Silicalite-1 zeolite enables graphitic carbon nitride high selectivity toward CO2 photoreduction

Carbon monoxide (CO) constitutes a pivotal chemical feedstock, extensively applied in diverse industrial processes such as the Fischer–Tropsch synthesis and the water-gas shift reaction, among others, underscoring its significant role in the chemical industry. Photocatalytic CO₂ reduction to produce CO provides an appealing route to consume useless greenhouse gases to valuable chemical feedstock. Regarding the poor selectivity of photocatalytic CO₂ conversion and the separation complexity for mixed products, integrating zeolite with semiconductor photocatalyst is first presented to achieve highly selective CO₂ photoreduction. Herein, silicalite-1 zeolite with high surface area and excellent CO₂ affinity is selected to construct a graphitic carbon nitride/silicalite-1 (CN/S-1) composite via a facile thermal polymerization procedure. The introduced S-1 zeolite enables extended visible light response, enhanced CO₂ adsorption, promoted separation and transportation of photoexcited charge carriers for the as-synthesized CN/S-1 composite. The resulting CN/S-1 composite shows significantly improved photocatalytic CO₂ reduction activity, yielding CO and CH₄ of 452.8 and 11.63 μmol·h⁻¹, respectively. The CO selectivity of the CN/S-1 composite achieves 97.5 %, which is maximal so far among the CN-based photocatalysts. In-situ Fourier transformed infrared (in-situ FTIR) spectra characterization reveals the composite prefer to dissociate COOH* to CO upon the incorporation of S-1 zeolite rather than protonation into hydrogenation products.