AbstractDue to the weak nature of organic coordination bonds, metal–organic frameworks (MOFs) can hardly retain their intrinsic physicochemical properties and structural integrity when functioning in harsh heterogeneous reactions. Herein, a post‐synthetic strategy to reinforce the MOF structure by inserting siliceous linkers inside is proposed, according to which a Si‐infused UiO‐66 (s‐UiO‐66) with well‐developed porosity and exceptional thermal/structural stability is fabricated. This monodispersed Si‐infused matrix with enlarged nanopores is then utilized as the catalyst host, and is highly conductive to confining ultrafine CuO nanoparticles with uniform dispersion. Targeting CO₂ hydrogenation to methanol reaction, the Cu‐loaded s‐UiO‐66 (CuO/s‐UiO‐66) delivers a remarkable and efficient methanol production rate outperforming other Cu/ZrO₂‐based catalysts and the commercial catalyst. Moreover, the robust structure of CuO/s‐UiO‐66 prevents both copper phase and host material from aggregation during the catalyst preparation procedure and the reaction. In addition to material‐oriented studies, in situ characterization techniques are employed to identify the active Cu component and key intermediates formed during the CO₂ hydrogenation reaction, separately. It is envisioned that this Si infusion strategy can be applied to construct stable host materials with boundary‐defined structures from the pristine MOFs for broadened applications under extreme circumstances.