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 mu mol & sdot;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.