance   or   product   failure   due   to   low capacity, inaccessibility or pore blocking. Using    the    most    recent,    state-of-the-art    instrumentation    it    is possible   to   fully   characterise   micropores   for   their   volume,   surface area   and   size   distribution.   Together   these   describe   the   porous nature   of   a   material   and   allow   for   the   relationships   with   material selection   and   performance   to   be   established.   It   is   then   possible to    define    the    specific    porous    characteristics    required    from material selection, design, production or regeneration.

Key Applications Micropore size distribution, volume and pore area for: Adsorbent capacity, accessibility and retention Sequestration capacity, accessibility and retention Gas storage capacity, accessibility and retention Catalyst efficiency and activity Battery efficiency, activity and charge / discharge ability Filter efficiency and efficacy Determination of regeneration conditions and efficiency Investigations of atypical performance: effects of low capacity and retention Investigations of product failure: pore blocking Identification of optimum characteristics and materials selection Determination of production and fabrication conditions

At   MCA   Services   we   use   the   latest,   state-of-the-art   Micromeritics 3Flex    instrument    for    micropore    analysis    which    applies    the volumetric   method   for   the   measurement   of   adsorption   isotherms. Nitrogen   is   most   commonly   used   as   the   adsorbate   with   excellent results   and   the   capability   of   extending   analyses   to   measure   data in    the    mesopore    region.    Combined    micropore    and    mesopore analyses    are,    therefore,    possible    in    a    single    analysis    and extensive     data     reduction     and     reporting     methods     can     be employed   to   characterise   each.   With   some   sample   materials, when   unfavourable   interactions   between   nitrogen   and   the   sample surface   are   area   likely,   it   is   preferable   to   select   an   alternative adsorbate.   In   such   cases   argon   adsorption   is   a   suitable   analytical method. However,   when   samples   contain   ultra-micropores   smaller   than approximately   0.5nm,   nitrogen   and   argon   adsorption   become problematic    due    to    slow    or    incomplete    accessibility    to    the smallest   pores   at   the   analysis   temperature.   In   such   cases,   CO2 adsorption   is   recommended   as   this   can   be   used   to   characterise pores   as   in   the   range   0.32     -   1.0   nm   diameter   (depending   on analysis    temperature).    It    is    also    possible    to    combine    CO2 adsorption   isotherms   with   those   of   N2   or   Ar   to   obtain   a   complete pore   characterisation   throughout   the   micropore   and   mesopore ranges.

Analytical Options and Highlights Nitrogen adsorption for micropore and mesopore characterisation Argon adsorption for micropore and mesopore characterisation Carbon dioxide isotherms for ultra- micropore characterisation Nitrogen adsorption at 77K Argon adsorption at 77K or 87K Carbon dioxide adsorption at 258 – 298 K Micropore size distribution data (graphical and numerical) Micropore volume and surface area data Combination of CO 2 and N 2 or Ar data Data reduction by DFT and NL-DFT methods Comprehens ive degassing options

The   Micromeritics   3Flex   is   an   extremely   powerful   instrument   with cutting    edge    technology    and    a    wealth    of    information    can    be obtained   from   comprehensive   data   reduction   software.   Combined with   our   decades   of   experience   the   maximum   information   about your   samples   can   be   obtained   from   a   single   analysis.   At   MCA Services   we   are   always   happy   to   advise   the   best   analytical   option for   your   particular   samples,   applications   and   requirements.   We also   routinely   assist   in   data   interpretation:   selecting   the   most pertinent   reporting   data   and   relating   porous   characteristics   to your specific materials and requirements.