Adsorption-Programmed Transformation of a Two-Dimensional Cu-Imidazolate Framework into Mn-Integrated Catalytic...

Metal-organic frameworks (MOFs) offer tunable platforms for water purification, yet the disposal of contaminant-loaded frameworks creates secondary waste and limits their sustainable use. Here, a circular adsorbent-to-catalyst strategy is demonstrated using a freeze-dried two-dimensional Cu-imidazolate framework (FD-BNMG-1). Prepared through scalable aqueous synthesis and lyophilization, FD-BNMG-1 removes more than 95% of Mn(II) from water within 24 h and reaches a maximum adsorption capacity of 370 mg g^-1, the highest reported for an unmodified MOF adsorbent toward Mn(II). Cu and Mn K-edge X-ray absorption spectroscopy, supported by powder X-ray diffraction, Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, scanning and transmission electron microscopy with energy-dispersive X-ray spectroscopy, and nitrogen sorption analysis, reveals that Mn sequestration drives substantial structural and electronic reconstruction. The Cu coordination number increases from 4.0 to 5.7, long-range Cu order is disrupted, and an open, redox-heterogeneous Mn-integrated Cu coordination nanonetwork is formed. Rather than being discarded, the resulting spent material, Mn@FDB, is directly repurposed as a heterogeneous catalyst for oxidative C-O cross-coupling reactions, affording aryl ester products in yields up to 84% and retaining activity over multiple cycles. This transformation demonstrates how adsorption can program a functional second life for contaminant-loaded MOFs. The approach integrates pollutant capture, material transformation, and efficient catalytic valorization.