Porphyrin aluminum MOF with ultra-high water sorption capacity: In-situ time-dependent ATR-FTIR spectroscopy and gravimetry to study mechanism of water bonding and desorption

Porphyrin-based aluminum metal-organic framework Al-MOF-TCPPH2 compound 1 is synthesized and activated to obtain 2. Its purity demonstrated by ATR-FTIR spectroscopy, spectral assignments of specific functional groups within the TCPP linker are provided as potential binding sites for adsorbate. Compound 2 reversibly sorbs desorbs significant amount water (up 50 wt. %) from humidified air it forms hydrated 3. 3 contains many up 25 molecules bonded several distinct in structural unit Al-MOF-TCPPH2. In exists small ice-like nanoclusters, which three-coordinated other fourth bond coordination surface d-H via their H atoms Further, NH group, carboxylate anion −COO−, phenyl group μ−OH group. facilely loses most its at moderate ambient relative humidity 45 %. During loss, nanoclusters with waters progressively transformed those four-coordinated denoted s-4. Chemical kinetics loss (desorption) has been investigated in-situ time-dependent gravimetric method under conditions. Kinetics reaction desorption follows pseudo-first order rate law constant. The spectroscopy demonstrates capability identify multiple sorption adsorbate MOF. Moreover, combination gravimetry a new unique experimental approach potential. This can be successfully utilized studies mechanisms reactions desorption, determination stoichiometry complexes sorbents adsorbate, chemical various solid-gas controlled environments.