Data underlying the publication: Hybrid Microgel–MOF (M&M) Etalon Sensors for In Situ Detection of Dissolved CO2

The work presents a class of hybrid optical sensing platforms based on poly(<em>N</em>-isopropylacrylamide-<em>co</em>-methacrylic acid) (pNIPAm-<em>co</em>-MAA) microgels interlaced with MIL-53(Al)-NH₂metal–organic framework (MOF) nanoparticles for in situ sensing of dissolved CO₂(dCO₂). Using an in situ hybridization strategy, MIL-53(Al)-NH₂is uniformly embedded within the polymeric matrix, yielding microgel–MOF (M&amp;M) hybrids with tunable porosity, optical responsiveness to dCO₂, and structural integrity controlled by the cross-linker.<em>N</em>,<em>N</em>’-Methylene-bis-acrylamide (BIS)-cross-linked M&amp;M hybrid beads display greater rigidity, while poly(ethylene glycol)diacrylate (PEGDA)-cross-linked beads exhibit higher swelling ratios. Gas adsorption studies reveal reduced CO₂uptake compared to pristine MIL-53(Al)-NH₂MOF due to partial pore blocking by the polymer, yet the hybrid beads consistently outperform MOF-free ones, confirming that MIL-53(Al)-NH₂remains functionally active within the microgel network. Ultraviolet–visible (UV–Vis) absorbance experiments highlight distinct hybrid behavior with dCO₂, inducing clear decreases in absorbance linked to MOF-mediated swelling, in contrast to the negligible response of pristine microgels. Reflectance spectroscopy further demonstrates that M&amp;M-based etalons respond to dCO₂through characteristic red shifts driven by MOF-mediated CO₂adsorption and pore expansion, while MOF-free microgels show purely pH-driven blue shifts in response to dCO₂due to the acidic environment. M&amp;M beads with three different mass ratios between the microgel and the MOF are synthesized, among which the 5:1 hybrids with the BIS cross-linker exhibit the highest CO₂uptake and deliver the most stable optical performance, maintaining reproducible responses over three consecutive CO₂cycling tests.