Highly efficient catalysts with enough selectivity and stability are essential for electrochemical nitrogen reduction reaction (e-NRR) that has been considered as a green and sustainable route for synthesis of NH 3 . In this work, a series of three-dimensional (3D) porous iron foam (abbreviated as IF) selfsupported FeS 2 −MoS 2 bimetallic hybrid materials, denoted as FeS 2 −MoS 2 @IF x , x = 100, 200, 300, and 400, were designed and synthesized and then directly used as the electrode for the NRR. Interestingly, the IF serving as a slow-releasing iron source together with polyoxomolybdates (NH 4 ) 6 Mo 7 O 24 •4H 2 O as a Mo source were sulfurized in the presence of thiourea to form self-supported FeS 2 −MoS 2 on IF (abbreviated as FeS 2 −MoS 2 @IF 200 ) as an efficient electrocatalyst. Further material characterizations of FeS 2 −MoS 2 @IF 200 show that flower cluster-like FeS 2 −MoS 2 grows on the 3D skeleton of IF, consisting of interconnected and staggered nanosheets with mesoporous structures. The unique 3D porous structure of FeS 2 −MoS 2 @IF together with synergy and interface interactions of bimetallic sulfides would make FeS 2 −MoS 2 @IF possess favorable electron transfer tunnels and expose abundant intrinsic active sites in the e-NRR. It is confirmed that synthesized FeS 2 −MoS 2 @IF 200 shows a remarkable NH 3 production rate of 7.1 ×10 −10 mol s −1 cm −2 at −0.5 V versus the reversible hydrogen electrode (vs RHE) and an optimal faradaic efficiency of 4.6% at −0.3 V (vs RHE) with outstanding electrochemical and structural stability.

Precise design and construction of catalysts with satisfied performance for ambient electrolytic nitrogen reduction reaction (e-NRR) is extremely challenging. By in situ integrating an electron-rich polyoxometalates (POMs) into stable metal organic frameworks (MOFs), five POMs-based MOFs formulated as [Fe x Co y (Pbpy) 9 (ox) 6 (H 2 O) 6 ][P 2 W 18 O 62 ]•3H 2 O (abbreviated as Fe x Co y MOF-P 2 W 18 ) are created and directly used as catalysts for e-NRR. Their electrocatalytic performances are remarkably improved thanks to complementary advantages and promising possibilities of MOFs and POMs. In particular, NH 3 yield rates of 47.04 µg h −1 mg cat. −1 and Faradaic efficiency of 31.56% by FeCoMOF-P 2 W 18 for e-NRR are significantly enhanced by a factor of 4 and 3, respectively, compared to the [Fe 0.5 Co 0.5 (Pbpy)(ox)] 2 •(Pbpy) 0.5 . The cyclic voltammetry curves, density functional theory calculations and in situ Fouriertransform infrared spectroscopy confirm that there is a directional electron channel from P 2 W 18 to the MOFs unit to accelerate the transfer of electrons. And the introduction of bimetals Fe and Co in the P 2 W 18 -based MOFs can reduce the energy of the *N 2 to *N 2 H step, thereby increasing the production of NH 3 . More importantly, this POM in situ embedding strategy can be extended to create other e-NRR catalysts with enhanced performances, which opens a new avenue for future NH 3 production for breakthrough in the bottleneck of e-NRR.

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Phenols are widely used for commercial production, while they pose a hazard to the environment and human health. Thus, investigation of convenient and efficient methods for the detection, discrimination, and degradation of phenols becomes particularly important. Herein, two new polyoxometalate (POM)-based compounds, [Co 2 (btap) 4 (H 2 O) 4 ][SiW 12 O 40 ] (Co-POM) and [Ni 2 (btap) 4 (H 2 O) 4 ][SiW 12 O 40 ] (Ni-POM) (btap = 3,5-bis(triazol-1-yl)pyridine), are prepared via a hydrothermal synthesis method.The compounds show a fascinating structural feature of a POM-encapsulated twofold interpenetrating dia metal−organic framework. More importantly, besides the novel structures, the compound Co-POM realizes three functions, namely, the simultaneous detection, discrimination, and degradation of phenols. Specifically, Co-POM shows an excellent colorimetric detection performance toward phenol with a detection limit (LOD) ca. 1.32 μM, which is lower than most reported colorimetric detectors for phenol. Also, a new colorimetric sensor system based on Co-POM can discriminate phenol, 4-chlorophenol, and o-cresol with ease. Further, Co-POM exhibits a photocatalytic degradation property for 4-chlorophenol under irradiation of visible light with the highest degradation rate at 62% after irradiation for 5 h. Therefore, this work provides the first example of a POMs-based multifunctional material for achieving the detection, discrimination, and degradation of phenolic pollutants.

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