Selective　catalytic　oxidation　of　ammonia　(NH3-SCO)　to　nitrogen　(N2)　represents　a　pivotal　technology　for　abating　ammonia-containing　emissions　from　industrial　and　energy　utilization　sectors.　While　manganese　oxides　are　environmentally　benign　catalysts　with　notable　activity,　they　typically　afford　low　N2　selectivity　due　to　over-oxidation　of　NH3　to　noxious　nitrogen　oxides.　Herein,　an　efficient　strategy　integrating　microwave-assisted　hydrothermal　synthesis　with　boric　acid-etching　was　developed　to　construct　high-performance　MnO2-based　catalysts.　Boron　species　existed　as　MnBO3　on　the　surface　of　α-MnO2　or　occupy　the　interstitial　sites　in　the　α-MnO2　lattice,　with　their　distribution　determined　by　the　boric　acid　solution　concentration.　The　optimal　catalyst　exhibited　moderate　crystallite　sizes　for　boron-doped　α-MnO2　and　MnBO3,　high　Mn3+　and　oxygen　vacancy　content,　and　enhanced　moderate　acid　sites,　collectively　promoting　NH3　adsorption/dissociation,　providing　key　intermediate-　NH2　for　the　proceeding　of　i-SCR　pathway　while　inhibiting　the　formation　of　N2O.　Remarkably,　it　achieved　100　%　NH3　conversion　at　165　°C　with　95　%　N2　selectivity,　and　demonstrating　excellent　stability　and　water　resistance.　This　work　offers　a　cost-effective　approach　to　design　transition　metal　oxide　catalysts　for　practical　applications.　©　2025　Elsevier　B.V.