High-performance nonprecious electrocatalysts toward water splitting are in high demand but currently their development is still challenging. Here, we demonstrate that heterometallic two-dimensional (2D) metal phosphonates with improved catalytic activity and durability could be realized through defect engineering and heterometallic doping. The optimal electrocatalyst QAU-1-FeNi(1:2) exhibits prominent oxygen evolution reaction (OER) activity in alkaline electrolytes with a very low overpotential of 230 mV at 10 mA cm⁻² and a small Tafel slope of 47 mV dec⁻¹ and is superior to the commercial electrocatalyst IrO₂. Meanwhile, QAU-1-FeNi(1:2) shows outstanding stability for at least 20 hours and continuous CV scanning for more than 2000 cycles. In this work, a novel strategy of optimization of phosphonate based electrocatalysts by defect engineering and heterometallic doping has been proposed, which has significant potential in the preparation of catalysts for energy conversion applications.