Reaction-Diffusion-Controlled Growth of Multifunctional Nanocrystals for the Simultaneous Detection and Uptake of Hydrogen Sulfide

Crystal engineering of stimuli-responsive nanomaterials under out-of-thermodynamic-equilibrium conditions provides a powerful route to program their structural and electronic properties for applications in environmental remediation. However, achieving control over crystal size, morphology, and conductivity remains challenging, as currently employed solvothermal and interfacial syntheses offer limited tunability and poorly defined structure-property relationships. Herein, we report a non-equilibrium reaction-diffusion (RD) strategy that enables spatially resolved crystallization of layered, intrinsically conductive metal-organic framework (cMOF) nanocrystals within a gelled medium. Mixing spatially separated molecular precursors under supersaturation conditions generates a continuous gradient of framework particles along the diffusion path, exhibiting distinct crystallinities, morphologies, surface areas, and electronic properties. Structure-property correlations reveal that cMOFs isolated away from the liquid-gel interface display higher crystallinity, larger BET surface areas (216 vs 127 m 2 g -1 ), and enhanced conductivity (8.1 vs 6.1 x 10 -5 mS cm -1 ), resulting in a 7-fold increase in hydrogen sulfide (H 2 S) uptake (1.26 mmol g -1 ) and a 3-fold enhancement in chemiresistive sensing response relative to their counterparts isolated at the interface. Taken together, these results establish a mechanistic foundation for RD-mediated crystal growth and demonstrates a generalizable strategy for tuning the morphology, electronic function, and sorptive properties in layered nanomaterials.